Large Scale Central

Bachmann American Front Truck

Problem Solving
#1

I know this has been discussed before but having just replaced half of my trackage I experienced the front truck on my SPC 4 4 0 coming off the rails in various places.

Taking the idea from Kevin Strong I modified it a bit and have solved the problem. Basically I fixed a piece of sheet styrene to the top of the truck frame and drilled a hole to take a small round headed bolt and secured this with a nut on both sides of the styrene. The lower nut is kept from turning by enclosing it in a tight fitting cage made of the same styrene. The bolt was inserted and adjusted so that around 2mm of space was left between the top of the bolt and a cross member under the deck frame.

Result, no more derailing and once painted the styrene is all but invisible. Hope you can see this fix in the pic.

Regards

David

#2

So, this bolt prevents the pilot truck from lifting? Or have I misunderstood?

#3

Yeah, it’s not immediately obvious why this works.

Greg

#4

Yes, the idea is that the top of the bolt pushes against the underside of the deck, preventing the front wheel from lifting off the track. Here’s a photo of the front pilot of my 4-4-0.

On mine, there’s a styrene plate on the underside against which the top of the bolt slides against. On mine, I have it set so that there’s about 1/32" between the pad and bolt when the loco is on the level. That’s not a lot of space, but with reverse loop and spring switches on the railroad, I need the downward pressure on the front wheel to push the points open. The 1/32" space allows for minor dips and twists, but will not allow the wheel to ride up over the points when it encounters them.

If you wanted to go a step further, you could put a spring between the head of the bolt and the front truck, so the force of the spring helps keep things on the tracks. Bachmann uses a similar spring plunger arrangement on their 2-#-# front pilots, and I’ve built similar assemblies for the pilots on my 2-8-0s.

Later,

K

#5

Hmmm. I’ll have to give this a try on my Lionel Atlantic. There is one turnout that it just won’t go through without stumbling. Everything else makes it, including my Botchman 4-4-0. Thanks for posting this, David and Kevin.

#6

Due to manufacturing variations (as in, they’re all different) the pilot, cowcatcher, deck, cylinders can be different heights from the rail and different angles.

I’ve had to heat and re-bend smokebox support rods over the years to get the nose right.

But, the general issue with 4-4-0’s is that you run out of “up” room. Due to the aforementioned variances, the nose lifts, and you hit the stop on the front truck pin, and off it comes. Weight and springs can help…but you have still run out of room. Push down on the front, might work well going forward, but not backing over the same spot, as holding the front down lifts the back of the truck.

What I do, and have done since day one, is remove the truck mount plate, one screw next to each cylinder, and note orientation!

Slip a washer between plate and cylinder saddle, put it together and try it. Add washers as needed (remember…you can run out of “down” room). When satisfied, pull it apart, measure the total thickness of the stack of washers, cut a rectangular piece of styrene for each side, drill a clearance hole for the screw, and mount it up.

TOC

#7

Yes Steve it stops the front of the truck lifting, same as Kevin’s solution but the rounded top of the bolt bears on the cross member of the deck frame so no need to stick another piece of styrene under the frame. Loco used to derail at five locations both forward and reverse, it does not now. In all it took about 30 mins to do.

Regards

David

#8

David, what was causing your front truck to lift and derail?

If you are not sure, where was it happening consistently? You say 5 locations, but what was happening there? What is very interesting is that it happened in both directions.

Are these 5 locations at switches, curves, grades?

It seems there are several situations, which might have different solutions.

Thanks, Greg

#9

I had to restrict the up travel, and ability of my pony trucks to twist, in order to have them not derail going through my spring switches. In an ideal world (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)the lead and trail trucks would actually support some of the weight of the locomotive, and so would not want to lift up and derail as easily as they do.

#10

I meant the other david ha ha!

I remember your item was pushing open a spring switch… (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)

David Bunn, these 5 spots, were they on curves, grades, switches?

Greg