graupner u-joints breaking ???

[Radek2]

We broke a few now trying to assemble them the center coupling snaps when you try to squeze them together, too much fibre not enought plastic? I even tried to file the guide to slide in better and still broke another one...
any one know to to assemble these without breaking them?

[EMSPAUL]

Try freezing them for about twenty minutes .
Paul

[Radek2]

just the center yoke? to shrink the metal? the piece that breaks is not in the picture it is the part that goes between the two pieces looks like a H and when you squeze the yoke into the H one of the tabs snaps off. its frustrating anyone out there use these things,

[PondProwler]

I am using commercial grade couplings if the shaft and motor will allow.
One inch in diameter and also in length with compression clamping action around each shaft.

[Thefarside]

I use them on my Tug, I just find a drill bit the same size as the blank hole in the cross, use the back end of the drill in the hole and lever the cross in place. It's a smooth running joint, Hope this helps.

John

[pkboo]

Try opening the joint ends just a tad with a small longnose plier and inserting the centerpiece in between, I´ve never had problems with them. GL Boo

[Stu :)]

Nor have I had problems with them.
I dip the 'forks' into some hot water (tap water hot 50-60ºC, not boiling!) to soften the plastic, spread the forks with a hemostat or the aforementioned pliers, drop in the metal joint and cool at room temperature. If the forks seem disformed from the "warm spreading" I bind them with a rubber band to encourage them back into shape; but not TOO tight.

Stu :)

[Radek2]

thats exactly what myself and my friend did inserted a allen driver into the blank hole then pushed it in and were successfull on two out of four of them.

we are not having any problem on the pieces that set screw onto the shafts its the piece between them that looks like a H that snaps even with light pressure :eek: . what do you guys think about not using that center piece just glueing my bulkhead a little closer to the z drive?

[Rob_P]

I like them because they are nice and short.
However I recently broke one of the plastic sides off after an extended period of trying to get the pin to engage into the hole.

Next time I will make sure there are no burrs around the hole preventing the pin dropping in & warm up the plastic.

I went down this self assembly route because it was the only way I could get the correct combination of drive / driven bore sizes.
Maybe they know we will break xx% of them and have to buy more!

PS - There are two options, just join the equipment together as per the top photo or you can get an extended mid section to give extra articulation.
I'm going with the shorter assy.

Rob

[Kmot]

I do the same as Stu. Except, I run the hot tap water and just hold the plastic end under the tap water for a minute or so, then the metal star will push in easily. I then squeeze the plastic end closed again with my fingers and it forms to it nicely.

[Radek2]

its the extended mid section that we snap no problems with the pieces in the photo,

with just the parts in the photo that should be enough to do the job right?

[Rob_P]

The middle piece adds an extra articulated joint.
Its not strictly necessary unless your alignment is off.

[Kmot]

Heat the mid section the same as the end section to assemble or disassemble them.

[Shaun Hendricks]

I just used my fingers and didn't have a problem with them. Put the cross pin in one side of the yoke, pried it apart and pressed on the cross piece at the same time and it popped right in- no heating or cooling.

I am not using the center piece as my motor shaft is aligned to the prop shaft on 1 axis. The center piece is only needed if it's not aligned at all.

[Radek2]

thanks guys for the info, there is no alignment problem so I am going to not use the center piece.

are these pretty stout?

[Shaun Hendricks]

I'll let you know when I break one... :D

[CaptLee]

Radek Been using them for 20 yrs and only broke two and that was on disassembly. The pin that fits or a drill bit shank seems to work for me. The answer of single or double is it makes no real difference which you use. Double is with the "H" installed, use it mostly to make up for a length problem or a out of line driveshaft. prefer the Single setup myself, both ends and a spider.

[AndyKunz]

I had trouble with them as well, until somebody suggested I put the U-joint inside some surgical tubing. It stiffened the joint, so it didn't bend as much, but that was OK since the joint was only there to remove minor misalignment anyway (unlike the one in Kmot's picture).

You might lose a little power, but I haven't lost a joint since.

Andy

[pkboo]

I had some probs with the bigger ones, 2mmx2.3mm are fine and yes the tubing, you can even use silicon fuel tubing, is usually the solution. Boo.