Tuesday, May 27, 2008

Part III


I’m working on the mold for the body. I have only two more braces to ‘glass to the outside of the mold and I’ll be ready to pull it off the plug. Its very exciting and scary at the same time, not knowing what awaits me under all that fiberglass. I’m of course optimistic that it’ll be perfect but since I’ve never done this before, I just don’t know.

It sounds like we may have a local Speed Run day. I bought a radar gun and brought it up at a club meeting last night and there appears to be some interest. We’ll see what sort of problems we have finding a place to pit.

The weird thing is that even as I design and build this car I’m thinking of the next one, a complete reversal of what this one is. This one is very heavy and large, the next will be sleek and lighter. I’d like it to weigh half of what this one weighs, roughly five to six pounds. It’ll be front wheel drive, only two engines in line, rear wheel steering (maybe just with a rudder on the tail). It will be very narrow and long, a drooping nose with fuel tanks up front again and two widely spaced rear wheels mounted to a CF plate or wing with wheel pants. It’ll probably be a plagiarism of Gary Gabelich’s rocket car of the 70's. I’d like to try to get it as narrow as the width of two bullet tanks which is only about three inches. The front suspension could just be a plate upon which the engines and axle are mounted and held with a spring to the lower plate. If I flipped the diff so it ran backwards it would be FWD and the exhaust would go right out the back of the engine and the intake would be out front in the fresh air. Wow, I’m liking this car more and more! Jake said that he thinks the 134 record is breakable by nitro......maybe with this it would be!

New thoughts.....Both engines lateral, tied together on a gear/ shaft (maybe a two speed?) between them with a cog pulley on the other end, the belt runs the front tire/tires.

I pulled the plug out of the mold last night......sounds easy, right? Ummmm, not so. For some reason the mold release didn’t work so well in some places, mostly where I had the most plaster and had worked and painted it most recently. I cut the bottom of the tail off but I had to do that anyway to physically get it off. Then I cut out the cockpit and removed it with great difficulty. It took about 1/2 hour to get the rest of the mold off and even though it took big chunks of plaster with it, the portions I have cleaned are very smooth. I’ve got a lot of scraping to do but underneath all that paint and plaster is a good looking mold.I may try to make a body this weekend. The cockpit has to be glassed back in and a few very minor repairs made with bondo. The thing I didn’t do was wax the plug.....didn’t think I had to....so I’ll make sure to do that before spraying on the mold release, which worked well in the areas that it didn’t rip up the plaster.

The mold weighs 2-1/2 pounds which isn’t really indicatative of what the body will weigh but it surprised me. The first body is going to be a single layer of glass/resin in the interest of reducing that weight. If It’s too thin I can make supports inside with velcro to hold it up, like I would have to do with lexan anyway. This first body will also be a test to see how the cloth lays down in anticipation of a carbon fiber version.When I layed up the mold I did it with one sheet of mat and it was very difficult. With the bodies I’m going to do the top surface first with the lower tail section removed, making it easier to work the cockpit bulge. Then I’ll tape the lower tail back on and do the two sides, overlapping the top panel slightly. I might leave working the bottom of the tail until after the rest of the body has at least set up. I’m anxious to see the end results! It’ll be wicked awesome!

I got the mold cleaned up last night. It took about an hour to remove all of the left behind paint and plaster. It was a lot of work but could have been a lot worse.....at least at the end I had a workable mold! The cockpit was glassed back in and will require only minor touch ups to be ready to mold.

I laid out the engines and drive train for Problem Child II and it looks quite workable. The entire power assembly is very compact, utilizing less than one half of the existing layout’s parts. Just like the first I’ll add two more brakes but I’m going to run both the brakes and throttle with one servo. The steering servo will steer both the rear wheels and rudder, wheels for low speed, rudder for high. It’ll also have to have ailerons to keep the car from flipping during turns...front half car, rear half plane!There is one part that is going to have to be custom made and that’s the diff spool. Rather that the standard outputs I need 1/4" shafts upon which to mount the wheel hubs. In this way I’m eliminating the A-arms, shocks, springs, dog bones....the entire suspension and outer drive train systems! My thoughts are that most of the surfaces we’ll race on are smooth enough to not need suspension. I believe this car will weigh less than half of what the first version weighed with less than half the frontal area and surface....hopefully that’ll be enough to overcome losing half the power also!While it seems that thinking of a second car before the first is done deems the first to be a failure but the knowledge and technology of the first formed the development of the second. A quick look on line and I found a solid spool into which I can epoxy 1/4 axles for the wheels I’ll be using....excellent!

Well, I tried making a partial mold this weekend using the CF material I bought. It is amazingly flexible and I have high hopes about it. I tried using my dust collector vacuum but it didn’t have enough pull. Maybe I can use Uncle Bill’s old compressor’s intake to raise the vacuum. The mold was also not smooth enough and the part came out really bad but I saw where it needed improvement. I spent the last couple days working out the bumps and cavities in the mold and am now putting several coats of paint on it and then will wax the hell out of it and try a partial again before doing a total body.
I continue to design Problem Child II....ultra light, compared to #1, and aero smooth. I’m not sure whether to put the engines upright or lay them on their sides, either way requiring some sort of roll over protection. On their sides would lower the CG considerably and they would be protected by virtue of the car’s design.....I like it already. The throttles will need a unique solution but I’m sure that can be worked out.It would be nice to be able to use a tail from an existing plane but I don’t think that would work well. Better to design from scratch and get what I want even though it’s more work. I’d like to have the tail integrated into a spine for the rest of the car to give it some rigidity. That spine could be tied into the top plate which will connect the diff, engine mount and fuel tank plate...I’m likin’ this already too! The engines have to be moved a half inch or so to the rear to clear the tires but I think this can be worked out. I’m going to start another diary just for this car.

