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Old 12-28-2006, 11:15 AM   #1171
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We had a couple guys with servo troubles at our track this summer, but in both cases they failed to set the EPA. No matter what car you use, if you don't set the EPA, you will fry the servo. I have a lot of time on mine now with no issues, as do many other people at our track. The guys at our track who originally had issues haven't had any since they had everything set correctly. With the longer arm, your EPA will be really low... mine is around 29% I think. Keep in mind, that a longer arm is another performance gain that the 8ight offers. It will give more holding power just because of simple leverage. It also won't be affected as much by bumps and jarring since a 1mm flex/movement on a long arm is way less than a 1mm flex/movement on a short arm.
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Old 12-28-2006, 11:22 AM   #1172
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I agree with Hodge's

I found by cutting the vent hole in the Leaxn body, the throttle servo would run around 10 degrees cooler then without the vent holes. As well as my V-spec would run 15-20 degrees cooler too.


Turbo,

Like I said, the 559's are a great servo!! and there are 100's of them in 8ight's running strong across the US, but what I have seen is most of the time when one does fail, it usually has one in it...

Just make sure all the adjustments are correct (Epa etc. etc) and re-check them again after he run's it hard.
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Old 12-28-2006, 11:34 AM   #1173
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I agree about the EPA. Which goes back to my point 4 posts ago, which is to even out the brake bias so you're not over working the servo. The idea is to have enough stopping power with as little EPA as possible.
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Old 12-28-2006, 11:37 AM   #1174
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Quote:
Didnt you put some heat shield tape on your servo too? I may do that just in case as well... after I go through the linkage for a third time.
Yup, I had some double stick tape I use to mount componants in all my touring cars. It's made of some kind of foam, about 1/4 inch thick, and does a great job holding things down, while providing a bit of insulation. So far so good, knock on wood...

I thought about cutting that body vent open as well, but decided that since the most recent servo has lived without doing it, I'll leave it. The body does a fantastic job of keeping debris out. When I yank the body, it's always very clean in there, and I know an opening would invite crap into it.
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Old 12-28-2006, 01:11 PM   #1175
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if you dont want to open up the body at the front its worth doing so at the rear, a larger opening will still allow more hot air to escape without sacrificing protection at the front.

Cheers All and Happy New Year

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Old 12-28-2006, 01:28 PM   #1176
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My situation seems different from all the rest........


I know all my settings were correct, It seems my problem was simply do to not having the rubber grommets..... I run on a very hard packed indoor track (CRCRC) with huge jumps and all three of my servo's quit when I would bottom out after the biggest jump on the track, (no, the servo is not hitting the chassis) the same jump killed all three servos ..... so I do beleive my problem seems to be a little different from the rest..... They have since changed the track do to safety issues so with that and the rubber grommets I think I'm in good shape....
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Old 12-28-2006, 02:07 PM   #1177
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I don't know if having an offset servo arm is all that big of a deal...LOL...I usually just use the stock Airtronics arms and I always have them in uneven (offset) holes. It makes the linkages lay out and work better.

From a leverage standpoint, I think you'd be hard-pressed to make the case that there's enough twist on the servo arms from having more rear brake bias to smoke a servo. There are too many other parts in that chain flexing..you'd never get enough side-loading from the tip of that servo horn to make enough additional friction within the servo to cause any harm.

Oh yeah...I used the stock Airtronics bushings, with no spacers...we're going back out tonight with it again. It's got almost 2/3 gallon on it so far.
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Old 12-28-2006, 04:39 PM   #1178
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n/m

Last edited by ldawg; 12-28-2006 at 08:56 PM.
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Old 12-28-2006, 04:57 PM   #1179
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I get your argument, it just doesn't wash when you really think about it. The servo doesn't "see" which lever it's pulling on. Once it stalls, it stalls...front or rear. Weren't you talking about how the servo horn would twist the servo and load it sideways? If that wasn't you or I misstated your argument, I apologize.

At some point, without the EPA set properly, if you held the brakes full-on (stalled and still trying to go further) for some extended period of time, you'd probably end up burning out the motor, but that has nothing to do with front/rear brake bias.

That's what happened to Jerry's old JR servos. Turn off the radio and the throttle would go WOT...leave it that way for a while and it would smoke the motor. I think that you wouldn't have that problem with a properly set failsafe or a Spektrum.
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Old 12-28-2006, 05:38 PM   #1180
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n/m

Last edited by ldawg; 12-28-2006 at 08:56 PM.
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Old 12-28-2006, 07:52 PM   #1181
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Quote:
Originally Posted by ldawg
I see what you're saying, but my point is that if you distribute the load more evenly over the two rotors you will have more overall friction(stopping power) with the given throw. No?
I'm not too sure what you mean here, but...in a 1:1 car, the brake bias is generally 70-30 front-rear, because the rear can't actually contribute much in the way of energy dissipation ("stopping power"), due to weight transfer to the front during braking. Unless you have weight on the wheels, slowing them down only results in a tire skidding along, not slowing the vehicle.

Brakes in the rear are almost always smaller and the brakes are almost always driven by a smaller piston or run through a proportioning valve to dampen their effect.

That said, the Losi brake setup is pretty cool. The setup allows you to essentially set the brake bias even in a leverage/mechanical sense and the f/r bias is built in to the rotors.

Can you get more braking by dialing in more rear brakes? Sure...but I'm not sure why you'd want that. Would it take some greater force to have a 50-50 bias with smaller rotors? Yep. It would probably be easier to just take some out of the front by moving/shortening the front lever.
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Old 12-28-2006, 07:52 PM   #1182
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what's losi's take on all this.....have they weighed in on just what might be the cause...or a cure?
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Old 12-28-2006, 08:09 PM   #1183
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..

Last edited by ldawg; 11-15-2007 at 12:32 PM.
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Old 12-28-2006, 09:25 PM   #1184
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So far so good. 2 Tanks on the street and 6-8 tonight at the track on the same servo. Grommets and EPA. I also cut my throttle spring 1/8".

What battery packs are you guys running. After adding a JR8611a steering servo my factory pack drains too quickly.
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Old 12-28-2006, 09:25 PM   #1185
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It wouldn't be too hard to just use a larger rotor if that's what you were looking for. I'm sure there's room in there for something larger. Maybe not a full-sized (front) one, but something larger...it wouldn't take much.

I would venture a guess that's not the problem, though. I'm almost 100% positive that all the guys who have killed multiple servos in the RTRs aren't trying to go 40/60 f/r bias.

Last edited by Turbo Joe; 12-29-2006 at 12:58 PM.
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