Whilst everyone is off playing with piston sizes, I thought I'd ask about drive shaft angle as a method of gaining forward traction in 2wds.

Something I can't get my head around is why adding more bind/friction to a drive shaft increases traction (apparently). I've seen several references to people shimming rear hubs forward and also raising the differential height to get more bind into the shafts.

In reference to raising the diff height, the Cougar manual actually states "the added friction can help make the car more stable on landing when under power. This setting could also help with traction on loose surfaces"

How does increasing the friction (and I presume wear) on the the shafts and out drives increase traction? On a stock powered car, I want the drivetrain to be as free as possible, so adding friction to the shafts seems at odds to what I would normally want to achieve.

Thoughts?

Hideeho
Fred, how did you arrive at your oil weights? percentage, drop test, field test or combination?

Adding more "bind" is similar to adding anti-squat. The suspension doesn't compress as easily on-power and so that force goes directly to the tires and isn't lost in the suspension.
As for rear hubs forward, that has more to do with putting more of the car's weight on the rear tires than increasing the bind in the drive shaft.

I used the very scientific method of just randomly picking one. Much like springs I just needed a place to start. I chose 30W in the rear since it seemed to work well with that piston in the past. Then I chose the front weight based solely on the drop test as with the springs. I only wanted to find balance. In my case, on my car with my pistons and shock locations, it was 20W front/30W rear. I only use 1 brand of shock oil. I like Associated shock oils. They have lots of choices.

This was my starting point. Driving the car to see how it handles determines if the oil weight needs to be adjusted as well as piston sizes. As with springs, if I change one end I change the other to balance.

I am personally not a fan of the driveshaft "bind" theory. I'm not saying there isn't merit to it. I just prefer everything be as free moving as possible. To me a driveshaft should rotate the drive wheels and that's it. I'd rather fix handling and traction issues elsewhere.

Hideeho
I just thought of another question. When you measure shock travel (not wheel travel) do you measure it on the buggy or off (I am assuming there will be a difference)? Also on the shock travel, do you limit up travel to match that as well as droop?

I think if this works it is going to end up costing me some money. If the basic concept works I imagine it will work even better with similar length shocks on end. With the B4.1 being relatively modular I will be able to use a T4.1 shock tower & front shocks. So I will end up buying more new shocks (just went to big bores), a new tower, as well as blank pistons to drill my own.

I had to go back and edit my piston size numbers that I posted the other day about my car. I got 2 cars confused in my head. The numbers changed but the logic and math stayed the same. This is why I write things down!

Mike Haynes used the double cadran driveshafts in all four corners on his sedan at IIC. The reduction in bind frees the car from the center off.

People on the TC6 thread went nuts when he let it out.

Hideeho
Once I thought about it, I think I have answered my own questions. travel is measured on the buggy, you do not match up travel. Using truck front shocks would only make the difference in travel (& therefore piston speed, difference in hole sizes & oil weight) smaller, but because geometry would still be different adjustments for that difference will still have to be made.

Hideeho
That fits right into the philosophy of fred. Each part has a function, let it do that function & don't try to make it do another. That's the whole purpose of balancing the springs being applied to a drive shaft.

I've seen some European companies making those for several offroad buggies & thought that was a very good idea.

I almost discount the effective change of the axle because I can't measure it. Except - you can hear the change in reduced chatter when you run them in the front.

Somebody stole my Venom hauler bag, and along with all my tools, I lost my collection of springs and my setup notes. Which means I lost my spring database. I'm not sure I'm going to do it again.

I set my shock down travel with internal spacers. I try to get the exact same amount of droop front to rear. I typically don't need much in the way of spacers on the outside of the shock to limit up travel. I typically just use a very thin one so the shock piston itself doesn't top out internally, if it even can. Whatever my total upward travel is, it's the same at both ends too. Knowing this I can then just measure the fully extended lengths of the shock shafts and then take these numbers and divide the longer number into the shorter one to get my percentage.

The reason I do it this way is so I can get the piston speeds matched front to rear per the same amount of wheel travel at each end. From there on you can go back and add or subtract spacers if you prefer more or less droop at each end but you need to know the initial number since it's speed isn't affected by total travel.

I wouldn't bother with truck front shocks. There's no need. No matter what you only need a certain amount of shock travel. Having a longer front shock that still is only used to the same extent as a shorter one just means you have lots of excess that you'll never use. You are also adding weight and it's added higher up so there are negatives to using them as well.

Great thread Fred, I'm going to give this a try. But I need some help, I'm trying to look for balance on my TLR 22, but I'm not sure. Do I have balance? See youtube clip below.

+ YouTube Video

Definetely subscribing!

[quote=micke_b;11320873]Great thread Fred, I'm going to give this a try. But I need some help, I'm trying to look for balance on my TLR 22, but I'm not sure. Do I have balance? See youtube clip below.

Slow your video down and watch if frame by frame. You are looking to see the rate at which the front and rear move back up after the initial drop. Any movement after that is not necessarily important. I've always taken video while holding down each end of the car and releasing simultaneously.

Thanks for the tips.

Made a new little video, I'd say this is balance? What do you guys think?

+ YouTube Video