Work continues on the mold for the body. I have it very smooth now and with several coats of paint I should be able to put a slick enough surface on it to release the body. I found a source for the breather cloth and some vacuum fittings so I should be ready to pull a body next weekend. I have the carbon fiber cloth and may try to do a CF body first cuz its so easy to work with...its just costly. The intake on my shop compressor should have enough vacuum to do the job, just need to adapt a 1/4 inch hose to it.

I have run the dyno a bit and it seems to work pretty good. I hooked up the venom speedo so now I’ll have some real rpm data to work from. Right now it appears that the highest rpm the engines are reaching is 26k, not nearly enough for 110 mph. I’ll have to find the site I found that had all the engines on it and see what they were running so I can duplicate their power.

I’m having a heck of a time with the mold....cant get the paint to lay flat. Last night I put a thick layer on and will sand most of it off tonight. I want it to be as perfect as I can get it so the final body will also be smoooooth.

I ordered two Macs pipes for testing. I know they’re good so I guess I was buying the first parts for the next car or maybe try and fit them into this one. I’m optimistic that they will have a dramatic effect and assist me in getting to full rpm.
This weekend was somewhat productive. I sanded much of the paint off and put new primer on and filled any imperfection. I then put a new coat of paint on and it came out pretty nice. I’ll give it a couple days to dry and then sand and polish it, readying it for making a body this weekend....maybe.

I also ran an engine on my dyno but was somewhat disappointed in the results. The 11 inch prop is apparently just too big as it only revved up to 11,400 rpm and got the clutch very hot. I have a smaller 9 inch prop that I’ll try and see if it’ll rev higher. Then I can see if the changes I make are reflected in the power at the top end. The site I found listed the maximum HP and torque for the Picco at around 25K....hmmm....I’m going to stick with the gearing I have and work on the engines a bit before I change too much there. Get some real data once all four are pulling at full power.It has occurred to me that the reason I’m not seeing the big numbers I want is because the engines just aren’t revving that high. I’m going to run them all in on the stand with the 9mm venturis and 30% nitro for the next test day. Gotta get the rear wing back on, too.

I was just thinking.....I could maybe revamp the body to accept the Mac’s pipes which would aid in the revving department. A simple hump on each side would probably cover them. Might be necessary to aid in getting power.

I started sanding and polishing the form last night. Its coming out very smooth and will, hopefully, produce a smooth body. It’s been a lot of work, way more than I expected. In my world I would have pulled the plug from a perfect mold the first time, but that’s not how it happened.

In other news, the 11 inch prop was removed from the test stand and a 9 inch installed. This should allow the engines to spin right up and give me better numbers on different modifications. I’ll try it tonight and get smaller ones if necessary.Good news! The Mac’s pipes that were back ordered were sent out yesterday so I should have them soon. I think they will add a lot to the HP and rev range of my engines.

Finished polishing the mold last night, came out very good. Part of me wants to try a partial body to see how its going to work, part wants to not risk having to re-do the mold if it doesn’t come out smoothly. I think I’ll try the whole thing first time. The CF easily conforms to the shape so the only unknown is the epoxy. I’ll do a ‘dry run’ with the CF and vacuum bag to try and solve any problems then rather than when I have hardening epoxy in there. (use clothes pins at the edges to keep the cloth from folding over)Very exciting!!!!!!

I changed the prop on the engine stand over to a smaller version and then a new problem showed up! The shaft between the drive gear and the prop isn’t perfectly straight and at 12K rpm it started vibrating badly so I’m going to put a mid bearing on it to keep it from bending. I’m also gearing it down to 3:1 so the shaft won’t spin so high. I’ll put the bigger prop back on to provide some drag.

The mold is ready to go! I epoxied a couple tabs at the tail to align the bottom mold and it seems to have worked. All I have to do is tape the snot out of it to hold it in place and pray it stays there during the vacuuming.

Been a while since I checked in.....last night I got the dyno balanced out and hit almost 29k rpm with a 9 inch prop so I think I’ll use that as the standard. The mid bearing on the shaft worked beautifully and it just revved its heart out with no wiggling. I also moved the throttle back behind the engine and away from rotating stuff so my digits are safe. The engine also revved freely and I’ll rotate the rest through the stand. Some fresh 25% and the 9mm venturi made it very responsive. I’m waiting for some head gaskets to bump it up to 30 and then 40%....zoom!

While reassembling the car I noticed that the drive shaft was slightly bent and that’s not the first one to do so. I don’t think they can handle the power and found a Hardcore Racing upgrade on ebay for $10. Now that I have the radar gun I’ll take the venom off and replace the input cup so it’s balanced also(no magnet or hole) At 35K rpm any imbalance is bad and it may be aggravating the situation.

I put the Macs pipes on and there was no immediate, appreciable difference in the rpm. I would have to modify the body a LOT to fit them in so I’m going to save them for the next car. Uncle Bill’s old air compressor needed a new motor so that I could get enough vacuum to form the body. I got that done but haven’t had time to check if it has enough but I’m assuming it does...if it doesn’t its all I’ve got! So it better! I have to remount the air control valve and do a little wiring clean up and it’ll be ready to test.

I would like to maybe run it this weekend but I’m not sure I can do that. I really need to run each engine on the stand before I do. I’ve got a couple evenings and Friday and Saturday to do that and remount the wing....maybe I can get it done and run. I would like to get a full length run since I’m not really sure if it’s topped out or not.

