Sticky Dnepr clutch

[mark_in_manchester]

Johnnyr48 PM'd me about a sticky Dnepr clutch, and I thought it would make a useful thread, maybe.

MiM>
So we're both straight...I'll assume you're using a Ural / dnepr box and flywheel, where clutch rod goes down the middle of the shaft and a small square peg on the end locates in a small square hole in the engine-most plain plate, behind which 6 springs sit. There are two friction plates splined to clutch shaft, and 3 plain plates - the one we've mentioned at the back (with 'circles' cut into back for spring ends to locate on), a very boring one in the middle, and a slightly less boring one at the front which screws onto 6 pins with countersunk screws. (Note - it's a really scary sound when these screws come undone and start to eat the gearbox. Do them up tight and punch the slots into the plate / use threadlock or something).

Hard to change gear...you suspect clutch drags. Does it (or is it just hard to change gear) - put in gear, pull clutch in, and try to kickstart. Should feel almost no drag at all.

If clutch does drag - first thing is to check clutch rod is long enough, and level arm at rear is not bottoming on box body. One of mine has a semi-permanent bit of a nail jammed in between lever arm and the 'slot thing' on which it pushes - which means more clutch disengagement. Sorted things lovely. A more permanent repair would be to build up the 'blob' on the arm which is meant to do the pushing with weld, and file it to shape.

Jr48>

...im assuming ive buggered the friction plates in my clutch,it just isnt working - when i get time i´ll strip it down (groan!!!! it has to be the most difficult clutch in the world to put back in - it only takes me half a day now!). im using the dnepr box and thats why it seems more difficult to set up right - this whole semi-automatic adjustment of half a mill(seriously?).did you do the beautifully engineered bit of a nail adjustment for any particular reason? my clutch (when it was working) seemed to have very little engagement,considering the manual says to change gear slowly,not possible on mine - but i am wondering if the interesting? forward controls ive made have quite a lot to do with it? nothing like the standard gearchange, obviously

[mark_in_manchester]

OK, well if clutch is dragging then plates are not separating enough. This may be because actuating rod is not pushing the plain plate on which it engages, back far enough (hence my rusty nail). Or it may be because plain or friction plate(s) are warped (you won't know till you get it apart, but it seems unlikely). Or it may be that something which should slide apart when spring pressure is released (friction plates on clutch shaft splines, or plain plates on 6 big holes in their periphery, which slide on pins bolted to flywheel) is not sliding, but getting stuck. This is less likely with this kind of clutch than the more common 'basket' types which suffer when the basket edges get notchy, but perhaps it is still possible. I'd examine the splines carefully.

If your clutch shaft is not RIGHT IN THE MIDDLE of the whole assembly, then as it rotates the friction plates will try to drag the clutch shaft around the circle whose radius is described by the degree of misalignment. Since the shaft can't do that (it's in a rotation-only bearing), then the friction plates will get shunted across the flywheel and back, even with spring pressure present. This will rapidly anihilate the splined centres - so have a look at all those little teeth.