Fangdango! V8 drag car

[paytonimusrex]

The body was finished last night. I dialed back the idea of doing a hex pattern on the roof and hood, as it turns out the metallic gold, despite seeming to be somewhat translucent did not really show much color change with the different backing colors. Not enough to warrant taking a chance any way. Otherwise, I think it came out pretty sweet, one of the first recent paint jobs I didn't mess up on.

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My new suspension links all came in, so that's my next move, getting them on, and getting the suspension adjusted/centered, etc. As soon as the new transmission plate arrives with the other updated parts, I'll work on that, the gas tank, hoses for cooling. Then I suppose I'll get back to the engine and fix the stuff I need to there and maybe fire it up.

that looks really good

 

[johnnydmd]

Unique color combo. Looks great!

It was supposed to be more yellow looking, to give it a "southwest" feel to match the name (Spanish party). It would have been much more yellow and bright with a silver or white backing, but I went with black. In the end I like how it came out a bit better, the gold with black parts/accents kinda gives me a 70's Trans Am vibe.

I got a lot of questions about performance/speed/gearing on social media, and I don't think I ever explained my thoughts here, so I'll repeat what I posted:

So, I want to explain why/how I am taking into account the rpm difference of this engine vs a nitro car.

I am using a 3 speed Kyosho Mad Force transmission. The Mad Force has a top speed (claimed) of 40mph. I own two of them, and using my gps unit was able to reach 38.7mph with the stock KE25 engine, which as a top rpm of 33k. I am also using the same rear diff from a Mad Force, so many things are the same here. This is where I had to start doing some math to figure out if the car and drivetrain were viable, and I did this long before making the final decision to move forward with the build.

The Mad Force transmission output is geared down 2.5:1 to the rear diff by a sprocket/chain/gear assembly. With this removed, and having no gear down, I have calculated that 11k rpm (Cison max rpm) would achieve approxiamately 33mph top speed. That's just math. Ok, so obviously, that's not too fast, and not fast enough to really be a viable race car at all.

There also was another problem. A max of 11k rpm would very likely barely be enough to get the clutch shoes to engage. This was what JohnnyQ90 ran into, and Dennis Dempsey. They solved their problems in different ways, with Johnny designing an entirely different, manual clutch, and Dennis going with light springs and adding emory paper inside his clutch bell, and reversing the shoes.

I have come up with a way to solve two things at once - top speed, as well as the clutch. By putting a large gear on the engine output shaft and having it hit a small gear on a seperate shaft the clutch bell sits on, I can spin the clutch at very nearly the same RPM as the nitro. This will not only give me the top speed I need, but it will spin the clutch fast enough to engage without resorting to modifying it.

With a 40 tooth gear on the engine, and a 20t gear on the clutch, I can in theory hit 66mph. With a 50t gear on the engine, I can hit 84mph. The way I've designed the system I can swap out a number of gears on each shaft to try the best combos. A lot will depend on how much low-end grunt the engine has, and how much the drivetrain can handle. It's all theory, but it's all been planned out from the start, and there have been various contingency plans made for any failure.

 

[TeknoJ]

So sick my dude.

 

[luke66]

yeahhh baby!

 

[AjDale]

Incredible!

 

[johnnydmd]

Busy, busy busy four-day weekend was spent mostly working on the car!

First I got my aircleaner and tach. As I figured, would have to make some room on the hood to fit it.

Overall I think 1/7th scale is just about perfect. Engine is way too small for 1/5th scale (though the power is plenty).

Since I was waiting on some CF pieces yet, I decided just to hook everything up and get my linkages set, all hoses and tubing run.