Got Uncle Bill’s compressor going last night! and it had 25 inches of vacuum!!!!! If I have time after getting the car ready to run I’m going to try and pull a body. All of the veneering stuff I ordered came in so I just need some hose and some big diameter ABS for a storage tank and I’m ret ta go!
Okay, this was a weekend for learning. After attaching all of the hoses and valves I tested the system and it held 25 inches of vacuum for quite a while. I did a dry run with the CF and again, with the bag in place, it managed to get to 25 inches and held it, not quite as well as the hose alone. I decided to give it a try on Saturday. I waxed the form a few more times and applied the pva. After mixing the epoxy and hardener I brushed a coat into the form but it beaded up. Then I laid in the CF but the edges were starting to come apart so the width ended up a little short. I put second layers along the bottom edges and at the cockpit area. I didn’t do as good a job as I should have in making sure that all of the fabric was wet. Then I put it all in a bag, hooked up the vacuum fitting and turned on the pump.It seemed to be going all right, but I didn’t have the same level of vacuum I had before and it dropped off immediately if the pump was turned off so I left it running. I was able to find a couple holes and patched them which raised the vacuum to 20 inches but it still dropped off quickly. Lesson here - always use a new bag! I ran the pump for about an hour before turning it off and setting the form in the sun.When I took it out of the bag it was quickly obvious that there were some dry spots. Also the area under the tail was incomplete. I was in a big rush at the beginning when that wasn’t necessary. I need to take more time to make sure everything is soaked. I also need to put two layers everywhere for it to be strong. Its not bad with one but its kinda flexy.

All in all, it was a positive experience. I have to decide whether to try to re-do the original form or start over and make a new one with a gel coat finish. Each has its advantages and disadvantages. I have learned enough that I think I could make a much better form now with a nice gel coat surface which would make subsequent bodies better. I have the time since the meet isn’t until October....I think I’ll make a new mold. That way I can make the cockpit better, too. For the time being I’m going to patch up the first body and use it for testing purposes.I also am going to build a dyno stand with a couple heavy steel rollers. It’ll help me tune in the entire chassis, not just the engines. More later.

I’m hoping to run the car this weekend a little bit. I have gone through all four engines on the test stand to get the tune very close to where it should be in anticipation of next Sunday’s Speed Fest. My biggest goal is just to be able to run the car and keep all four engines running consistently. The engines are finally hitting full rpm and sound great. With someone watching both ends of the street I should be able to use the entire length and get up to a respectable speed.

I fit the body to the chassis and it looks good but it’s a big, heavy car. The heads don’t stick out quite as far as I though they would and I was able to cut the openings fairly close. Some tape will help refine those openings in the final body. It will be attached to the chassis with velcro down the sides and a couple flat spots along with a few body pins. If I can get the side dams attached I may try and run it with the body this weekend but only after trying some speed runs with the roll cage in place.

I am seriously looking for 100+ at the Speed meet. The right gears are in place, the engines are tuned, I know what the gear lash is supposed to be....highly confident that it’ll happen. All the pieces are in place..... but something comes along each time. I’ll install some new tires to eliminate the split one from blowing up. The new heavy duty drive shaft is in place (still need to buy an aluminum brake mount).......I’m tired of writing, I want to run!
I had ordered some tires for high speeds and asked Jake to contact BSR for recommendations. Well, rather than foams they sent caps.....I just asked for the same tires Nic was running. Although I’m a bit ambivalent about them, it may work out in my favor if the official run is done on a drag strip since foams apparently won’t hook on VHT whereas caps will. Can’t hurt to try them.....or can it?
The buzz is that I’m expected to have the body mounted so I’ll make an effort to do so. Shouldn’t be too much work, mostly reinforcing the body in a few places and getting the air dams on. Really looking forward to Sunday. Everything is ready to go fast......where have I said that before?
Got the body mounted last night and it fits just how I expected it to. I have to put a foam spacer between the tanks and front body panel to support it and will put another layer of CF on it to make sure it doesn’t bend up and start catching air at speed. Ran new exhaust pressure lines, eliminating a few fittings, so the car is ready to run as a bare chassis. All that’s lacking now is exhaust pipe extensions and the side dams......oh, and a few stickers.
I am so tired of working on this stupid car, thinking its all ready to go and every time it falls flat on its face. Once again engines were cutting out randomly, never the same one, so there is some common mis-tune somewhere. We even tried strapping the starter pack on it so the glows were on all the time, not much difference. I don’t want to give upon this thing but it is really getting the best of me!I have to build a rolling dyno so I can tune it under load. It will require two rollers about 15 inches long and three inches in diameter with the ends cut down for one inch bearings in pillow blocks. I’ll get the electronics to go with it later . This will also be a great tuning aid at any meet since it would let me tune the whole chassis in before making a run. The electronics would tell me what setting was getting the best hp and I could always get the most out of it. Right now I’d just like to get a decent run out of it.....
The rollers are presenting a challenge....to take a piece of 2-1/2 inch steel and turn it down for the one inch bearings is about $200 plus material. Or I can take a one inch shaft and slide a couple 3/8 tubes over it and tack weld them in place. If I can find the tubing that’s what I’m going to do.
Been a while since I wrote....did some real racing last Sunday. Got a third in nitro sedan (funny...THAT engine runs just great!) and fifth in electric sedan with a strangely dying pack. Had a good time though. Brought the Problem Child along to the dismay of lots of racers. Maybe next time I’ll bring the starter box along and fire it up.While at the race I furthered my acquaintance of John W, a machinist I met at a meeting. He has offered to do the machine work on my dyno rollers so if I pick up the bearings at Grainger I might have it running this weekend then I can start tuning!
Prior to tuning though I’m going to pressurize each engine and do the soapy water test for air leaks. There is something wrong there, just can’t find it and I’m hoping this’ll answer that question.
5/14/08 - Well, well, well......the front bearings are leaking air like there’s no seal in there at all. Wrote to Picco, they were no help, just reiterating on how leak free their engines are...blah, blah, blah. Jake is going to get some Boca bearings for me and that should solve that problem.I picked up the steel on Monday and will drop it off at John’s house this evening. Hopefully I’ll be able to get the bearings soon. Jake has offered to help me tune the engines once the dyno rig is up....the more the merrier, I say!
Got a couple of the roller bearings today. They’re sealed and had a lot of drag. I popped the seals out and trimmed the inside lip so now there is very little drag. I’m looking forward to getting this thing up and rolling!5/20/08 - Not much new right now. I’m hoping that John will deliver my rollers at the meeting tonight so I can build the dyno. I managed to find a supplier for Picco parts so was able to order some head shims for the 40% and new orings and things. I also had to buy a new butane soldering iron as I dropped mine and snapped the plastic tank off. No new front bearings yet. Did manage to buy a small lot of Impulse parts for my Serpent and some more Hardcore parts for the scale TC3 I’m building on ebay....$60 for about $200 worth of parts.
On the down side, there’s no news coming out of R/C Car Action about this year’s event. It would be very disappointing if they didn’t continue what they started. There is a small group wanting to put on an event in Houston and although that would suck cuz it's so far away, it would at least be an event. Could also be disastrous.....
Still waiting on the rollers. John’s doing the machine work for next to nothing so I don’t mind waiting. I received the head shims yesterday so I can run 30-40% nitro. Jake was unable to find the front sealed bearings so I'll get them from Boca directly. Then I have to tear each engine down completely to install the new bearings and head shims. During that time I'll finish the dyno so hopefully everything will come together at the same time. We're going to try to have a speed run on June 22nd. I'd sure like to have it ready to run then.

