fyrstormer

iTrader: (1)

Yeah, that's an older design. The notch in the pullstart spindle has been replaced by a ramp, and there's a spring-loaded pin sticking out of the crankshaft journal. The spring-loaded pin drops into the ramp on the pullstart spindle, so the pullstart spindle can grab the crankshaft and start it spinning. Once the engine is running, the pullstart spindle comes to a stop, and the spring-loaded pin sticking out of the crankshaft journal ratchets over the ramp in the pullstart spindle.

Here, I finally found a picture of what I'm talking about:



- - -

Anyway, I know there are better engines, but this engine is already ridiculously overpowered for the RS4 chassis. Imagine putting a Chevy big-block in a real 1990 BMW M3; that's what it's like. It doesn't need anywhere near its hypothetical peak power to hit top speed.

fyrstormer

iTrader: (1)

*sigh* I did not say there isn't an OWB in my engine. I said there is ALSO a racheting mechanism that allows the pullstart spindle to come to a stop while the engine is running, reducing the wear on the OWB and reducing the drag on the engine. In that respect it is superior to most pullstart designs.

Yeah, I read some more about them and they look like really nice clutches. Unfortunately the R40 Centax clutch bell uses a 12mm ID for the first gear and a 16mm ID for the second gear, and I can't find a 22t x 16mm Mod1 gear to use with the HPI Centax clutch bell.

I prefer pullstarts because they are self-contained. I know that a completely sealed engine that uses a starter box has better performance, but I'm not racing, and the stock engine is more than powerful enough, so who cares about making things more complicated just to get extra performance I won't be able to enjoy?

Christ, can't you people just admire my work without telling me all the ways I fucked up? I built this vehicle to meet my requirements, not yours.

BOOCAKE4U

I hear ya. Saw your thread here and URC and love the car. I'm an 8th scale guy but have always dug that E30 shell and want one just to have it. Anyway, great pics and great write-up and thanks for sharing it. Paint up another E30 for the shelf and beat the hell out of the one on it now (Saw you had a little boo-boo). Enjoy!

fyrstormer

iTrader: (1)

Actually I'm contemplating picking up the new pre-detailed E30 body from the new electric RS4 platform that's coming out soon, and using that for bashing. It's too late for this body to be perfect again, but you're right, I can always detail another body for showing off, and never actually run that one. (I actually bought two of the E30 bodies at once, because I figure it will probably be discontinued before I have a chance to buy a spare in the future, just like everything else I like.)

fyrstormer

iTrader: (1)

I revisited the suspension and installed some springs from an old Team Associated spring kit. 17.0lbs/in. for the front and 14.5lbs/in. for the rear. I also moved the orange swaybar to the rear axle and put the stiffer green swaybar in the front. The car handles much better now. It also dropped the ground clearance to about 1/2" instead of 3/4", which as it turns out is still plenty of ground clearance for the pavement I have to drive on.

fyrstormer

iTrader: (1)

A couple small updates: An adjustable-leverage purple servo-saver from Max Speed Technology, which unfortunately doesn't come with a 24-spline adaptor to use with Hitec servos, so hopefully Hitec will update the rest of their servo line to 25-spline before I need to replace the stock servo; and a GPM aluminum fuel-tank lid which has a proper O-ring seal instead of the lame open-cell foam ring that the stock fuel tank lid had. Also, you can't see it in this picture, but I removed the fuel tank, degreased the fuel-feed nipple and hose, and fixed the hose in-place with a drop of CA glue, because the fuel-feed nipple doesn't have a barb to keep the hose in-place. It's actually kind of amazing the hose hadn't come off already.



So that takes care of about 95% of the leaking from the fuel tank, which was getting to be a serious problem because it was risking contamination of the brake disc with oil from the leaking fuel. I wish I'd noticed the GPM fuel-tank lid has an O-ring sooner, I would've just included that part in my initial build if I'd known.

Also, here are the Team Associated springs I ended up putting on my Turnigy/HPI/Associated frankenshocks:





You can also see that I replaced the stock plastic rear body post bracket with an aluminum one. The plastic bracket was just too flexible and let the body lean too much in corners.

Joe Kimble

iTrader: (19)

I really enjoyed going through this thread. Good job man!

fizzy

iTrader: (15)

Good job and well done I too enjoyed this thread- Enjoy

fyrstormer

iTrader: (1)

Thanks. Oh, and for reference, with the new springs the chassis no longer sits super-high like it did in the original pictures.

WheelNut

iTrader: (5)

RC Tech users are generally the most intense racers out there. We can get pretty worked up about things like ride height or body height being off by a millimeter. Just look at the wiring thread in electric touring: Fastidious.

Anyway it is obvious your car is built for bashing and it looks pretty good for that. I wouldn't recommend getting a centax clutch personally. They are awesome, but they are much more sensitive to setup and have a lot more moving parts. Keep things simple and cheap for bashing.

fyrstormer

iTrader: (1)

I figured, but they ought to be capable of adjusting their expectations and reactions based on context. Also, for the record, I can totally appreciate fastidious wiring.

