Power train question...Tomytec repower project

[wm3798]

I've got the frame stretched for my re-powered Metroliner, basically cutting the Tomytec drive to separate the truck mounts from the motor mount.


I cut away the bits of a dummy car frame, and everything is fitting together nicely.

But I'm at a loss as to how to extend the drive shafts. 

I was expecting metal rods with press fit ends that could easily be reworked with longer rods, but the drive includes one-piece plastic shafts with tiny universals cast in place...

Is there a practical an permanent way to make these longer?

@randgust ... I'm looking in your general direction for this one...

Lee

[dem34]

Find a drill bit a hair skinnier than the rod. Nib the rod in the center then drill out a piece of solid styrene rod and press fit and glue?

[CRL]

Try to find some brass or aluminum tubing with an ID matching or slightly smaller than the shaft diameter to use as a sleeve. You can sand the shaft slightly until it fits. Use penetrating Loctite to set the length.

[Chris333]

+1 on tubing to lengthen the shafts.

[wm3798]

I guess I'll take a moment to rummage through the stacks of stuff to see if I have something suitable.  Otherwise, off to Hobbytown tomorrow!

Lee

[Steveruger45]

Lee,  see this post of a similar stretch job.
https://www.therailwire.net/forum/index.php?topic=45919.msg597877#msg597877

[randgust]

I have the entire assortment of K&S tubing & rods so it's pretty easy.    I cut the plastic driveshaft in half , and then added a center piece of brass rod, and ACC''d brass tubing over top of the two splices.    Not all that much to it, the original universals are still in there.    You can do this to any Tomytec to adjust the driveshaft length longer or shorter.

[CRL]

I have the entire assortment of K&S tubing & rods so it's pretty easy.    I cut the plastic driveshaft in half , and then added a center piece of brass rod, and ACC''d brass tubing over top of the two splices.    Not all that much to it, the original universals are still in there.    You can do this to any Tomytec to adjust the driveshaft length longer or shorter.

This may be a dumb question, but instead of using brass rod with tubing sleeves, why didn’t you just use a long length of tubing to join the split shaft? After all, automobile drive shafts are hollow tubes rather than solid shafts to reduce flex & resulting whipping.

[randgust]

I could have.   The trick on these is getting the length 'just right' so that you aren't flopping around between the universals or so tight that you're restricting the truck vertical movement.    I think in this case it was more that I had very little left of that size tubing!     

They used to do a square cross-section driveshaft like Kato's 11-105, now it's a thicker circular shaft.    I just tend to splice up with whatever is handy at the moment and works as it's just not that hard to do as long as you focus on getting that length where you want it before you hit the ACC on that last joint - I usually have it installed first and lightly glue it rather than try to get it right and then install it.

[wm3798]

So I've got it back together, electrically connected, and the shell on.
It runs smoothly enough, but the only contact point between the shell and the frame are the two black tabs at the middle, and the bottom edge of the window glass on the top of the frame.
With the shell off, it's pretty quiet, but with it on it vibrates like crazy.
I added some friction tape fore and aft, which helped buffer the noise, but I'm wondering tf there's something else I can try...

Lee

[Steveruger45]

So I've got it back together, electrically connected, and the shell on.
It runs smoothly enough, but the only contact point between the shell and the frame are the two black tabs at the middle, and the bottom edge of the window glass on the top of the frame.
With the shell off, it's pretty quiet, but with it on it vibrates like crazy.
I added some friction tape fore and aft, which helped buffer the noise, but I'm wondering tf there's something else I can try...

Lee

Could you glue some additional styrene tabs each side of the frame, close to each end and maybe support each pair at  each end with a cross brace to prevent them collapsing inward when you put the shell on?

[wm3798]

Here's the almost finished drive.


A couple of highlights from the ground up:
I was able to use the sideframes, including the truck mounted coupler pockets, from the original Bachmann dummy frame I used.  The axle dimples lined up perfectly with the Tomytec low friction trucks.  I simply removed the original axles and cut out the bolster frame from the top of the truck.  A little filing to allow for the width of the pick up shoes, and voila!  They snapped right on, square and level.

I cut some stabilizing blocks out of Evergreen .250x.375 rectangle tubing.  These are screwed to the floor using the holes provided in the Tomy truck plates.  A couple of shims enable me to screw the original top weight from the old Bachmann drive over the top of the whole thing to give it a nice rigid frame.  This definitely improves the vibration of the drive.  I did have to Dremel out the weight to make it nest down properly over the Tomy motor.

The red wire you see there is the jumper between the frame pickups, which I had to cut in half to extend to the new truck centers.  There's a black wire on the other side...  Note that the photo shows the shell in the reverse position of the drive... oops!

When assembled, the drive runs smoothly without any binding, but I'm still getting the vibration through the shell.  My next steps will be to solder in the headlight, and to apply the friction tape to try to mitigate the noise as much as possible.

As it is, it's at least as noisy as the original Bachmann drive, but with much less friction in the drive train and with much better speed control.  A few more bits, then another test.

Then I have to get to work on the layout in earnest... Rho is getting on a plane to Chicago in less than an hour, and won't be home until Tuesday!

Lee