Hi All,

recently i decided to go for a RC Class 1 buggy, with looooong travel suspension, which is started very well, and than... a very well placed faceplant in the gorund of mechanics. Result some broken cardans, etc... After 5th or 6th rebuild of the drivetrain, i finally found one solution, which lasts at least for 1 meter. Another issue, that the solution works against the suspension. i added also some bars to make it more stable, it seems that the project will turn into a static display model, for pushing by hand it seems will be ok. I don't want to cover my feelings, it tastes bitter. Worst case scenario to build a solid axle, but than the point of the project is gone... Attached a picture, although the buggy itself lays in pieces... i rebuild it with new designs at least twice pro day.

I decided to turn to the community for help, maybe some of You are also itnterested for technical challenges.

Have You ever met, done such solution? https://www.flickr.com/photos/22510469@N06/5762688308/in/photostream/

I am a bit afraid, that Lego parts don't allow such design, since they can bend, twist due to the material and connections, especially with PF.

Opinions?

Thank You in advance!

agrof

Does it work? it looks a nice design.

H

I ve used something similar on my polaris rzr, check it out on my blog... It was a three links system tho, but it worked surprisingly well

I think the reason why your u-joints are breaking is because there is quite a bit of stress placed on them when the suspension compresses. The distance between the wheel hub and your bevel gears is reduced when the suspension compresses and the halfshafts to each hub need a way to compensate for this. If you remove the 1l bushing on the 6L axle, the axle will be able to slide within the hub and will move towards the wheel when the suspension is compressed. You will need some spacers between the hub and rim to keep the axle from hitting the rim.

There will also be some forward/backward movement of the halfshafts as the suspension cycles. The bevel gear arrangement doesn't allow for this movement, but this can be solved by using a u-joint or cv joint instead of the bevel gears. Because a cv allows axles to slide within them, using a cv instead of the bevel gears may also solve the above issue (depends on how much movement you actually need).

<p>Hi, thanks for the comments, i will check the Polaris solution.

Daniel: yes, I tried those set-UPS too, the CV and U joints just don't offer enough movement, neither in angle, nor in slide. The one with sliding inside the wheel hub was a step forward, but still not enough. It works as it is, some silicon spray on the 6.5 DBG axle makes wonder. ��

Still, it works against the suspension, so it isn't going to be the holy grail.

Any further idea is welcome!

Edited October 29, 201410 yr by agrof

Hello Agrof,

Have you seen this suspension build by Nicjasno:

https://www.dropbox.com/sh/0qt73qemhnu35gq/AABJhlywSLVug4suVuOI5waNa/2013-11-17%2016.57.57.jpg?dl=0

I think if you make some small changes and replace the u-joints with pulley wheels you will get far.

If you ditched the portal hub, you could bring the universal joint closer to the wheel itself and you'd be able to fit in another UV joint. This will eliminate some of the friction between the driveshaft and the swing arm.

Thank You guys for the hints, i will not give up yet.

I suggest you to use the natural freemotion of the portal hubs without bushes to let the drive axle slide in and out. This way there is less of a chance of U joint popping out. Still I prefer solid rear axles beacuse they are tough, like this:

I made the pivot points as far from each other as possible, but in the regular way it is still not enough. Even if i put the differential 1-2 stud deeper.

I ran out of ideas, i will build the static version, maybe later i will give another try for making it PF.

Edited October 30, 201410 yr by agrof