Truck To Body Mount Couplers - Kato F7B

[BCR751]

I have been asked to do a thread on how I converted the Kato F7B from truck mounted to body, or more accurately, frame mounted couplers.  This isn’t an easy task.  It requires some fairly major surgery to the frame and a complete fabrication of the new mounting system.  I have provided accompanying photos to make it easier to follow along.
Everything I started with: (The original trucks are at the top, the 'revised' ones at the bottom of the photo)



Prior to doing anything to the model, I put it on a test track to check runability and coupler height.  The first thing that stood out were the truck-mounted rapido-type couplers.  These were instantly removed and MTL replacements installed.  The coupler height was far too low which wasn’t a big issue since I planned to remove the truck mounted ones and figure out a way to body mount them.  Further study of the trucks revealed an issue with the tabs that contacted the frame for electrical pick-up.  On both trucks, one tab was higher than the other which caused the unit to list to the left.  I tried filing the high tab down but this caused the unit to be  unstable where one set of wheels would come completely off the rail.  Not good.  I checked the Kato website and, although the original trucks were no longer available, there were some ‘revised’ ones still in stock (Kato Part #929122).  I ordered two ‘front’ trucks which had no coupler pockets.

While waiting for the new trucks to arrive, I decided to tackle the new coupler mounting arrangement.  I took the two halves of the frame apart and removed the motor and drive train.  The Kato unit frame is one big weight.  It fills the entire shell.  Therefore, any coupler mounting has to be done on the actual frame, not on the carbody as is usually the case.  The frame is one of the split variety that has insulating plastic spacers on either end.  In order to insure that there are no shorts, the coupler mounting screws need to be free of any metal.  This requires the milling of notches in each end of the frame.  The notches are 0.200” x 0.200” and 0.130” deep.  I used a Dremel tool with a medium sized milling bit.  Be sure to wear safety goggles as the small metal bits fly all over the place.



To span the notches, styrene strips made from 0.040” x 0.188”, 0.670” long (Evergreen #148) are fabricated.  Once cut, center and drill two 0.050” (No. 55 bit) holes 0.140” in from each end.



Using these pieces as templates, drill and tap 00-90 holes in each end of the frame to a depth of 0.130” as shown in this photo.



Using the small MTL coupler mounting screws, attach the styrene strips to the frame.

*Note:  MTL had/has two types of coupler mounting screws.  One is black and is 0.150” long with a flat head.  The other is silver, 0.250” long and has a rounded head.

Cut two pieces of 0.100” x 0.188” styrene (Evergreen #178) just long enough to fit in the milled end notches.  With the strips in place, slide these pieces into the notch and glue using MEK.  If there is any material extending past the styrene strip, just file it off flush with the strip.



Re-assemble the frame and temporarily install the trucks.  Place the unit on a piece of test track and, using a height gauge like the MTL MT-1055, measure the difference in height between the top of the gauge and the bottom of the newly installed styrene strip on each end of the frame.  This is the thickness that will need to be shimmed to insure the couplers are at the proper height.  Remove the trucks.



Using a pieces of styrene strip at or very near the thicknesses previously measured, cut them to a length of 0.288”.  Glue these on top of the styrene strip flush with the rear of the strip using MEK.



Now comes the tricky part.  Drill and tap 00-90 holes centered horizontally on the above strips as close as possible to the front and rear edges of the frame.  If the holes are too far forward, there won’t be enough material to hold the screws.  If they are too far back, the coupler will interfere with the motion of the trucks.



Attach MTL 1015 couplers using the long (silver) MTL coupler mounting screws.  Do not over-tighten or you will strip the threads in the styrene.

Reinstall the trucks and test the swing.  If there is interference from the coupler, the plastic fingers holding the sideframe to the truck body end adjacent to the coupler will need to filed.  Keep in mind that this arrangement will allow the unit to run on a minimum radius of 14 inches so not much swing is needed.  Some trial and error is required here.  Only file off as much material as required to get to the required amount of swing.  Too much filing may result in the truck coming apart.  Put the unit on a test track and test run it.  Hopefully, if all work has been done correctly, it will perform as it should.



Another tip.  If the unit sounds like a coffee grinder, try ‘beardenizing’ it.  Instructions can be found elsewhere in TRW.  Believe me, it makes a whole lot of difference.

Doug

[Nick Lorusso]

Doug, Looks great. What unit is this going to B?????? Just need the True Scale Couplers on it now.