Monday, May 26, 2008

Part II - The story continues......


The plan for this next weekend is to tune in the other two engines and maybe do a two engine pass with the front pair just to see how everything is working and then maybe try for four again. I may have said it before but this is a very trying experience. Even my wife is feeling sorry for me! I certainly hope there is some sort of personal reward at the end!!!!! The power switch was replaced with a higher quality toggle unit and the front end damage repaired. All that appears to have happened is the bolt snapped off from the tank mount and the fiberglass sheet jammed back a quarter inch or so. A couple new bolts and everything was ready to go again. The plate is buckled but poses no problem as is. I need to get in the habit of two things when starting the car for a run.....the first is run the servos to make sure both the throttle and brakes are operable and the second is setting the failsafe mode in the receiver.

The other safety thing I need is a throttle return spring between the brakes and throttle servos. Both of this weekend’s accidents would have been avoided by these checks. On Saturday I would have seen that the brakes were unplugged and Sunday the brakes would have brought the car to a halt in short order. Live and learn!!!!! All of the problems I’ve had have been minor because of the low speeds involved. Had any of them occurred at the speeds I’m expecting each could have been catastrophic. Like the initial incident with the brakes unplugged...there’s no way the car would have gotten stopped without hitting something. Likewise with the defective switch. If the car had been at full throttle and THEN hit the drain wall........well, I’d still be sweeping up pieces. It all comes back to working out the bugs with one engine instead of four....four engines running badly enough to keep speeds low..... potentially dangerous incidents happening at low speeds....it’s like dad is watching, making sure its successful in its own time, keeping it from destroying itself.

In preparing for this next test I have plumbed up the remaining tanks and re-installed the front wing. I also disassembled the carb of the engine that didn’t rev up and there were no obvious problems with the exception that I was adjusting the idle and idle mixture with the wrong screws. I now have a good working knowledge of the engine so tuning should go easier. I have also changed all of the engine mounting nuts over to wing nuts, allowing for easier engine adjustments and changes.

I am so sure that this weekend is going to be successful that I’m starting to think about the body. The first consideration is what to make it out of. My four choices are lexan, ABS, fiberglass or carbon fiber.

The pros /cons are as follows :


clear so it paints well/ not sure it can be vac formed
keeps a nice shine/ not sure it can withstand 100+ mph
crack resistant/ expensive & I can’t form it


cheap/ not sure about crack resistance
can be vac formed /painted on exterior


I can form it /might be a bit heavy
fairly cheap /painted on exterior

Carbon fiber:

WAY COOL /might be a bit heavy
I can form it /expensive
no need to paint /potential radio interference
can make either FG or CF with same form

Next thoughts are shape. I did a drawing of it but didn’t care for the tail. I will probably emulate Thompson’s Challenger tail..... since it worked for him it should work for me. I’ll have to hinge something so that I can start the engines and do fine tuning without removing the whole body. Maybe just leave a slightly enlarged hole in the top of the body. I would really like to use CF but there may be radio problems. I have a piece of CF in which I’ll drill a hole and then experiment with the radio’s range. If it works that’s gonna be the choice. I could even fake in a body with that sheet using hot glue....brilliant!

Jan 23, 2008- Got a lot of testing and tuning done this weekend. Prior to going I had to change the low gear on the front two-speed as it got chewed up. It appears that the engines move away from the gears and causes their failure so I’m going to set them up with no clearance and assume that some clearance will come in under power On Saturday I went to tune the left set of engines and they ran okay but again, not consistent.

