Fangdango! V8 drag car

[DavidB1126]

Rc build of infinity you mean

 

[johnnydmd]

Been working on two things while waiting for a nice enough day to test and tune.

First, I really wanted to fix the steering properly. I was looking at my original design sheet and realized that my original plan was to have the steering servo flipped around from how I had it now. I decided to take the front end apart and see if that was feasible, and sure enough, not only was it, but it made much more sense and things lined up just about perfectly. I just needed to redesign the mount, cut a prototype with my router, and test.

The main change was that now I could use straight links. I do need to replace the servo horn with one that has the mounts horizontal instead of vertical so that both links can mount on the top (like the red one on the right) to remove any bump steer. The red one was at the perfect level with zero bump steer.

I could in fact even offset the servo so that the links are the same length, but this thing is nestled pretty tightly near the radiator, and I don't believe there is enough room to get it perfectly centered, so I'll probably just leave it alone.

This weekend I'm working on the brake mechanism. I had used a hacked-up piece from a Mad Crusher but have always had the intention of re-creating it with CF and aluminum tubing. I've got the hard part started, which was getting the piston hole drilled out in the very hard tubing (need to get some better cutting bits for that if I make more of these, that was a serious PITA). The rest is not easy either though, initial attempt I'm going to cut the CF by hand.

One other thing I'm looking at is doing something different with the throttle servo mount, maybe moving it in closer to the engine.

 

[WickedFog]

Been working on two things while waiting for a nice enough day to test and tune.

First, I really wanted to fix the steering properly. I was looking at my original design sheet and realized that my original plan was to have the steering servo flipped around from how I had it now. I decided to take the front end apart and see if that was feasible, and sure enough, not only was it, but it made much more sense and things lined up just about perfectly. I just needed to redesign the mount, cut a prototype with my router, and test.

View attachment 212024

The main change was that now I could use straight links. I do need to replace the servo horn with one that has the mounts horizontal instead of vertical so that both links can mount on the top (like the red one on the right) to remove any bump steer. The red one was at the perfect level with zero bump steer.
View attachment 212025

I could in fact even offset the servo so that the links are the same length, but this thing is nestled pretty tightly near the radiator, and I don't believe there is enough room to get it perfectly centered, so I'll probably just leave it alone.

This weekend I'm working on the brake mechanism. I had used a hacked-up piece from a Mad Crusher but have always had the intention of re-creating it with CF and aluminum tubing. I've got the hard part started, which was getting the piston hole drilled out in the very hard tubing (need to get some better cutting bits for that if I make more of these, that was a serious PITA). The rest is not easy either though, initial attempt I'm going to cut the CF by hand.

One other thing I'm looking at is doing something different with the throttle servo mount, maybe moving it in closer to the engine.

Could you use a rack and pinion for the steering? The pinion could have an arm on it for the servo to actuate. Just make the pinion big enough so it matches the horn's throw. Much better than stardard RC sterring links anyway since the horn travels on an arc, which changes the link angle. This would get rid of uneven bump steer. Come on man. You got the baddest RC drag car on the freakin planet! It looks like a shrunken 1:1. You might as well go the extra step

Or we'll forever call you 'Short Link Larry'

 

[johnnydmd]

With a few days of being home for the holidays, and no work, Johnny was all play

I finally got around to replacing the hacked Mad Force brake setup with a fabbed one using the disc, calipers, and piston. I had a hell of a time drilling out the holes in the alloy tube - in hindsight I should have made it from plastic it would have been vastly easier. Also having a better drill press would have been key if sticking with the alloy.

Little rough looking, but the piston fit fine, and moved freely.

Put it all together, everything was very, very snug. Much of this car has ridiculously tight tolerances.

That right there is the heart of this project and concept. This is what will compensate for the RPM range vs a nitro or brushless car. Without a setup like this, these little 4-stroke engines are not useful for getting any real speed.

After I was done with that, I moved the throttle servo to a new spot that makes more sense.

I considered adding additional braces from the new servo mount to the rails, to minimize flex when braking, but probably don't need to.

Now the design seems pretty close to finished.

I might get some of the parts I have modded or cut with my router re-done, mainly the lower chassis plate since I've added quite a bit of stiffness in the design, but that's not something to high on my priority list.

I also got the new front servo arm so that I could get the steering right.

Got it all adjusted, it's rock solid now, with no bump steer, so, yay Ideally I would have had one link on the servo, and a long link across to simulate a rack/pinion setup, but alas, the limitation is the hubs' arm lengths not providing enough clearance past the shocks. But this is ok. It's a drag car going in a straight line, not a road racer.

For the most part it feels pretty solid and clean now. I haven't weighed the thing in a while, I'm guessing it's around 12 lbs. based on what I added (intentionally) after last weigh in at 10.9 lbs. All of the added weight was in the rear, so the balance is better (I can tell just by holding it in my hand).

