[Help] on Boratko's AWD transmission

[Didumos69]

Hi,

In a push-along car that I'm building, I'm using Boratko's 5+R AWD gearbox and I'm running into problems when putting the gearbox into reverse.

I have an AWD setup with three differentials, the center differential is part of the AWD gearbox. The front and rear differentials each drive a 20 tooth double bevel gear which in turns drives a 12 tooth double bevel gear attached to the gearbox output axle. So the overall output-wheel ratio is 28:12.

I can push the car without problems in all forward gears, but when I put the gearbox into reverse, the 20 tooth double bevel gears and differentials start slipping. When I separate the gearbox from the rest of the car and drive it by hand, I can also feal much more resistance in reverse. In gears 1 to 5 everything feels very smooth.

As far as I understand, the different resistance between forward gears and reverse is mainly because of the fact that in reverse 5 of the 6 gears with clutch turn against their axles and in gears 1-5 only one gear with clutch turns against its axle.

Now my question is: Is this normal behaviour or am I doing something wrong? And what can I do to make the gears with clutch turn against their axles with less resistance?

And a separate question: Appearantly the transfer between the differential and the 20 tooth double bevel gear is the weakest point in my drive train. They are placed in a static transfer box and in a normal arrangement with the double bevel gear placed orthogonal to the differential. Still the differential can move quite a lot. So my question is: Is there a better way to transfer drive to the differential?

Hope someone can give me some directions.

Thanks!

Diederik

[__________________________]

Interesting looking gearbox.

[vibenpa]

the different resistance between forward gears and reverse is mainly because of the fact that in reverse 5 of the 6 gears with clutch turn against their axles and in gears 1-5 only one gear with clutch turns against its axle.

Edited March 8, 2016 by vibenpa

[Blakbird]

It should not be difficult to move in reverse. Reverse is a low gear so it will result in fast motor movement which comes with some extra friction, but it should be similar to 1st gear. Sounds like something is not right in your build.

[Meatman]

This is the same gearbox in the Vamp gt. I have built 2 of them. One uses the old 8 tooth style gear and the other uses the new style. The new style seems to work better than the old ones. One Vamp gt works smoothly in reverse and the other has a tad more friction. I also have that gearbox module on my desk at work and it works fine in all gears. You say at the front and rear differentials you are running a 20t bevel to a 12t bevel? Maybe try going with a 16t gear on the other end of the 20t bevel to another 16t gear so that it is 1:1.

[Didumos69]

It should not be difficult to move in reverse. Reverse is a low gear so it will result in fast motor movement which comes with some extra friction, but it should be similar to 1st gear. Sounds like something is not right in your build.

Okay thanks, I will re-examine or even rebuild the whole thing. I already had a problem with an axle being not straight which screwed the behaviour of the entire gearbox.

This is the same gearbox in the Vamp gt. I have built 2 of them. One uses the old 8 tooth style gear and the other uses the new style. The new style seems to work better than the old ones. One Vamp gt works smoothly in reverse and the other has a tad more friction. I also have that gearbox module on my desk at work and it works fine in all gears. You say at the front and rear differentials you are running a 20t bevel to a 12t bevel? Maybe try going with a 16t gear on the other end of the 20t bevel to another 16t gear so that it is 1:1.

What is the difference between old style and new style 8 tooth gear?

[zux]

What is the difference between old style and new style 8 tooth gear?

Old one:

New one:

[Didumos69]

Thanks! I did see that one, didn't know it was a replacement.

[Didumos69]

It should not be difficult to move in reverse. Reverse is a low gear so it will result in fast motor movement which comes with some extra friction, but it should be similar to 1st gear. Sounds like something is not right in your build.

I re-examined the whole thing. The problem was that not all gears with cluth had enough space to rotate freely. This actually troubled gears 1 to 5 too, but not as much as reverse, Once I made sure all gears could rotate freely, the gearbox perfomed as a I had hoped; perfect in all gears!

The only problem that remains is that after shifting gears several times, some of the gears with clutch again get closed in and slowed down by neighbouring gears on the same axle. This is probably because some of the gears I used - especially the grey 12 tooth double bevel gear - tend to slide along their axle quite easily, causing them to gradually move towards the gears with clutch when shifting gears. I replaced them with black ones, which in my case are more tight. Hope that will keep this probelm away.

Edited March 10, 2016 by Didumos69