There was one incident but fortunately the brake return spring I installed last week came into play and the car bumped the curb with no damage when the battery supply plug worked its way out of the receiver. I decided to pick up and head home in one piece. Sunday morning I was back out to test the right rear engine that I sealed up. It seemed to run better with a hotter plug but still not strong at top end. I decided to try to run two engines and installed the front pair. It pulled well but when the rpms got to the point of real power the second gear clutch seemed to slip. I had reduced the face to reduce weight in an attempt to raise the shift point but it appears there isn’t enough surface to provide sufficient surface area so I’m going to replace them with full face and stiffen up the springs. I got into the mid 70's (speedo locked up) with second gear going in and out. The gear with no clearance is still like new but the one with a bit of initial clearance is toast.... learned something there.

I went on line and found a site with info on the Picco engines and they recommend sealing them up with silicone. I have done one but am working my way through the rest. I am optimistic that this will help in the tuning department. I have also ordered some new gears, some regular nylon R/C type and a couple pairs of delrin gears. They will be stronger and may chip before they bend over like the nylon gears. There may be some brass ones in my future...... It’ll be a couple weeks before I test again. The engines need to be gone through, new gears and clutches installed and a headliner kit needs to go out. I am optimistic that big speeds are right around the corner.........

1/29/08 - So far I have sealed up two of the engines and repaired a broken exhaust manifold. I also put epoxy beads on the mufflers so the couplers won’t slide off. The new gears showed up yesterday and I’m anxious to see how those made of delrin hold up. New clutch shoes have been purchased and are ready to install. Tuning wise, I have spoken or emailed a few folks in the know and feel like I have a better working knowledge of how these things run. Hopefully I can go through one more tuning session and then run all four. The overriding problem right now is weather....nothing but rain, rain and more rain. Maybe I can get the gears and clutches in and the engines sealed in time to run this weekend..... and maybe not. Not gonna kill myself to get it done. The starter box was also starting to act up again. The box uses a very simple washer to contact two tabs to switch the engines on but there is considerable arcing at start-up which has rendered them toast. I am going to install a Ford starter relay to run the starter motors and then the washer switch will only activate the relay’s very low amperage. Supposed to rain this weekend.....no running happening then!

It’s been several days since I even worked on the car. My wife's 50th birthday party was a LOT of work and fun and worth every minute. I am going get back to work on the car tonight and maybe be able to run tomorrow (2/12/08) I’m anxious to see what difference the sealing, my newfound knowledge, new gears and new clutches will make. One of these days the combination will work and success will be mine!! All mine!!!! Bwwwaaahaaaahhhaaaaaa

I got one night to work and hooked up the solenoid in the starter box ... it works great but the contacts are still a little inconsistent. When contact is made power is there. I also installed the new clutches and found a bad bearing in the front high gear housing so exchanged the bearing from another damaged housing. I also changed out the rear gears to delrin in anticipation of their success. Still waiting to work on the car. Every evening there’s something to do or its just too cold. Tonight I’m taking my wife out to dinner so I don’t mind missing tonight for that. I’m off tomorrow and for the next 17 days so I’ll be able to get a lot done. I’m going to get it back together on Sunday while I watch Daytona so I’ll be ready to maybe do some practice on Monday if there’s no traffic out at the test site. I’d also like to get started on the body since the basic layout of the car is finished. Maybe I can get the plug cut out of plywood and finished....maybe even get a rough mold pulled off of it. Gotta figure out how to vacuum the form also. Also need to repair the rear wing mounts, maybe make a nose out of stiff foam.

Well, back from vacation and a lot got done! I replaced all of the nylon gears with delrin and spent some time tuning each engine. All four are mounted and ready to run! The throttle servo started going wiggy, and eventually got stuck at wide open. Fortunately, the car wasn’t running at the time and I replaced it with a new one. The brake servo also started getting weird so I replaced it also, both servos being much stronger than the originals.

The side by side pairs of engines are now tied together with a brace between the heads. Under power the engines actually twisted away from the spur gears but now they’re very stable. I hooked up the four front tanks to the front engines (two each) and mounted two new tanks at the rear for the rear engines. This has allowed much shorter fuel lines which has made the engines run more consistently.

I managed to get the plug done and am ready to make the mold. I bought all of the fiberglass, resins and gel coat. Hopefully this weekend will provide the time to do the mold. The plug is made of two 4x4's of fir and three pieces of redwood between them, ending up with a body 9-3/4 inches wide, enough to cover everything. The two different woods has caused a problem by causing the joint between the woods constantly show up on the plug. If I fill it and paint it right away it’s invisible but as soon as it sits for a couple days its visible again. Minor, but irritating!

It turned out nicely and is very reminiscent of Mickey Thompson’s Challenger...can’t wait to run it! My goal is to make everything as aerodynamic as possible. This is an area that other racers have discounted as not important but I can’t believe that it doesn’t have the same effect as it does on full scale cars. There will be very small gaps between the body and chassis pan and the mounting screws will be as flush as I can get them, maybe small dzus fasteners. Hopefully this will counter balance any horsepower shortage I may have.

There are already claims of 100 mph so I’m going to set my sights to 110. This may require new gearing but I’m not changing anything until I run at Willits airport and get a true idea of the car’s speed. As I’ve been working on these engines, I really have no idea what RPM they’re running or if they can pull full power at full speed. I also have a question about the mufflers....are they a help or a hindrance? Once I get some nice runs on the engines I should pull one out and set it up on the bench, put a prop on it and run it through it’s paces. I could test venturis, carb settings and mufflers while checking its rpm range. Sounds like something I definitely have to do before going south!

03/09/08 - Got to run today! Put all four in and went to the site . I was rushed and left the radio at home, had to go back and get it then later realized the temp gun was sitting on the bench also. Gotta make a check list. Have I said that before? Prolly......