It was time to fire it up. Can't tell you how nervous I was. Initially I had a pair of NIMH 7.2v batteries. I simply refuse to have Lipo's in my house. Well that worked, though the starter motor was rated to 12v, but my starter button was melting. I went to Lowes and found a perfect 12v battery, and a much beefier starter button. I also noted that coolant was leaking badly in a couple of places, I won't go into too much details. One was me forgetting to tighten something, the other spots were defects and another couple of spots required clamps. Good news is the water pump has a LOT of power

The biggest problem though, was that the fuel was not passing in. I had gotten the engine to fire by dumping a little in the carb. I tried backing out the low speed (flow) needle, but nothing. I couldn't get the primer bulb to push anything through, there was definitely some blockage of some sort. Very quickly I saw that the carb came improperly assembled from the factory with the inlet block upside down, completely blocking the channel. Once that was corrected, I went back to trying to start.

More problem. The starter kept sliding and losing mesh. I tried a few things, then saw that I could put a bolt in a hole coming from the other side to act as a set screw of sorts. That worked.

Now with the fuel and starter issues sorted, it was time to fire it up and see how it would go. Nervous as hell. It fired quickly but would stall so I bumped the idle up some, as no doubt the thing was very tight yet. The first thing I noticed was, holy crap this thing was LOUD. I mean, LOUD, like a real V8 engine. A couple of times before I bumped the idle, I was starting it with the throttle open with my finger, probably too much and it just scared the crap out of me!

Below is the first video of it running extended, idling very high, and a couple of slight throttle blips. The tune is definitely rough yet, and I will take the idle down on the next time I start it and tweak the timing to get it right. Fuel mixture is probably a good bit off too after screwing around with the needles earlier, it's probably too lean to be sure.

The video sound doesn't do the thing justice at all - it's so much louder in person. Even with the crappy tune, I can tell though that the power output is probably pretty close to what is advertised. I initially thought the cam was 1/2 race, but it actually feels more like 3/4 race to me. I let it run a few minutes to check for any leaks, didn't see any, but there's a couple of connections I think will need clamps that don't have them yet. The thing can overheat quickly if the fan isn't running, so I was sure to keep that going after seeing some other guys overheat and spray coolant everywhere.

This week the rest of the chassis CF parts that had to get redone come in, so I'll have it all mounted correctly. I'll run the engine some more, tune it, tweak it, and I would expect in a week or so, be able to lightly test driving it.

 

[Xraycer]

Epic!

 

[332_RC]

Awesome!!!!!

 

[Doom!]

I'm glad you know what your doing, at the first problem I would have been lost. Way cool, When you get all the kinks worked out, this is going to be spectacular.

 

[CertifiedMike]

That motor is the coolest thing I don't own!!!
The video was AWESOME!!! You can hear the difference between that and a nitro for sure.
It sounds like its got some snap too!
If this car never makes it furter than here, its STILL the nastiest R/C I've ever seen!
That said... I can't wait to see the burn outs!!!

 

[paytonimusrex]

this is gets cooler everytime I see it

 

[johnnydmd]

Looks like JQ90 is using his Cison engine to make a 1/10th MT

It also looks like he's got a catastrophic coolant leak internally. I'm almost certain that it's the hose running under the intake manifold. Definitely needs clips, and it's also a reason to use an overflow tank with a vent to eliminate pressure.

Others mentioned sleeve rings, or head gasket, but turning the oil to a complete milkshake after a few minutes of running, nah, that's the hose. It did make me want to rush home after work to check my fluids! All good!

Oil looks crystal clear and clean, coolant is pink. Good to go!

However, given the nature of these engines, IMO it's probably good to change out the oil pretty much every time you use the thing. Probably same for coolant too. With that in mind, I'll put a 3 way valve on the bottom hose of the radiator to serve as an easy way to drain (identical to how my boat engine has it).

The rest of my CF parts came in. The transmission plate was spot on. I have it mostly finished, I do need to put the clutch/shoes in the bell, but so far everything fits like a glove. A very tight, tight glove. I also got the gas tank mounted, and the electronics now with the larger shelf. At some point I might wrap all of it up completely with something, heat shrink, not sure yet, just to keep it all clean from dust.

As it turns out my 3-inch dogbone WILL work, but I need to slightly adjust the upper link as it's slightly binding when the suspension is fully compressed. Just need to rock the upper link back 1-2mm and it'll be perfect. I'll also mount the brakes, which also have just enough room to work.