Now, it's back to the engine!

Several things on that front for sure. I need to adjust the timing, its way retarded at this point. I have a timing gun, but will probably just do it by ear as I always did back in the day with my real V8's. Find the sweet spot Next, it's been made public that Cison is releasing a supercharger for the engine in February (meaning, it'll probably come out in April lol). Do I need it? Probably not. Am I going to get it? Hell yes! Much easier than the turbos, and way better for the engine (no excessive heat).

Also, Cison is coming out with copper head gaskets. Good. The paper ones are a known failure point (and not just on these engines, but real sized ones too). That's a definite reason for me to tear the engine down again and do some other things I want to do - like double check my oil scraper rings and make sure they are floating freely as that's something some people have had issues with (though that was in the first batch of engines). Some have had to lightly sand the bottom of the rings to free it up, but I think mine are probably ok, I didn't see any problems during assembly.

 

[Doom!]

You've been a busy boy! I am amazed how much tweaking and tinkering have gone into this build, the more amazing part is that it keeps getting better.

 

[Littlemotor]

I’m just utterly speeechless on this build… We all know how much of an accomplishment that is..

Absolutely killer job thus far man.. I don’t want it to end lol!

 

[johnnydmd]

We had some warm, though damp weather, but I did get to do some tuning and testing. First thing I noticed was I had flashover on at least two spark plugs, causing the engine to run roughly. This was mostly due to the boots not sitting properly on the plugs because of my fabbed clips. I took them off, went back to just a ball of wire in the boot, and that solved it. I spent a couple of hours then just messing with timing, and the carb mixture. Eventually I had the thing purring at a nice choppy idle of around 2200 rpms. I also discovered my fuel hose was not well seated on the gas tank, causing an air leak. Solved that. Throttle response was vastly better, and the engine would go from 2200 to 10000 with a quick throttle blip. That thing spools up insanely fast - much faster than a nitro engine.

So that was the good news. The bad news...I took the car for some testing hoping to get a nice video at least of the car driving around, not to mention maybe some launch tests. I was next to my truck, and gave it a little gas, and it spun out, turned the wheel to correct it and my wheels turned the opposite way due to me having the servo plugged in backwards, and it veered right into my truck tire, lol. The front bumper/radiator mount flexed enough that the overflow tank went right into the engine and paid the ultimate price.

Got home and decided that design really sucked anyway, way too constricted and lack of access to the servo was annoying. I had some spare Rustler nitro tanks, and made an overflow tank from one of those, and mounted it on the side. I also put in some petcocks to be able to block off flow when taking stuff apart too. I also changed up my throttle linkage a little.

This also allowed for me to have extra coolant. I was careful to put the pickup towards the rear of the car, so it wasn't sucking air when accelerating. Made a mount out of Lexan for now, I'll add that to the chassis design, and at some point, I'm going to replace the lower plate and the other prototype parts I cut myself anyway. Ran the car a bunch after that to test, and the car ran nice and cool, good coolant circulation.

The last issue I needed to deal with was that lately I'd been seeing some pretty excessive oil consumption on the right cylinder bank. This in the form of leaked oil out of the exhaust, plus smoke when gunning it. I also saw oil spraying out of the head (there's literally open screw holes on each end, which I think are for the "optional" oil routing. It wasn't a lot, but definitely annoying. Need to find out if I need to plug those holes or not. Might be needed for ventilation, since the valve cover doesn't have any. I made a dipstick using a large zip tie and noticed that my oil level was well up into the crank shaft. Definitely too much oil in the engine. So, I drained it all out, and this time instead of the recommended 28ml, put in 25ml. This would account for oil laying around in the engine, I hoped. Checked the dipstick, and it looked pretty good, maybe still slightly too much. Ran the engine and at first a little oil was still coming out of the exhaust, but it was far less than before, and no smoke. After a little running, it seemed like no oil at all really coming from the exhaust, and the oil flow looked smooth, no bubbles from the crank stirring it. Probably 24ml is the right amount at this point, but I'm using the dipstick to get it perfect.

One other thing is looking clear, and that is that I probably need to gear the car up some more, it's just ridiculously torquey. I have a set that would take it from 2.5:1 to 3:1.

 

[Doom!]

Sucks about the mishap, but turned out with a better end result so all is good.