Started all four and set it down for a few slow passes. It was running great but came in on three so I thought I’d give it a run anyway. The rear wing mount broke a while back and I hadn’t repaired it yet thinking it was heavy enough so made the passes without it. All was well until decided to go for broke on a run and hit the brakes to slow down. At 87 mph it started spinning down the road, fortunately the road had enough dirt on it to minimize traction and it didn’t flip. After gathering myself up I packed up and went home.

Yesterday, I picked up a couple propellers and I’m going to build a bench test rig to allow me to tune the engines in at speed one at a time. I tried doing it in the car but it’s difficult to discern what’s happening as it drives by. It’s also time to step up to the 9 mm venturis. The 7's seem to be holding it back so let’s open it up. The clutches worked great, shifting and staying in gear. I’d like the shift point to be a bit higher so I’ll experiment with tightening the screws more. The delrin gears held up nicely except for the one where the screw backed out so I replaced it and put loctite on the screws (shoulda done it the first time). I fabbed up a four plug starter pack so I can run all four plugs at the same time. It’s much easier to keep them all running that way. My ampped up starter box worked great all day, never failing me once. All in all, it was a fun couple of hours. Again there were lessons to be learned....like the back wing......and the checklist.......and the temp gun.

Over the last couple evenings I designed and built a jig to allow me to bench test my engines under load out of the car. I thought that using a propeller for the load was pretty simple but one of the problems was how to mount it on the engine. I decided to mount the prop on a shaft and drive it from a gear on the other end of the jig, keeping fingers away from the prop blades. It also eliminated the need to remove the clutch from the engines, instead just meshing the gears as in the car. The plate that all this is mounted on will be bolted to the top of the starter box to allow easy starting of the engine while tuning. Can’t wait to try it out! Pretty simple and it should help me tune in the top end on the engines since that’s where all of my interest is. I’ll be switching over to the 9mm venturis and 25% nitro so it’ll be nice to be able to tune the engines before making any runs.

I also want to compare a Macs tuned pipe to the pipes presently on the car to see if there’s a significant difference. I don’t want to start changing the body to accommodate some new exhaust but in light of new competition I may have to. A lot of progress made this week..... I got my engine test stand built and it works well. I mounted it right to the starter box making the tune up procedure easier. The first engine on there runs good but doesn’t seem to be revving very high. I think this is going to be very productive as far as top speed goes.

Friday, May 23, 2008

Part I - I started this diary in September of '07 and just began this blog so I just pasted the whole thing here. As soon as I'm able to figure out how, I'll post some photos as well.
I picked up my first R/C magazine in a couple years for a flight to Seattle and was settled back in my luxurious coach seat when I saw an article on the World’s Fastest R/C Car Challenge. Just like a crack addict, I was instantly hooked. The present nitro record is 88mph....heck, I could beat that easy! By the time we landed I had my car designed.....a four-engined, nitro TC3. That center shaft was just begging to have more engines attached to it. Did I really need four engines? Probably not but what’s yer point? Remember, some’s good (.12 engine), more’s better (.21 engine), too much is just enough (two .21engines), and if in doubt, double it! (four .21 engines!). See? It was simple math.

I was completely possessed by this project. I had a hard time sleeping, thinking about what parts needed to be made, what parts could be bought. I have been building R/C chassis and parts for 20 years and it was as if this was to be my destiny. As soon as I got home I was on eBay and bought three junker TC3's. When they arrived they were disassembled and it was quickly obvious that the ring and pinion in the diffs were the weak point as the gears in four of the six were toast. I weeded my way through piles of parts, tossing some that were bad, cleaning the remainder.

Then came the real design work. The official nitro record is 88mph......what was I shooting for? The official electric record is presently 127mph although the holder, Nic Case, has run an unofficial 141!! I don’t think a nitro car is going to beat that simply because of the weight and the necessity for air to the engine(s), causing drag so my goal was somewhere between 88 and 127. So I set my goal at 100mph but my gearing has the potential for 117 at top rpm. I found large steel gears for the two-speed pinions (36 and 48 teeth!) which would require me to drill and tap them for the Associated clutch bells.

The chassis was laid out using two aluminum TC3 pans. I pulled the .12's out of my regular racers and put them in place. The four engines were going to be set up as pairs, front and rear, each pair driving a common spur gear. I was initially going to just put a second spur gear on the drive shaft but it was quickly obvious that wasn’t going to work. Instead, the front portion of one chassis pan was trimmed off at about the centerline of the rear axle. The two speed was left in its original position (but with no differential) and then the rear portion of a second pan was cut and welded to the tail of the first with the second two-speed assembly and differential. This stretched the wheelbase considerably for stability and a mish-mash of Associated parts cobbled from the three junkers finished up the drivetrain.

My plan was to use the aluminum pans for an initial test and then duplicate the mounting points onto a sheet of carbon fiber for the final stage. I mounted all the chassis parts and things were really looking good. I brought it down to Jake’s for his comments and while looking at it he very easily gave the now very long chassis quite a twist.............dang! That’s not good at all. Back to the drawing board.

Although the aluminum chassis was short lived, it was crucial for the location of parts and working out the very concept of the project so it was worth trying that way first. I had a piece of G-10 fiberglass onto which I transferred all of the mounting points, then drilled the holes and installed the parts. A thin top plate between the diffs worked wonders in stiffening the whole works. Wheel cutouts were removed, suspension bolted on and all of a sudden, it was a roller!

What engines to run was quite a quandary. I did internet research looking for the best power to weight ratio. In chatting with the present nitro record holder (Tony Lovering in the UK) .21 engines were recommended as the best candidates. There are a LOT of engines available, some with good power but a lot of weight, others with claims of great horse power debunked by independent dyno tests. I settled on Picco P9, Evo 2 engines. Picco claims 2.5 hp, and even thought a dyno test came up with 1.5 hp, it still had the best power of the .21 engines tested and was considerably lighter than the others. I could only afford one at a time over a couple months and Jake had to scour the country for the last one! I’m hoping that somewhere between six and ten horsepower is enough!

