Originally Posted by
djmachinist
I do have a question for the French racers: I am building the DXF car and a Motonica P8C, Both cars come with Gear type Diffs. When I last ran 2WD cars 15 years ago, Ball type diffs were prefered over Gear type diffs because of the ajustable tighness feature of the Ball diff. Back then when I tried a Gear diff, the car in a tight corner would lift the inside wheel off the track surface and all forward drive was lost momentarily. How do you set up the gear diff to fix this problem?
Dale Jones
In fact ball diff is a good solution for 2WD cars, but without suspensions the chassis is so rigid that it's very difficult to have a constant set up. For 5 minutes for example, the diff will be constant but for a 30 minutes use, in general we observe a degradation of slip on because of vibration and unscrew of the diff even if it has been set very hard at the beginning. So that, gear diff have been adopted. With gear diff, depending on the track you will drive, it's better and more constant. In general you have to consider to let your diff enough free and use a soft grease (but not silicon grease that is sticking) and to prevent too much forward drive lost, you play with the tyres shore to reduce this effect (between 37 and more shore for rear tyres & 48 and more shore for front tyres). But it's also a question of how you drive. But don't forget also that during the run grease will heat up and gear diff will be more free. Outside temperature will also play, I mean if you leave in a place where you have regurlarly around 80°F, your option should be to adapt a harder grease.
That's also the pleasure of these cars to find the good set-up, and believe me, when you have it, it's a real pleasure to drive.
As an information, we have had a race this year in France named the 24h of Chateauroux and it was better to have a gear diff of course...
Here are few links to watch videos about this event :
youtube.com/watch?v=wqvEUqHzJVs
youtube.com/watch?v=_SBgoQgGWjg
youtube.com/watch?v=6j_eHngMw0M
youtube.com/watch?v=4fLcLxs6c64
youtube.com/watch?v=EkXQh9J7LDg