Briggs Models Daffasco trucks for Atlas C630: why they don't work, how to fix it

[craigolio1]

Hello All.

I just built three sets of the Briggs Models Doffasco truck conversions for the Atlas C630.  The kit is well designed but I encountered a few issues that prevent it from working as it should.  I have heard people complain about the trucks on this forum so I thought I would post what I did to alter the trucks and achieve an almost Atlas like level of performance.

Complaints I’ve seen are that they are noisy, and that they are not free rolling.  Both issues are a big deal and will be addressed here.

First I should say that the most important part of this kit, operationally anyway, is perfect.  That would be the location of the gears once assembled.  Once the gear box is assembled, prior to installation of the wheels, the gears are perfectly aligned and turn very smoothly.

There are two versions of the kit available.  The earlier version comes with the gear box in two pieces and it must be assembled.  It uses the factory Atlas axle cups to pick up power and hold the axles in the correct position.  The Atlas axle cups are recessed and glue into the Briggs side frames.

The later version comes with a one piece gear box. It replaces the Atlas axle cups with etched parts that the side frames glue onto.  Aside from that the two are very similar.  If you are purchasing the kits still available from Central Hobbies, I think it’s the later version that I think you get.

Unfortunately I didn't take any photos as I went along but if you have the trucks it will be obvious what I’m talking about, and if you don’t then it doesn't matter anyway!



Earlier verision

As far as assembly goes, the early version of the truck is actually my favourite.  I found the way the side frames attached to be more secure.  However the gear mesh needed a little help so operationally I like the later, “improved” version more....   see edit at the bottom.

Problem: Gear mesh/noise/binding:

The gear box is a two piece assembly.  Once the two pieces are together in the jig everything goes together as instructed.  However, I found that there was a little too much width available in the gear box which allowed the gears to very easily slip out of the holes in the etched bearing plate.  This caused misalignment and therefore noise, and in a worst case binding and freezing of the mechanism.

Solution: I cut thin strips of .005” styrene and slid one in either end of both sides of the gearbox between the bearing plate and the outside of the gear box.  This shims the bearing plate inward reducing the space and solving the problem.  I tiny dab of CA holds it in place.  Use thicker CA so it doesn't wick into the bearing plate holes and freeze the whole assembly. 

Problem: Binding on the electrical pick-ups and possible derailments on curves and grades

Solution:  The truck has a higher rounded portionon one side of the gear tower and a lower sloped portion at the other end.  This isn’t mentioned in the instructions but the lower portion needs to be oriented towards the fuel tank end which allows the electrical pick-ups to clear the center portion of the truck when turning.  If the higher end is here it pushes out against the electrical pick-ups reducing turning radius and possibly causing derailment.  Also the higher end could prevent climbing a grade if the easement between the flat and grade is to short.  Mark on the chassis where this bump is located and grind a little bit out.  This will allow the truck turn up towards the front and prevent contact with the frame when entering or exiting a grade.



This completes the modifications to the earlier design and yields a smooth turning, free rolling truck assembly.



Later version


Problem: flexible gear box sides allow gears to slip out and bind or create noise.   The “Improved” version of the truck uses a single piece gear box.  Unlike the previous version, the gears sit perfectly in the gear box.  However, once assembled I found that there was enough flex in the thin sides to allow the gears to fall out.  This flex is needed to allow you to bend the sides out to get the gears in without cracking the gear box, which I still managed to do.

Solution:  I glued thin styrene rods at the ends of the gear box which, after the gear are installed, holds the sides in and prevents them from flexing.  It has be very thin rod or it will contact the gears at one end and cause noise and binding.  I know this for a fact.  Haha.



Problem: Gear box is too wide causing complete binding because the backs of the wheels a pressed against the gearbox and the wheels can’t turn.

Solution: I used a Dremel tool with a sanding drum to narrow the ends, and a pointed engraving bit to do the center section where a drum won’t fit.  Problem solved.

