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Subject: 
Universal Joint Modifications for Train Applications
Newsgroups: 
lugnet.technic, lugnet.trains
Followup-To: 
lugnet.technic
Date: 
Tue, 4 May 2004 18:39:29 GMT
Viewed: 
2041 times
  
Has anyone modified a universal joint?  Was your modified part successful?

I find that the uni joints are too long for certain train applications.  I
propose to take a broken uni joint (the axle holding parts break at the ends),
and do the following bold, illegal things:

1. Take a uni joint and shave off the broken axle holding part.
2. Drill out the round hole in the axle holding part to 1/8", to hold a flex
tube.
3. Cut down a piece of axle so that it has just over 1 stud length of axle and a
short length of flex tube profile to fit inside the modified uni joint round
hole.  This will possibly be 1/2 stud of axle instead.  The round hole insert
provides the necessary additional support.
4. Insert axle into modified unit joint and, hey presto, a uni joint with 1 stud
(or 1/2 stud) of axle rather than 1 stud of axle holder.
5. Add parts to make an extending shaft that can extend and contract by 2.5
studs whilst transmitting power.  I won't use a suspension spring casing as the
extension needs to be longer than 2 studs length.  I'm trying dark grey axle
pegs in 24mm pulleys at the moment.  It works OK but it's rather fat.  I would
prefer to use modified cams (axles in the 1/2 offset hole and flex tubes in the
others), but I'd prefer a solution with fewer mods.
6. Add two modified uni joints and the extension device together, making a total
length of less than 9 studs, to form transmission for a Shay locomotive.
7. Build 2 more sets of transmission for the other bogies.

I don't like to mod for the sake of it, but I think broken parts are fair game
as they are otherwise useless.  I mod for mechanisms to make things work, not
for aesthetics as it's difficult to get a good finish.

For those unaware, a Shay engine has a 3-cylinder engine hanging over one side
of the loco with jointed extending shafts running the length of the loco to 2 or
3 bogies.  In principle this requires 6 uni joints and 3 extension devices.  The
problem with the Shay is to get the flexible transmission into a very short
length (I'm aiming for 8 studs or less), yet extending and contracting by 2.5
studs as the bogie turns.

Any ideas for alternative solutions that fit the above spec are most welcome.

Mark Bellis



Message has 2 Replies:
  Re: Universal Joint Modifications for Train Applications
 
(...) Mark, I have also been looking at a Shay, but encountered the same problems and put it on hold for a while to let it percolate. I even tried a sliding joint with square tubing, with some success. But I never got around the length of the (...) (20 years ago, 6-May-04, to lugnet.technic)
  Re: Universal Joint Modifications for Train Applications
 
(...) For what I can read, it seems to be a good use for the broken u-joints (yes, they are toooooooo long)... but, can we see the piece modified? It may help looking for an alternative solution. An also, where can I see a Shay engine? I've never (...) (20 years ago, 7-May-04, to lugnet.technic, FTX)

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