[arbomambo]

I'd like to see this setup with the trucks and body shell on...
what does the coupling distance look like?
Bruce

[Tom L]

One other thing I have done to my Kato F's of this vintage, is to put a small spring on the pick up tabs to improve the contact to the frame. I think I used a MT coupler spring cut in half and I kind of screwed it on to the tab. I was having very intermittent "slowdowns" (it wasn't very noticeable unless I ran two together) and this seemed to help.  Don't care much for the tab to frame design.

Tom L
Wellington CO

[BCR751]

I'd like to see this setup with the trucks and body shell on...
what does the coupling distance look like?
Bruce

Once I get a bit further along on the shell, I'll post a photo.

Doug

[craigolio1]

Excellent tutorial Doug. I have a Kaslo Shops resin FP9 shell on an Atlas GP38 chassis which has no provision for a rear coupler. I think this procedure might just be the ticket!

Thanks.

Craig

[nkalanaga]

If you want to avoid a little of the work, nylon 00-90 screws are available, and should be plenty strong enough for mounting couplers.

[mmagliaro]

Micro Trains makes a "coupler conversion" for these that provide a rounded plastic insert and coupler for the nose end.
So one could save some work by using that, and doing the milling and mounting pad only on the rear one.

I think this is a very clever solution, but I too would like to see what it looks like with the shell on.
I have tried to cobble a body mount coupler directly into the frame, and it always seems like it cannot fit without
hitting the back of the truck unless the coupler is mounted so that it sticks out way too far.

[BCR751]

This conversion was done on the F7B.  I don't know how one would do the A unit but the MT conversion that Max mentioned is likely the best way to go for the front one.

Well, as in most everything, there are trade-offs.  Yes, the coupler does stick out further than one would like but, in my opinion, it isn't a show stopper. (I consulted Mr. Goodenough on this project and he says the look is acceptable )  Mounting the coupler on the frame leaves very little room between it and the truck.   I did use the shortest shank coupler available and put it as far out on the mount as I could.  As mentioned, some filing may be required on the front of the trucks to ensure enough clearance.  You won't be running a model with this conversion around a 9-inch radius but it will run perfectly on radii 14-inches and up.

I will post a photo when I get further along on the shell.

Doug

[randgust]

I'm running an ABBA set of those, and for me, well, essentially I cheated.    MT on the noses of both A units, and substituted Caboose Hobbies Unimates (short shanks) where the Rapido couplers were for the back ends of the A's and both ends of the B's  The coupling distance is really close, appearance excellent.  I don't uncouple the ABBA consist anyway, so this worked well.

[arbomambo]

I'm running an ABBA set of those, and for me, well, essentially I cheated.    MT on the noses of both A units, and substituted Caboose Hobbies Unimates (short shanks) where the Rapido couplers were for the back ends of the A's and both ends of the B's  The coupling distance is really close, appearance excellent.  I don't uncouple the ABBA consist anyway, so this worked well.

same here...
my priority is prototypical close coupling...
I'll sacrifice the body mounting to achieve close coupling; I prefer unimate (red caboose) short shanks on the 'B' ends of all of my cab units...Z scale couplers in the pilots.
If the body mount couplers could achieve close coupling, then I would be very interested, but, otherwise, I'll stick to the truck mounted unimates.
Respectfully,
Bruce

[peteski]

I wonder if the couplers which were used in the old-style 4-wheel passenger trucks (1017) would work here?  They have a very shallow draft gear box.

[randgust]

Yeah, probably would.   That's the box I've used on a lot of critters, too.

I've bugged Joe for years about offering that box as a separate part.   If you leave some of the extension on, you can either glue or screw the extension plate to a lot of things.

[Mark5]

Yeah, probably would.   That's the box I've used on a lot of critters, too.

I've bugged Joe for years about offering that box as a separate part.   If you leave some of the extension on, you can either glue or screw the extension plate to a lot of things.

Is this the one? Or is it something different?

http://www.modeltrainstuff.com/Micro-Trains-N-1017-2-Pass-Car-Couplers-p/mtl-00102025.htm

Thanks,

Mark

[thomasjmdavis]

Is this the one? Or is it something different?

http://www.modeltrainstuff.com/Micro-Trains-N-1017-2-Pass-Car-Couplers-p/mtl-00102025.htm

Thanks,

Mark

Well I see that those are new and improved.  But I can tell I am getting old because I am having sticker shock over all the reissues and improved versions of stuff I was buying 20-30 years ago.  In this case, not only did I pay a lot less than even the MBK discount price, but the ones I bought in the old days came with wheels, axles and sideframes at no additional cost.