 

[Littlemotor]

Sucks to hear about the accident, but finding design flaws is never a bad thing.. I’m sure it doesn’t sting any less just hearing that from the peanut gallery though.. Hopefully the thirst for oil has been handled too. Sound like it’s not nearly as bad, so likely you’re on to something.. This thing is such an awesome one to spectate… I REALLY wanna HEAR it…

 

[CertifiedMike]

We had some warm, though damp weather, but I did get to do some tuning and testing. First thing I noticed was I had flashover on at least two spark plugs, causing the engine to run roughly. This was mostly due to the boots not sitting properly on the plugs because of my fabbed clips. I took them off, went back to just a ball of wire in the boot, and that solved it. I spent a couple of hours then just messing with timing, and the carb mixture. Eventually I had the thing purring at a nice choppy idle of around 2200 rpms. I also discovered my fuel hose was not well seated on the gas tank, causing an air leak. Solved that. Throttle response was vastly better, and the engine would go from 2200 to 10000 with a quick throttle blip. That thing spools up insanely fast - much faster than a nitro engine.

So that was the good news. The bad news...I took the car for some testing hoping to get a nice video at least of the car driving around, not to mention maybe some launch tests. I was next to my truck, and gave it a little gas, and it spun out, turned the wheel to correct it and my wheels turned the opposite way due to me having the servo plugged in backwards, and it veered right into my truck tire, lol. The front bumper/radiator mount flexed enough that the overflow tank went right into the engine and paid the ultimate price.
View attachment 213206

Got home and decided that design really sucked anyway, way too constricted and lack of access to the servo was annoying. I had some spare Rustler nitro tanks, and made an overflow tank from one of those, and mounted it on the side. I also put in some petcocks to be able to block off flow when taking stuff apart too. I also changed up my throttle linkage a little.

View attachment 213207

This also allowed for me to have extra coolant. I was careful to put the pickup towards the rear of the car, so it wasn't sucking air when accelerating. Made a mount out of Lexan for now, I'll add that to the chassis design, and at some point, I'm going to replace the lower plate and the other prototype parts I cut myself anyway. Ran the car a bunch after that to test, and the car ran nice and cool, good coolant circulation.

The last issue I needed to deal with was that lately I'd been seeing some pretty excessive oil consumption on the right cylinder bank. This in the form of leaked oil out of the exhaust, plus smoke when gunning it. I also saw oil spraying out of the head (there's literally open screw holes on each end, which I think are for the "optional" oil routing. It wasn't a lot, but definitely annoying. Need to find out if I need to plug those holes or not. Might be needed for ventilation, since the valve cover doesn't have any. I made a dipstick using a large zip tie and noticed that my oil level was well up into the crank shaft. Definitely too much oil in the engine. So, I drained it all out, and this time instead of the recommended 28ml, put in 25ml. This would account for oil laying around in the engine, I hoped. Checked the dipstick, and it looked pretty good, maybe still slightly too much. Ran the engine and at first a little oil was still coming out of the exhaust, but it was far less than before, and no smoke. After a little running, it seemed like no oil at all really coming from the exhaust, and the oil flow looked smooth, no bubbles from the crank stirring it. Probably 24ml is the right amount at this point, but I'm using the dipstick to get it perfect.

One other thing is looking clear, and that is that I probably need to gear the car up some more, it's just ridiculously torquey. I have a set that would take it from 2.5:1 to 3:1.

Sounds like it needs a puke tank to catch that oil!

Are taller tires out of the question?
If everything else is dialed in but torque is still mega, I might try for more top speed if this is practical.

Now that the paint is broken in, no need to worry over the occasional drip or slip... at least thats done!

I agree... REALLY looking forward to some test and tune vids!

 

[johnnydmd]

Sounds like it needs a puke tank to catch that oil!

Are taller tires out of the question?
If everything else is dialed in but torque is still mega, I might try for more top speed if this is practical.

Now that the paint is broken in, no need to worry over the occasional drip or slip... at least thats done!

I agree... REALLY looking forward to some test and tune vids!

Haha, yeah, it definitely was shatting a bunch when I had too much in, but now it's not spitting any at all, so I think I'm good. Level seems to be holding in the sump too.

Taller tires are possible, but not much taller. I really had difficulty finding anything that would fit that was decently larger than the typical 1/8th scale drag tires. So with my gearing change, the top end should be a good bit higher. I did confirm that the engine easily gets to 10k rpm, so my math says my current gearing should be 60+ mph, but if I change to my other set, it'll be 80+. If anyone knows of any good 1/7th drag wheel/tire combos in 17mm hex, I'm all ears. Maybe I could have something custom made...I could really go for something about 10-15mm taller.

Oh, I didn't have the body on yet when I crashed, thank god! This was literally just me starting the engine and letting it warm up, setting it on the ground and giving it a little gas just to jog around a little. That body is still mint (for now!).

 

[CertifiedMike]

Haha, yeah, it definitely was shatting a bunch when I had too much in, but now it's not spitting any at all, so I think I'm good. Level seems to be holding in the sump too.