I need to replace the nitro fuel tubing with gas tubing. I wondered why my garage smelled like gas - it's from the gas evaporating through the porous hose material. Noticed my tank was getting lower each day, and a sniff test led right to the hose and primer bulb. Got a new primer bulb for a chainsaw on the way tomorrow. Better, low profile throttle servo comes today.

I've got a bunch of copper tubing I had from some other project to start fabbing up the exhaust pipes that will route out the side of the body.

After that, it'll be time to tune and break in the engine fully. I'm sure there will be some things to fix and tweak, but I'm just glad my fluids aren't mixing

 

[Finesavageboy2]

Carbon fiber...

 

[johnnydmd]

Carbon fiber...

I use a company to cut all mine mostly. I only do minor tweaks and stuff to it. I use a 3018 router to do any prototyping or emergency part work. No muss, no fuss

 

[Xraycer]

I use a company to cut all mine mostly. I only do minor tweaks and stuff to it. I use a 3018 router to do any prototyping or emergency part work. No muss, no fuss

What, you don't go old school and just use body sheers?!

 

[johnnydmd]

Ah, where did I leave off? I had a 5-day weekend, and all but one day has been spent working on this car, just put my nose down and grinded away with only some breaks for leaf collection in the yard. Maybe a little football watching too

The progress with both the engine and the car overall was a lot. There was also a moment of "oh crap" with the transmission. I will talk about that first.

While running the car, I noticed that the clutch was grabbing nicely (and realizing that the shoes are reversed, that was expected). Rather I should say, the clutch bell spins in reverse compared to a nitro engine because it's not bolted directly to the engine. What I saw, that made me sick and think how in the hell did I not realize this, was that the rear wheels weren't really turning. Doh! Clutch bell in reverse, TRANSMISSION in reverse!! I started thinking right away I had to solve this, or come up with some entirely new drive system. First instinct - disassemble the clutch bell and reorder the gears backwards, and flip the transmission around. Fail. Only the last gear has threads. The others are held on by that one.

Ok, so maybe I could somehow reverse the bearings and clutches in the trans and make it work. Nope. But - I did see that it might be possible to do it if I used just 1st and 3rd gears, making it a wide ratio 2-speed. A few minutes later, and I had it perfectly set up.

You can see I also hacked in my brakes. They work perfectly. I also see that it will be very easy to add a 2-step trans brake to this thing if I make a longer lever on the top and add a servo back on the suspension arch. That would be super useful for this engine and car.

Back to the engine. I replaced my fuel lines, and got the carb adjusted. I cleaned things up a lot and fixed some pretty decent flow issues that was causing it to run lean and very hot. Now I could get the idle down nice and the throttle response was vastly better.

I ran it quite a bit, tweaking the tune as much as possible. I noticed my oil was getting pretty cruddy looking. I decided to drain the oil and change it. I also checked the oil filter, and saw the magnet was covered with black metal sludge - doing its job, but I needed to put in some foam in the filter, I just couldn't figure out how. Finally figured that putting a bit of foam at the bottom where the pickup tube was would force oil through the foam and keep it cleaner. Meanwhile, this was my oil after an hour of break-in running:

Pretty disgusting. Probably a good bit of carbon from running ultra rich for a bit too. After the oil change, filter upgrade, I ran, and it seems to be staying clean. However, I think changing the oil and cleaning the filter after each use is probably mandatory.

I decided to take my valve covers and intake off and inspect the insides for any issues. First issue - one of my rocker arm adjusters came loose, so I had to re-tighten that one, and re-loctite it. All others were good, all lashes still good. Second issue - somehow during one of the numerous times I took the intake off and on, I got the gaskets upside down on one side, partially blocking the intake! Sure, glad I caught that. Even with those issues, this little engine was making serious power. I noted that I had no coolant mixing with oil, and no leakage in the engine that I could see. I put it all back together and ran some more, and it was even snappier and more responsive that the video above. I also noted that the rear wheels were spinning up really well, and the drive train sounded good.