It looks like I could fit the Centax clutch from the HB R10 onto my RS4, but I tend to agree with you; I'm not frustrated by the ham-fisted-ness of the simple centrifugal clutch on my RS4, it engages at an acceptable RPM, parts are readily available, I have a stockpile of spare clutch shoes that I like, and all I have to do to keep it working smoothly is clean the dust out once every few months.

As for the rest of the car, it is indeed good for bashing. I can run it at top speed across a poorly-maintained parking lot and it somehow doesn't destroy itself. I have to be a little careful in corners because of the relatively soft suspension, but that's a small price to pay.

- - -

So, I talked to the guys at my LHS for a few minutes, and I concluded that I was overcompensating for the 30% nitro that I run. I had shimmed the cylinder head up to 0.8mm from the stock 0.4mm, because that's what I had to do to the same engine to avoid overheating in my Bullet ST, but I didn't account for two things:

1) The RS4 weighs a lot less than the Bullet;
2) The RS4 gets a LOT more airflow than the Bullet.

The result of those is that I was barely getting the engine up to operating temperature even after multiple top-speed runs, a situation that I had initially assumed was just the inevitable result of having a 3cc engine in a 1:10 touring car. However, over time the difficulty with the engine choking-out when cold, combined with my suspicion about why I was able to lean-out the engine to the point of stalling on high-speed runs without it overheating, led me to eventually realize that I was seeing the symptoms of *over*-shimming the engine. I knew what under-shimming looked like -- having to enrich the fuel mixture to the point of choking just to keep it from overheating, and difficulty maintaining a stable idle when hot -- but it never occurred to me that over-shimming would produce the *exact* opposite symptoms.

So in short, I removed one of the shims, dropping the shim-stack to 0.6mm, and suddenly I discovered a bunch of extra acceleration, the idle became more reliable when the engine is cold, and the peak engine temperature is right around where it should be.

fyrstormer

iTrader: (1)

This car had a rough summer, while I was figuring out how to make it run the way I wanted it to. (read: "lots of crashing at high speed".) Now that it's winter and it's too cold to run an engine that's broken-in for warm weather, I needed to clean it up anyway and replace a few worn parts like the diff outdrives, so while I was at it I decided to replace the chassis plate because it got bent a few times during "beta testing".

Because this wasn't intended to be a rally car, the steering links banged into the chassis plate when the suspension was fully extended. I knew this was a problem for a while, but I didn't care until a couple months ago, when I finally decided to grind away some of the metal on the chassis plate to make room for the steering links to move freely under all conditions. Now that I'm replacing the chassis plate, I needed to grind some metal off the new chassis plate too. Behold the difference of 1) knowing exactly what needs to be done instead of going through trial-and-error, and 2) not having to work around a mostly-assembled car while operating a running power tool. (the new one is on the right.)

fyrstormer

iTrader: (1)

The rebuild is complete. The diff gears were fine, but the outdrives had visible wear, so they got replaced with heavy-duty outdrives. All of the bearings were replaced with Boca Yellow Seals. The steering turnbuckles were replaced with purple titanium, and the ball-cups and ball-studs were replaced with Tamiya parts because they're better-quality parts. The suspension pins were replaced with a discontinued stainless-steel pin kit, which includes a rear brace to keep the rear A-arms from bending the pins in a crash. The clutch needed one broken spring replaced. One of the CVD dogbones had a slight bend that needed straightening. And as mentioned previously, the chassis plate was bent and needed replacing as well, though interestingly when I tried to straighten the bent plate before I apparently *over*corrected it, because it was actually bowed upward in the middle. The primer-less "racing" fuel tank that I installed several months ago did a great job of stopping the fuel leaks that were making a disgusting mess of the chassis, and it has a built-in fuel filter too. The engine required no service whatsoever, it's even still using the same glowplug that I installed when I first bought the car. I really like O'Donnell glowplugs.

Picture of the titanium turnbuckles and the clearance cuts on the new chassis plate to keep the turnbuckles from scraping at full suspension droop:



Here's a view of the single-speed conversion from an angle I normally never get to see it from, because the fuel tank is in the way. The fixed-position engine mount that the T3.0 engine uses makes getting the right gear mesh super-easy, because all I have to do is make sure the pinion and spur tooth counts add up to 65, and then bolt the engine onto the chassis:



I didn't have a way to show before how much extra ride-height my rally-modded RS4 has compared to stock, but now that I have a stock kit built-up, I can show them next to each other. Keep in mind the stock kit has the shocks mounted in the taller of the two optional positions, so it could be even lower than shown here if I had a glass-smooth track to drive it on:



And here's a picture of the rally-modded RS4 at full droop. Some people might think it's ridiculous to have a touring car with so much suspension travel, but damn it handles rough pavement well. It can even go on grass a little bit.

Paper2

The body BMW M3 is very nice for this car

fyrstormer

iTrader: (1)

It sure is. It's one of my favorite touring car bodies.