Taller tires are possible, but not much taller. I really had difficulty finding anything that would fit that was decently larger than the typical 1/8th scale drag tires. So with my gearing change, the top end should be a good bit higher. I did confirm that the engine easily gets to 10k rpm, so my math says my current gearing should be 60+ mph, but if I change to my other set, it'll be 80+. If anyone knows of any good 1/7th drag wheel/tire combos in 17mm hex, I'm all ears. Maybe I could have something custom made...I could really go for something about 10-15mm taller.

Oh, I didn't have the body on yet when I crashed, thank god! This was literally just me starting the engine and letting it warm up, setting it on the ground and giving it a little gas just to jog around a little. That body is still mint (for now!).

Lucky for the body!

Lucky for the rest that this was just a jog and not a WOT blip!

 

[johnnydmd]

This looks to be the final design sheet of the chassis. I've given the chassis a name - Torqnado.

Now I just have to do (a ton) of measurements of the links/braces since most of them are shimmed up and get proper length ones.

I'd like to get my hands on one of the new Toyan V8's eventually, or at least the motor mount so I can add the holes for that engine.

 

[WickedFog]

This looks to be the final design sheet of the chassis. I've given the chassis a name - Torqnado.
View attachment 213358
Now I just have to do (a ton) of measurements of the links/braces since most of them are shimmed up and get proper length ones.

I'd like to get my hands on one of the new Toyan V8's eventually, or at least the motor mount so I can add the holes for that engine.

You might be able to get Toyan to send you the motor mount hole spacing info.

 

[johnnydmd]

Whack weather, but I did manage to do some tuning. Got the idle down, nice and lumpy like I like it Timing advanced a bit, and it's got that real choppy lope when you idle up, and then super responsive when you gun it.

I'm almost positive I'm going to swap out the 2.5:1 gearing on the engine output to 3:1, just going by the wheel speed. I want to see a little more than I am, but I'll do that after some launch testing. That might have to wait quite a bit, apparently, we are about to go into a deep freeze for an extended period here we haven't seen since 1977 in Maryland. I know the engine would be ok, but traction would be awful.

I was hoping yesterday to get a chance as it was in the mid 40's, but the wind was insane. So, I decided to build a transport box instead.

Just gotta put in a few cross braces and the lid. Need a pair of rubber straps to hold the wheelie bar down in the stoppers. It looks heavy, but the case is made of light pine, so it's liftable by one person.

 

[Xraycer]

Looking forward to see you bling out that transport box!

 

[johnnydmd]

I will have a booth at Motorama Feb 15-16 in Harrisburg PA. This car, along with Invader II, and several others from our team will be on display at the booth, so if you're going be sure to stop by in the main hall!

 

[WickedFog]

Wish I could see them in person. Ship them to me and I will ship them back

 

[johnnydmd]

I've been contemplating a rear tire change for a while now. The Primes just seemed too small, and didn't fill out the wheel well that good.

They are 112mm tall. I had to also raise the rear suspension a notch, otherwise it could bottom out potentially. They were also barely bigger than the front Banditos which are 104mm tall.

When I first started designing this thing, my choice was ProLine Menace, but they seemed a little big at 141mm tall, and 80mm wide vs the 60mm Primes. I just kept on thinking I should try some. So, I finally grabbed a pair.

I was super impressed with them, but yeah, they did seem a bit huge. I managed to get them on the chassis, but had to move the shocks in as they rubbed. The car looked a little cartoonish. I slipped the body on, and man, it was close. So close. No cigar though. The body rubbed. A few mm's wider and it would have been good. (BTW, those tires and the extra offset RAID pieces are for sale, 65 plus shipping).

I really needed something about halfway between the Primes and Menace. I decided to try searching in a different way on Google and found something that was exactly the dimensions I was looking for (125mm tall, 70mm wide). My LHS had them in stock, so I snagged them right away.

The only thing is, they are not belted like the other tires - but they claim to not balloon so I figured it's worth a shot. The wheels aren't quite as pretty, but that's ok. I noted that the tire was rather thick, but a very soft, sticky compound, and really smelled like a new tire (Love that smell!). I bolted them up, and it was a tight fit on the chassis, but nothing rubbing. I was able to drop the suspension down a notch too without any bottom out potential.

Scale wise, much better in relation to the front tires too. So how did it look with the body on?

Well, that was just about perfect!

So essentially, the car is done until I can test and start playing with gearing, shift points, etc. I do have some new chassis pieces coming (100mm m3 standoffs in matching red) to replace the grey links I stole from one of my Mad Crushers. But that is all. I should probably weigh the thing (best guess is that it's at about 12.5 lbs). I think it's much better balanced now since the last time I weighed it. I also want to paint the mirrors gold like the body.

Maybe I mentioned it, I can't remember, but Cison Engines is dropping a supercharger for this V8 next month. I am certainly going to grab one! I am not sure the extra power is needed, but I cannot resist having a working blower sticking up out of there

 

[luke66]

You are 90% of the reason I need a nitro. So cool!