Help

[Craig]

I used my rc lab 7.7 club today for the first time. I was running on prima felt indoors. I have a few questions.

1. A rough set up (camber,oils and springs)
2.How tight should the belts been run?
3.A rough gearing point? I am completly lost at the moment.

Also i melted the front diff and i cant understand why could it be because the diff was either to tight or to dry?

[Bish]

Your best bet is to give Mike Smith at ModelTech a call on Monday.

He is always very helpful.

[James_Stewart]

Hi Craig,

1) I've emailed you my base setup, although you can't go far wrong with the kit setup either.

2) Run the belts so that they clear the cells and they don't skip. If you've got them so tight that you can play tunes on them then loosen the tensioner a bit.

3) For gearing we need to know what motor you're running, and you need to give us a rough idea of the size of the track.

Melting Diffs? I'd say they were too loose rather than too tight. What part did you melt exactly?

[Craig]

running a p2k on a fairly flowing track with about 15-17 second laps.

I melted the actual pulleys. Cant see the diffs being to lose dont really know i have never had any problems with diffs and my dad (tech guy) has built them all for long enough. One question should the diff balls "pop" in to the diff pulleys or should they be able to fall through?

Thanks for the set up ill try it on sunday.

[B3buggy]

were they the B type diffs?
i had to use 1/8th balls in mine so the diff worked properly, the little lip on the pulley surrounding the balls ment the diff actually ran on the pulley rather than the ball.(mike will correct me if i am wrong ;)) but this is how i understood it. see the rclab website for the alert on the issue.

ross

[Craig]

That is what i think had happened it hadnt ran on the balls but the pulley.

[B3buggy]

Yep that sounds like it. Talk to mike to find out more, but for a quick fix I carefully cut away the offending lip so the pulley hole area was completly flat, but this gave a lttle pulley wobble. The best way is to use 1/8th diff balls, they need no modification at all.
Is this using the 15/32 or 17/37 internal ratio?
On minipins, at WMCC i ran a matrix v10R using 120/38, will tell more when i see my friend tommorrow as he now uses my car inside and i really didnt run the car that often inside. more of an outside car.

ross

[Craig]

ill phone mike on monday. For a quick fix i will be using yokomo 33t pulleys they fit and i like the yokomo diffs.
Im using the 33/15 combo.

[James_Stewart]

I can't say that i've heard of the wrong size of diff ball being supplied, although there has been an issue with some inferior grade diff balls making their way into a few kits I believe, but this should only resullt in a gritty diff action.

In fact, i've just put a 32T pulley from a type B diff on some outdrives with the plates fitted, but with no balls in the pulley. The boss on one end of the outdrive provides enough spacing that the pulley still rotates freely, so I can't see how that could be the problem.

[B3buggy]

believe i had the problem only with the 37 pulley, but as i never ran with the kit optoion i dont know.
It isnt the wrong size diff balls, just they arent big enough to touch the plates. so 1/8ths are used to that they do, think mike found out about this after they were produced.

extract form rclab site, on the updates page about the b type diff.

''PLEASE NOTE: as these new diffs use 3mm diff balls, the use of the 37t pulley with them requires 1/8" diff balls. The internal diff parts are also different between the type 'A' and Type 'B' style differentials. The new Type 'B' diff uses 3mm diff balls with keyed diff rings and a spring loaded thrust bearing. Also note that the 37T pulley should be reversed when fitted to maintain correct belt alignment.''

ross

[James_Stewart]

The type B diffs come with 1/8" diff balls as standard, using a 32T diff pulley and a 15T layshaft pulley.

The old diffs used 3mm balls, and ran 15/32 as standard with 17/37 as an option.

If you want to use the 17/37 option with the type B diffs then you need to use 1/8" balls in the pulleys.