I started making exhaust pipes, then stopped, I figure I'm going to just run open headers until I get the turbos on (probably my real "winter" project). I need to keep it simple for now, and quite frankly, seeing how fast this spools up right now, I need to see if the drivetrain can hold the power it's making now. Heck, I'm only running 93 octane gas at the moment. That will be changed soon.

I needed a way to shut the thing off, something better than just pulling the ignition battery connector off. Ordered a radio relay switch so I can shut it off remotely. Ran out of proper linkage wire too, so waiting on that to replace the coathanger wire I used for the brakes, lol. Now it was time to work on the stance some. I adjusted shock positions, and I think I got it right where it needs to be.

I fixed a few more minor coolant leaks (threads needed silicone) and let it sit. Today, my last day off, I'll work on rebuilding the rear end with heavy duty swing shafts and a locker spool. I also have some ultra beefy HPI gears that I'll put in too. It won't be long before I can start driving this thing around a bit to break it all in better and test. Then it'll be testing the launches.

My biggest remaining concern is the driveshaft. It's a heavy duty 8mm thing, but I do know that MIP makes some ultra beefy telescoping CVD's that would probably be better, as long as they make the brake end. I think they do, one of my local hobby shops has the shafts in stock, I might wander over to check it out.

I do have another set of gears for the engine output and clutch bell shaft. I'm currently using the 40/20t combo. I think I calculated that would give me around 65 mph top speed. I've also got a 50/16t combo, which would easily put it in the 80's. Not sure I need to do that.

 

[Doom!]

Glad you got some time to really go through it, finding glitches before they become problems is good.

 

[CertifiedMike]

If you need to go back to 3spd, you can swap your clutch/trans input gear set for a belt and pair of timing belt pulleys. Instant reverse!

That oil sure is dark! Nice to see no milk at all!!!

This gets better every post!

 

[paytonimusrex]

Ah, where did I leave off? I had a 5-day weekend, and all but one day has been spent working on this car, just put my nose down and grinded away with only some breaks for leaf collection in the yard. Maybe a little football watching too

The progress with both the engine and the car overall was a lot. There was also a moment of "oh crap" with the transmission. I will talk about that first.

While running the car, I noticed that the clutch was grabbing nicely (and realizing that the shoes are reversed, that was expected). Rather I should say, the clutch bell spins in reverse compared to a nitro engine because it's not bolted directly to the engine. What I saw, that made me sick and think how in the hell did I not realize this, was that the rear wheels weren't really turning. Doh! Clutch bell in reverse, TRANSMISSION in reverse!! I started thinking right away I had to solve this, or come up with some entirely new drive system. First instinct - disassemble the clutch bell and reorder the gears backwards, and flip the transmission around. Fail. Only the last gear has threads. The others are held on by that one.

Ok, so maybe I could somehow reverse the bearings and clutches in the trans and make it work. Nope. But - I did see that it might be possible to do it if I used just 1st and 3rd gears, making it a wide ratio 2-speed. A few minutes later, and I had it perfectly set up.

View attachment 208388

You can see I also hacked in my brakes. They work perfectly. I also see that it will be very easy to add a 2-step trans brake to this thing if I make a longer lever on the top and add a servo back on the suspension arch. That would be super useful for this engine and car.

Back to the engine. I replaced my fuel lines, and got the carb adjusted. I cleaned things up a lot and fixed some pretty decent flow issues that was causing it to run lean and very hot. Now I could get the idle down nice and the throttle response was vastly better.

I ran it quite a bit, tweaking the tune as much as possible. I noticed my oil was getting pretty cruddy looking. I decided to drain the oil and change it. I also checked the oil filter, and saw the magnet was covered with black metal sludge - doing its job, but I needed to put in some foam in the filter, I just couldn't figure out how. Finally figured that putting a bit of foam at the bottom where the pickup tube was would force oil through the foam and keep it cleaner. Meanwhile, this was my oil after an hour of break-in running:
View attachment 208389

Pretty disgusting. Probably a good bit of carbon from running ultra rich for a bit too. After the oil change, filter upgrade, I ran, and it seems to be staying clean. However, I think changing the oil and cleaning the filter after each use is probably mandatory.