As things continued to come together other problems reared their ugly heads like, how do you start four engines at the same time? I scored a starter box on eBay for $6.50 and have set up pegs on it that match holes at each engine station so I’ll start them individually. Then, what if it flips? A full roll cage needed to be fabricated from thick music wire around the engine heads so if it does get on its lid those very expensive heads will be somewhat safe. I have had to accept that ANY crash approaching 100mph is going to be costly.

Another safety feature being developed is a drag chute. Now, besides looking too cool for words, if something goes completely awry merely letting off the throttle will release it, dissipating energy. Its set up so that once wide open throttle is achieved, a cog on the brake’s servo releases the chute when the throttle returns to idle. Any throttle setting less than WOT won’t release it. I’m anxious to see this work!

Although much of the car is low tech like the basic fitting of parts and pieces, there is some high tech on it..... a gyroscope. This is R/C helicopter technology used to keep these high speed cars straight. They take thousands of samplings per second and, with a high speed servo, constantly make adjustments to the steering so it stays on the course you choose.

Making all of this stuff work together is half the fun. An unusual project like this requires more than just out of the box thinking, it takes ‘that’s just crazy enough to work’ thinking! The four carbs are connected by cranks and rods to the throttle servo and the three disc brakes have a separate servo at the back of the car. One small fuel tank at the front of the car should feed the engines for the two or three minutes each run will take and the receiver pack is at the very back. The front engines’ mufflers go to the back, the back engines’ to the front. There are lots of wires and hoses to run, connecting all of the carbs, servos, controllers and exhaust pipes.

Piece by piece, the Problem Child came together. There were very few ‘do-overs’ needed and everything went together pretty easy for a project this complicated. After a couple months work the front two engines were ready to fire. On the starter box it went and with my finger over the exhaust to prime the carb I pushed down on the car. The engine spun for a few seconds and then we had one running engine. I let it run for several minutes, allowing everything to get warmed up before stopping it. I repeated the procedure on the other engine, running it for several minutes but then instead of shutting it off, I restarted the first engine ............what a glorious sound!!!!!! A blip of the throttle brought loud and instant rev response. The only thing I can liken it to is a top fuel dragster warming up in the pits. I ran the engines up to 60 mph and everything was very smooth. My original plan was to have two engines ready for a test on December 9th. I had other commitments which postponed the test for a week so now I had time to mount the other two engines.

Because I had worked out all of the details on the first pair the second pair went in fairly easily. I mounted the gyro and high speed steering servo and had to work out the common fuel and exhaust pressure lines. I welded up a roll cage to protect those very expensive heads and then fired up all four engines. If there’s such a word, it was an even gloriouser sound!

The day before the official test the car was run on a short side street to work out any bugs...and there were a few. One was the plethora of batteries that have to be charged prior to running - transmitter, receiver, starter and glow plug starter. Nothing wants to work so load everything back up, head home and charge all the batteries.

I returned a couple hours later and easily got the engines fired up. It was cold outside so they didn’t want to get to operating temps but once they hit 160-70 I set on the pavement and it moved under its own power for the first time. It had decent acceleration and I ran it up and down the street at moderate speed to try and warm it up but a problem immediately became obvious. That little tank could not feed those engines for long, at all! I could only make one or two passes down the street before re-fueling and then I usually had to start a stalled engine.

My original intent was to have each engine independent so that if one went out it would not affect the others. I had no idea they were so susceptible to small changes in fuel pressure. During construction I wasn’t convinced that one fuel line could feed four engines and it appears I was right. Each time the car went out it came back with one or more engines out. Then, if that one engine died, because all of the exhaust pressure lines were connected, the fuel pressure dropped and killed another. Despite these recurring problems, it did tap into the 50+mph mark, not great, not what I was hoping for but it was running, steering straight and stopping well.

That night I hooked up a second tank and ran the right and left pairs separately. I also changed the transmitter and receiver packs to 2000mAh AA’s to be sure I’d always have power. The gyro seemed to drain the small standard receiver back pretty quickly. The next morning(12/15/07), I was at my ‘official’ test site with the second tank and again had cold temperatures and balky engines. Once they were all running and as warm as they were going to get, I set it down and drove off. Part of today’s test was the radio range and it was stellar. I could drive it several hundred feet away and still have instant control. The car did a couple slow 40mph runs and it came back into the pits with all four engines still running!!!!! Top up the tanks and off we went for a speed run. Because this strip was longer than last night’s course the front engines sucked up all the fuel and shut down the rear two. If it ran hard long enough it would come back to the pits with only one running.

Again, it was a problem filled day as "Problem Child" lived up to its name. It ran into the 60+ mph range, usually on two engines, so there was some improvement. The next plan was to install a tank for each engine which should solve the fuel starvation problem and help tune the engines. I also had to replace one of the nylon gears...something got caught between the pan and the gear, and squared off the teeth. The one-way bearing in that same two-speed wasn’t grabbing consistently so had to be changed too. I designed the car to be as easy to repair as I could but it’s still time consuming. All in all, these were very minor problems but still a bit frustrating. I want to go faster!!!!!!

In order to mount four NTC3 tanks up front I had to add a little plate to extend the pan but since I’m going to re-cut it out of CF it doesn’t matter if it doesn’t look that great, as long as it does the job. The tanks ended up being mounted with the pickups at the front and although this isn’t the best place, for testing purposes it would work. The eight hoses necessary to run the engines would seem to be cluttering, but actually they were neater and less problem prone than the two lines and a bunch of T’s that I started with. When it comes time to build the body for this beast these NTC3 tanks will be replaced by some ‘bullet’ tanks by Sullivan. They’re a bit long but their length will allow a more sloping nose than the present variety.

