Insane speed has its' drawbacks!

Namuna · Post by **Namuna** » Tue Sep 05, 2006 11:40 am

Yesterday (Labor Day) turned out to be a really nice day out. My friend came over with his RC18T and I had my M18, we went to the tennis courts in my complex for some bashing sessions.

...I brought my 3cell lipo pack and I had previously set the Mamba ESC for all super-aggressive settings so I can get max run out of my 6800.

We caught a break! the tennis court area became available (3 courts, side-by-side). Perfect opportunity to really open-up my M18 (with the 3cell Lipo pack)!!

Well, my speedlust has cost me!

- Even running 42t/17t spur/pinion, the length of 3 tennis courts (side-by-side, not lengthwise) still isn't enough to fully realize the top end potential of the 6800 with the 3cell lipo (man! that 8000 must be an absolute MONSTER!). By the time it's close to full speed I already have to slow it down (and by slow it down I mean STOMP THE BRAKES full force!)
- After a couple of high speed runs, the motor mount came loose and I lost 1 of the screws. I got lucky and found it and had to use threadlock to keep the screws from coming loose again.
- Since the Lipo packs aren't a direct fit in the battery bay area, I've been using velcro to hold it in. Running at the "regular" speeds, this method is perfectly fine. But running at high speeds, with all the jarring acceleration and braking the battery ends up coming loose and smacking against the steering rod.

- I'm running the Futaba S3102 Servo with Xray Servo Saver and medium foams in the front. At high speeds, trying to make hard turns results in way understeer (which results in some HARD HARD HARD!!! fence ramming

). Either the Servo doesn't have enough torque to pull the wheels around, or it does have enough torque but the servo saver is engaging (from such high forces on the steering) and causing the understeer.
- I'm glad I bought extra foams, all the hard starts and stops really puts a LOT of wear on the foams!
- The Spur gear is composite, but I'm running an alloy pinion. The pinion came loose on one of the high speed runs. A minor issue to fix, but it would've sucked hard if it threw the pinion and got lost.

Amazingly, enough after a few near-faint-inducing fence crashes (one of which was hard enough to wedge the car about 7 inches underneath the fence link), no serious damage was done to the car (I can't say the same about my shit marinaded undies though).

I've learned my lesson; The 3cell pack will now be sitting in the toolbox only to see the light of day when there's PLENTY of space AND a whole lot of padding in the run area. For all other occassions the 2cell Lipo and 6cell NiMH are actually a good deal more than adequate to get the job done!

Murdoch · Post by **Murdoch** » Tue Sep 05, 2006 1:38 pm

Sounds like you had a hell of a time man. I have a little over three days til my M18 is ready to tear around the blacktop.

I live in a town where one day a week an actual street is clear for three blocks. So it would make a perfect place to do speedruns.

Namuna · Post by **Namuna** » Tue Sep 05, 2006 2:33 pm

You lucky BASTARD!!

I hope that street surface is decently smooth man, or that you've got lots of soft grass on the shoulder...Otherwise things could get ugly QUICK.

Hehe, now that I think of it...I've got the Spektrum DX3. If I can find a long stretch of smooth road, I could rig up a parachute in the back of the car and use that usually unused 3rd channel to trigger the chute for fast stops.

That would be some funny shit to see!

Murdoch · Post by **Murdoch** » Tue Sep 05, 2006 3:14 pm

Or rig up a retro rocket brake.

Clint · Post by **Clint** » Wed Sep 06, 2006 12:23 pm

Here's the control rod style servo saver i was talking about the other night. Its more stable at higher speeds than the stock xray saver.

the brass peice floats the servo horn between the stiff springs on the control rod. The difference in spring length matters not. all you really
need is the half inch of spring on each side...but then it needs another
steel collet to hold the other spring down. the collet would hit the center stabilizer bar, so i used a longer spring instead.

Namuna · Post by **Namuna** » Wed Sep 06, 2006 12:44 pm

Damn! So you're using a big-assed spring as the control rod. Ingenius!

It seems like another plus to using that setup is the ease of recentering the Servo too! Instead of having to reposition the horn while the electronics are on...You'd just loosen the collet and shift the control rod a little. Nice!

SuperFly · Post by **SuperFly** » Wed Sep 06, 2006 1:34 pm

So Clint, when are you going to show us your improved Space Shuttle design?

betty.k · Post by **betty.k** » Thu Sep 07, 2006 2:30 am

Namuna wrote:Damn! So you're using a big-assed spring as the control rod. Ingenius!

actually it looks like a solid rod that the brass part is able to move along, it's the springs over the rod holding the brass part in place.

i could be wrong though....

payaso · Post by **payaso** » Thu Sep 07, 2006 3:13 am

betty.k wrote:
Namuna wrote:Damn! So you're using a big-assed spring as the control rod. Ingenius!
actually it looks like a solid rod that the brass part is able to move along, it's the springs over the rod holding the brass part in place.

i could be wrong though....

Nope, you be right. At least that's the way I saw it.

silla

Murdoch · Post by **Murdoch** » Mon Sep 18, 2006 11:21 pm

Where would you get parts like that from?

because I just finished my build today and took it for a rip. The servo kept stalling, so I tore it apart and found out the comms were shit. So I broke it in like a regular motor and it seems to have improved. Might have taken some life out of it though.

Just running on the street is just tearing up the foams like nobody's business. I need to get some hard rubbers for it.

Murdoch · Post by **Murdoch** » Fri Sep 22, 2006 9:27 pm

well. no one had the rubbers I needed, so instead I picked up some medium foams. Worked awesome for running around in the parking lot. Even at high speeds, I can blip the throttle and break the rear end out for some nice powerslides.

that is, until the car slammed into the sidewalk.

Chassis is okay. so is the rx, ESC and motor. but what i'm worried about is the battery.

dogbreathracing · Post by **dogbreathracing** » Thu Nov 13, 2008 8:10 am

High speed is cool
Been doing some myself...

[YouTube]http://www.youtube.com/watch?v=NtU4N4_wIGA[/YouTube]