Show me your Universal Joints

Have tried and no improvement .

Yes I have contacted Mike in PM. He experimented similar issue but at much lower level. Adding Dupont Teflon spray helped a lot. He is doing that regularly. Have tried with similar product WD40 but it did not worked for me. He told me that only Dupont spray worked on his platform but actually not possible to order that spray in Europe (out of stock every where). Might give a try as soon as available.

OK thanks for your proposal, I will PM you my email.

Cheers,
Olivier

I use heavy duty rose joints

similar to this

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTPmovG6o3mKwNvWKWp8zhukUWXAFc5vpoCXQ&usqp=CAU

hi Oliver
I don’t know if heim joints were ever designed for constant high pressure use like that from your example video. It’s like a worn knee joint and nothing will fix that. You should be running on a ball bearing surface.
The first post above you can see the U-Joints I made from 7075 Aircraft aluminium. They are very strong.
I can make more but I would make your ones bigger and stronger. if you really want to over beginner them for safety, then make them from machined steel.
I’d probably start by making just one set for you to test to its limits and see if it’s strong enough. I imagine it only needs to hold 150kg-200kg max?
PM me if you want to discuss manufacturing some of these.
Also I wonder if there’s a bearing based rose joint or heim style pushrod that you can get that is higher rated so you can just plug and play.
cheers
Matt

Hello Matt thank you very much for your help,

In fact even if the platform is 700kg, I think the weigh/force could be much more than 200kg but looking at professional 6gof that use U joint at the top, they look not so big compare to yours. What is the diameter of your needle bearing? do you have the spec of it ?
Looking at the professional platform I see that the needle bearing diameter are approximatively the same diameter of the visible part of the rod end diameter, so for my platform should be around 3/4" diameter.

I need to check how I could adapt my platform to replace rod end by U joint.

My biggest constrain is the height of my garage where the platform is installed, ideally I should not extend the length of the current arm. So will have to shorten then as U Joint are longer that rod ends to keep the same total length.
I do not have professional software for the design, I have I made all the design with sketchup from which I can import 3d model (or sketchup model) only .

Can yo provide me a 3D model of your U Joint to see how I could build that on my current platform ? (I will send you a PM for this)

Thanks Olivier

Needle bearings. 20x55
ie 20mm diameter and 55mm from tip to tip.

AU $9.73 | 1piece 20X55 MOCHU miniature U-joints UNIVERSAL JOINTS BEARING Universal Joints Crucetas Joints de cardan
https://a.aliexpress.com/_mNjdQ8P

Hello Matt,

Have few other questions:

1)Do you know how much radial charge 20x55 U-Joint can handle ? Have tried to find this info into catalog but could not find spec for it.

2) Choosing bigger U-Joint (eg 28x69), will that change a lot in term of total price ?

3) I think there should be as well 2 x 360 bearing as in your picture here
So I need to consider that for the integration on the top of the arm on one side and on the bottom of my platform for the other side. Can you export a 3D model from your Solidworks project so I can import it on my sketchup project (to see what are the size of the full U=Joint and how I could integrate it)

Thanks Olivier

Hi Oliver.
I’m not sure what radial charge is. You can probably find most specs on the supplier websites.
Changing the trunnion size affects the UJoint size a lot which affects material size and machining time.
No, I won’t be sharing my SolidWorks Model sorry. You should try making one in CAD. It’s fairly easy but takes time to test and think about collision points.
a 3D printer is a must for prototyping too.
Also my piston part of the actuator is able to rotate, so I don’t need 360 bearings on top or bottom. The image you show was the old top and bottom joint I used and I didn’t like it because it allowed the whole actuator to possibly spin at very obtuse angles.
For any price info, perhaps you should PM me.

What is your joint angle of attack at the starting point ? When you are in the “drive position”. Did you designed your rig so the bottom and upper joint have same position at start ?

Sorry I don't know what you mean for 'joint angle of attack'.
When I'm on drive position, both top and bottom joints are aligned at the same angle compare their respective ball.
Joints with Misalignment Spacers allow 60° angle (compare to 17 without spacers) so at drive position it could be any where within this 60° (I can rotate the arm anywhere from 0 to 60°). I probably don't need 60° (even on extreme platform angle) but thought it was safer to have large angle.

Do you see any issue with this ?

Could it be that those high angle spacers cause the squeeking noise?

When the joints run without those spacers, they have two very smooth and perfectly matching surfaces rubbing against each other. That shoud be fairly smooth and thereby quiet.

But when you utilise those large angles that the high angle spacers give you, the smooth inner surface of the joint body will rub over the gap between the "ball" and the spacer.

Could that be the cause?

I just asked if you don’t hit the limits but I believe you that with such spacers it’s not the case. I designed bend legs to have them all aligned (90deg. to the horizontal plane) in “starting drive” position in order to maximize their range.

I would explore @Dirty ’s idea. Maybe those spacers are responsible of noise. Anyway, painful investigation. - good luck

@Olivier beaujoin maybe you can put your rig in a small/slow loop mode then put your hand on the joint. Or attach a vibration sensor like an iPhone to it to diagnose the exact location. I will try and video the movement of my standard U-Joint. Regarding angle of attack, I attempt to mount my joints so they are in the middle zero degree mode so they have the best chance at full flexibility in all directions.

FYI here are some of my U-Joint prototypes, 3D prints and a final version.
The final version I made to have both a flat bottom to mount to my floor base. And an optional threaded top/boss to mount on my actuator rod end.
That way I could manufacture 12 sets and use them either at the top or bottom of the actuator.

The degree of freedom is limited mechanically on purpose ?

Yes I have limits on the DoF. The less freedom, the shorter I can make them, and the lower my overall platform for the size of actuator. I did not want any bigger than this.

Shorter/Squat U-Joints are also stronger for their size.
And currently the degree of freedom is more than double what I need.

If I made them taller to get more freedom/angle (which I don't need) then I would need to add more material for strength, and that wouldn't look as nice.

If I see correctly, those joints are not rotating vertically on ball bearings, right ? What are your dof limits ?
I use
120 surge sway heave
10 - 15 - 25 yaw roll pitch

Here I see an interesting design. You save some length by mounting them laterally and you have almost unlimited degree of freedom.




Do we need such angles and if those doesn’t lock is another question

My DOF Limits are set differently depending on the game, and I keep them lower than their max limits.

My actuators have 400mm travel @ 500mm/sec
I usually have
300mm heave and 150mm surge and sway, but I can have much more.
25 degrees Pitch and Roll, and 15 degrees each side of centre for yaw.

I often just run at 50% of this which is still enough for most needs.

I love the 1st One you show here. Great design. Where can I get the .stl file for one?

Hey guys who sells these need buy asap im in Sydney.. pls PM me cash waiting