Test date, 12/31/07. I was ready to go fast!!!! A half hour before heading out I checked to make sure everything was in the GO! position. I started all four engines with hotter plugs and made sure all the batteries were charged up. I got to the site and set up. Hoping to make sure that the day would be successful I tried to start #3......the starter box wasn’t working! I had replaced one of the motors with an old race motor and apparently should have replaced both. (20-20 hind sight!) Some fiddling with the old motor got it running but not strongly. Try to start #3 again.....something was hanging up in the drive train. An inspection revealed the clutch was engaged. The engine was removed, the errant clutch spring re-installed and the engine remounted. Try to start #3 yet again.....everything is spinning, nothing’s happening. Move to the other engines.....finally one starts, another stops at TDC every time. The starter won’t get past it to start. Finally I get a second engine to start and set it down but they promptly stall. Put the car in the trunk before I run it over!!!!!!!!

When I got home I tore everything apart, finding the bad plugs and another chewed up gear. The scary thing was that if I had gotten all of the engines running and tried to get some speed, I would have surely damaged the car since the brake servo, although it appeared to be plugged in, wasn’t working. Maybe someone was trying to save me from myself. I can’t figure out what was wrong with the plugs although I did switch the polarity on the igniter....I’ll have to check that out before running again.

Well, the post mortem investigation was quite revealing. The gel cell in the starter was apparently dragging down the power available to the starter motors so I removed it and rewired the motors in 12 ga. wire and replaced the 16 ga. with 10 ga from the power supply. I also replaced the cheaper original motor with another old race motor so they spin much faster now and with more power.

The glow plugs fell victim to a wayward 12 volt supply which went from a the power supply to one of the starter motor’s cases to the bolts mounting the roll cage to the igniter. I heard a pop once when I attached the igniter, similar to my last foray into bad voltage. The new wiring will prevent that from happening again. Once the starter was rewired and new plugs installed the engines fired right up.

One problem I haven’t been able to solve is getting the engines all in tune. They came from the box very rich and I have slowly leaned them out but they’re not getting much leaner. Reading the instructions gave me a ‘5 turns from bottom’ starting point and I was still a long way from that. I believe that the only way to get them all in tune is to do each one separately so I’m going to remove all but one engine and get it running good, then switch in another, working my way through the bunch. I believe that the car will be light enough for a single engine to pull it with the cage and other engines removed. Then once they’re all running well, re-install them and the roll cage and try for a speed run. Other wise it’s a hit and miss sorta deal.

I’m also chewing up some gears. I think the power of the engines is allowing the gear lash to get too wide so I’ll have to close that up, maybe even a bit tighter than normal. If the weather clears I might try for some tuning runs this weekend but it’s supposed to rain.

A week later it continues to be rainy and cold.....While the weather was uncooperative I decided to make things easier to work on. I ran yellow fuel and exhaust lines but with four per side it was often difficult to trace which line went where so I changed the exhaust lines to blue. I was also running into trouble when removing or installing the engine plate bolts since the interior ones were very difficult to get to. I trimmed some T nuts down and put them in the interior plate slots and changed the exterior nuts to wing nuts so they can now all be tightened or loosened from the bottom of the car without a socket or wrench.

It’s still raining.....=-( I’m hoping that by Saturday (tomorrow) it’ll be clear enough to do some tuning.
The weather cleared and I was at my test site by 10 AM. The road was still pretty damp but I was anxious to get going. I set everything up and got the engine started and warmed up. I set the car down and began making some easy passes to get the engine to temperature. I had turned the needles all the way in and then 5 turns out to approximate the correct mixture. It was still a little cool on this engine (right rear) so turned it in a quarter at a time until the temp was at 220.
The engine ran good but wasn’t able to rev. I adjusted everything I could but it still seemed to be starving for fuel. I’ll put a larger diameter fuel line on it and try it again but it may be a carb problem and will switch it with another as a different test.

I changed over to the right front engine and tuned that one in. It ran great and had plenty of revs but the one way bearing was slipping and the engine would rev without pulling. The gyro was acting weird so I unplugged it (I thought) but instead unplugged the brake servo so when I went down the road and went to turn around the car was moving too fast to turn and smacked the curb, shattering the four fuel tanks!

I was unhappy about the crash but the car had hit 65 mph on one engine so the day wasn’t a total write off. I went home and removed the remains of the four tanks and fabbed up a mount for the bullet tanks I would ultimately be using. I also picked up a new one way bearing and installed it in the front two-speed.

Sunday was sunny so I headed back out with a bigger fuel line for the rear engine as an experiment. The car started right up and I took a couple easy passes and the one way worked great. I came in to refuel and set the car down pulling away at partial throttle. At about 20 feet away it was obvious to me that I had no control over the car and could only watch as it moved away to some surely tragic destiny. It slowly arced left and then rubbed along the curb at about 20 mph until it ran into the side of a storm drain inlet and was catapulted out into the street. I jumped into my car and drove down, sure everything was broken.

It was surprisingly intact, only the front tank extension plate broken. It appeared that the receiver wasn’t working but I had mounted all of the electronics on flexible plates to avoid damage in just those situations like the previous day’s crash. The culprit turned out to be the on/off switch which chose to fail in the ‘on’ position. When the switch is bypassed, everything comes to life. Whew! I was afraid that I’d get it home and everything would suddenly work fine, causing me to not be at all confident that the problem was solved.