Problem: Friction from the glued on side frames prevents the axles turning freely. 

Sollution:  The instructions tell you to press the side frames on to create dimples for the axle ends to rest in.  I found that this still created a little too much friction so I used the pointed engraving bit in my Dremel tool to make a little cone shaped hole located where the axle points had made marks in the side frames.  Not too big or you’ll break the side frame.  After doing this there were no issues with friction.



Problem: Truck doesn’t turn freely once installed

Sollution:

The tabs, or retaining ridges, that hold the truck in the chassis and allow it to swivel are two wide causing friction and preventing the truck from swivelling freely.  I filed the recesses down and the ridges as well, using the Atlas truck as a guide.  Finally I filled a bevel in the top outside edge of the ridge to match the Atlas truck.  Now they swivel freely inside the chassis.


This sums up my assembly tips.  With these modifications performed they run beautifully and fill a big void for any modeller building CPR or BCR M630s.  Hopefully you can benefit from it and enjoy another interesting detail on some uniquely Canadian models.

Craig

Edit.  When i realized I had installed the first set of trucks backwards, leading me to discover the issue with the high part hitting the electrical pick ups, I had to remove the side frames from all of the trucks and reverse them.  On the "Improved" set, they came off fine but because I used CA to attach them, I never really got them firmly attached when I re-glued them.  Even after sanding I couldn't get as good of a bond and they later broke off doing dome other work.  The fix was to drill a #65 hole through the side frame, through the pre-existing holes in the pick up plates.  Then file off the pins on the site of the trucks, mark the center with a pin and drill a hole there too.  Now a short piece of .035" styrene rod holds them on very tight.  I would do this to them now even if I had a new set and didn't mess them up.  This gives it a really solid attachment which will make handling them less stressful.  With this issue solved the newer version of the truck is my favourite now.

[reinhardtjh]

Bookmarked!!

Thanks Craig!

[peteski]

I have no stake (or is is steak?) in this, but still - excellent writeup!

[craigolio1]

Thanks guys.

The fleet so far:

[mandealco]

Thanks Craig, very useful info.  Nice looking MLW's too.
Cheers
Steve

[BCRail720]

Much appreciated!  I've built several sets, with several more to go, so tips are always helpful.

[craigolio1]

Much appreciated!  I've built several sets, with several more to go, so tips are always helpful.

How do you find they worked when you built them? 

[BCRail720]

I've only purchased the second run, so can't speak to the first run. 

Overall, they've run well.  I had similar problems with the trucks not swiveling, and used the method you described to fix it.  No problems with gears or clearances.  Was worried about the pickup scheme, but it hasn't been a problem.  I did create small dimples on the sideframes that the wheel points sit in so they weren't binding, and so the axles made good contact with the pickup strips - easy to do.

Not a fault of the kits themselves, but I replaced the Atlas wheels with NWSL wheels because I can't stand the look of Atlas wheels.  The NWSL ones look much better, but getting them perfectly aligned and in gauge has been a headache.  Trucks not swiveling freely exasperates derailment issues that come with fine(r)-scale wheels.  To avoid the headaches I probably won't build the rest with NWSL.

[peteski]

Not a fault of the kits themselves, but I replaced the Atlas wheels with NWSL wheels because I can't stand the look of Atlas wheels.  The NWSL ones look much better, but getting them perfectly aligned and in gauge has been a headache. 

You might want to consider using Kato wheelsets as described in https://www.therailwire.net/forum/index.php?topic=33107.0  Almost direct replacement for Atlas (just have to slightly push the half-axles in), they look a lot better than Atlas (dare I say as good as NWSL) and are less expensive than NWSL.

IMO those wheels look really good and they stay cleaner much longer than Atlas wheels.

[craigolio1]

That's a good idea. I've had my flanges turned down to run on C40 rail. I hope I don't experience tracking issues. I don't have a layout to test them on so time will tell I guess.

Craig