Replacing or modifying BH chassis

[trammayo]

The above loco was the first to receive a replacement chassis (Taming a BH). There was nothing wrong with the drive mechanism - sweet as a nut - but rather the pony truck swivel arrangement. The original chassis was laid aside (along with another replacement until I had time to work on the two locos needing attention!

Well anyway, yeasterday was the time.

My Santa Fe BH (an earlier Big Hauler) was quite noisy on the gear side of things. As the chassis from the first loco had red wheels (same as the SF) I chose to use it as the relacement.

Here is the chassis I wanted to use as replacement....


... and the one I wanted to replace ...


pics of both opened up - different motor mounts and gearing arrangements ...


(Note dry gears!)

... and the newer version of the BH chassis...


I didn't want the swivel arm pony truck but, as the mounting was part of the arrangement something needed to alter. Also, on the newer version the axles had proper brass bearings, whilst the original had none. (both methods seen in above pics). The cover plates also show (or don't) the pick-up contacts. In the original, the pick-up were direct from the backs of the wheels.....


The differences as quite obvious. The arced slot for the pony truck swivel, whilst not the best arrangement, is what I prefer for running on the R1s of my trailer set up. The square block with four tiny black CS screws is (or was) the mounting for the truck.

More to follow...

 

[trammayo]

To fit the traditional Bachmann pony truck, I had to get the razor saw out and cut through both covers in exactly the same place. Once this was done it was a case of what would be the best method of rejoining the swapped over cut-offs. I have some UHU hard plastics glue and tried that.. It worked OK but I didn't want to wait 24 hours for final strength.

I cut a flat metal angle bracket into two pieces which acted as joining plates. It was at this stage that I got interupted and forgot (later on) to take pics - thinking I had already done so. So all I have of that particular aspect is a pic of it all assembled with just the screw heads showing! ...

Another aspect I forgot to photograph were the crankpins - totally different on the more modern chassis. In the case of this loco, I cut a spacer in two to take up the slack.

Here's a couple of pics from this morning's project to illustrate the difference..

New type...

Old type..

I had the correct plastic retaining pegs from the donor chassis for the SF loco so all fitted back together well.

On test - no probs! ...


It runs very nicely - smoother and very quiet!!

 

[trammayo]

The third BH that needed to be improved was my Rio Grande Southern - so bad I daren't run it! I have not bought many brand new BHs - and this was S/H purchase.

The replacement chassis was exactly the same as fitted when new - so it was only a question of a straight swap and connecting the wires. I had never looked inside at the 'works' but, during the removal I could tell there had been a few problems. It had also had some new wiring (all in red) so I had to bell it out to find which side they picked up from (didn't want the pony truck having a different polarity).



Once the polarity had been ascertained, it was a simple connecting up job.

The lead weights from the old truck were transferred over - a simple wrap around job with a turn of gaffer tape in each location to provide insulation....


And that was all there was to it - or so I thought!

So out for a quick test - .....

Running a lot better (as I expected) until it crossed the bridge ...

It reached the crossing for the High Level line, derailed and that was that!

The driven axle had come apart, causing the quartering to go awry - the plastic con rods being strong enough to cause the centre axle to do the same on opposite side, and the front one also came loose on the same side as the driven one!

I have had to take it to bits and put it back as it should be. I also put some glue on the end of the square shanks - hopefully they shouldn't come out when set (that'll be tomorrow)!

 

[Rhinochugger]

I'm surprised that the semi-rigid mounted pony truck is better than the double link pony truck - I would have thought that the newer type of mounting (the double link version) allowed more flexibility.

But my gut instinct is obviously wrong - but then, I don't have experience of R1s

Interesting............................but loud !!

 

[trammayo]

I'm surprised that the semi-rigid mounted pony truck is better than the double link pony truck - I would have thought that the newer type of mounting (the double link version) allowed more flexibility.

But my gut instinct is obviously wrong - but then, I don't have experience of R1s

Interesting............................but loud !!

I don't think you're wrong Mike, but the newer ones really only have the flexibility in one plane and lack the vertical play of the original.

R1s are a PITA - they probably make up around 45% of my track in the trailer. I have (more or less) solved the problem of the pony truck derailments by adding weights and creating some superelevation on curves. The numerous points are the biggest problem - the small diameter wheels bouncing or going astray

 

[Rhinochugger]

Aha, the only experience that I have with a Bug Mauler front pony truck, is the one where I changed the wheels, for solid metal (to improve the looks) not realising that it may have given me improved riding

I used Brandbright 32mm gauge wheels, cut the axles in half and extended them to 45mm with resin filled plastic tube so that I could still have split axle electrical pickup on the bogie. I also shortened the bogie, by bringing the front axle forward, to stop it looking like a Bug Mauler

 

[trammayo]

Well the UHU repair glue seems to have done its' job in holding the wheels/axle components together - tried the loco out yesterday....


So that was a sigh of relief. Three locos made more serviceable from two bought in chassis - plus I the two chassis which I had replaced as potential foundations for scratchbuilds! That could end up as being five for the price of two!