I decided to take my valve covers and intake off and inspect the insides for any issues. First issue - one of my rocker arm adjusters came loose, so I had to re-tighten that one, and re-loctite it. All others were good, all lashes still good. Second issue - somehow during one of the numerous times I took the intake off and on, I got the gaskets upside down on one side, partially blocking the intake! Sure, glad I caught that. Even with those issues, this little engine was making serious power. I noted that I had no coolant mixing with oil, and no leakage in the engine that I could see. I put it all back together and ran some more, and it was even snappier and more responsive that the video above. I also noted that the rear wheels were spinning up really well, and the drive train sounded good.

View attachment 208390

I started making exhaust pipes, then stopped, I figure I'm going to just run open headers until I get the turbos on (probably my real "winter" project). I need to keep it simple for now, and quite frankly, seeing how fast this spools up right now, I need to see if the drivetrain can hold the power it's making now. Heck, I'm only running 93 octane gas at the moment. That will be changed soon.

I needed a way to shut the thing off, something better than just pulling the ignition battery connector off. Ordered a radio relay switch so I can shut it off remotely. Ran out of proper linkage wire too, so waiting on that to replace the coathanger wire I used for the brakes, lol. Now it was time to work on the stance some. I adjusted shock positions, and I think I got it right where it needs to be.

View attachment 208391
View attachment 208392
View attachment 208393

I fixed a few more minor coolant leaks (threads needed silicone) and let it sit. Today, my last day off, I'll work on rebuilding the rear end with heavy duty swing shafts and a locker spool. I also have some ultra beefy HPI gears that I'll put in too. It won't be long before I can start driving this thing around a bit to break it all in better and test. Then it'll be testing the launches.

My biggest remaining concern is the driveshaft. It's a heavy duty 8mm thing, but I do know that MIP makes some ultra beefy telescoping CVD's that would probably be better, as long as they make the brake end. I think they do, one of my local hobby shops has the shafts in stock, I might wander over to check it out.

I do have another set of gears for the engine output and clutch bell shaft. I'm currently using the 40/20t combo. I think I calculated that would give me around 65 mph top speed. I've also got a 50/16t combo, which would easily put it in the 80's. Not sure I need to do that.

i’m not gonna lie seeing this thread almost makes we wanna do something similar this thing is so sick, though I’d have no idea where to start and definitely don’t have the means to do it I can’t wait to see more, also did you say turbos???? you are adding turbos to this thing, this will be crazy

 

[johnnydmd]

Installed the trans brake. That was super easy with this setup.

My wife said "I thought this was a Winter project, what will you do now?". This always seems to happen, I plan a Winter project, and it gets done way ahead of time, lol. I told her "turbos"

So, the car is in a state where I should be able to start doing some light driving and testing. I could see me doing some work on the steering too. It's ok, as long as the travel isn't far. Turn radius isn't great with the settings I have, but that's ok I guess. I'm sure I'll brainstorm something, but I'm really limited in what I can change there. Mostly the thing just needs to only make small steering adjustments and stay straight. I noticed a tiny amount of bump steer too. Not happy about that, so I'll see what I can do possibly, but maybe it's ok.

Far from done though. I'm certain testing will reveal a lot of flaws and things that might need adjusting, or rethinking. I am, however, fairly confident the thing will be reasonably fast. There are doubters out there of course. Some question the power output of the engine (4.8 hp claimed by manufacturer). A similar sized V12 was tested at 1.24 hp on a "dyno", but the dyno setup was unconventional and did not appear accurate. It's a 48cc engine - and just from running it in person and seeing how much air it moved, how quickly it spools and how quickly it spun the rear wheels, I'm pretty sure this thing is probably somewhere near the claimed output. The thing literally sounds like a full-sized engine, it's that loud - video does it no justice at all. I ran it in my garage (it's a finished garage, sadly!) - with the side door open and not only did it make the garage stink like car fumes, it made the whole house smell (I got in trouble for that!).