Bascule Bridge Problems

[jwb1323]

Update on the project: as noted, I have completed the counterweight with extra weight inside. I had weighed the bascule section, and it came out to 8 ounces and originally tried that as a weight value for the counterweight, but it looks like that wasn't enough to counterbalance the other parts of the trunion mechanism and overcome friction. I added all the other self-adhesive weights I had on hand, and wound up putting around 11 ounces in, which still doesn't "balance" the thing, but makes it perceiptibly easier to lift the bascule. I will try adding the racks and applying power after church and lunch today.

I think a big key is counterbalancing, as noted above. But if you've counterbalanced it, I think whatever the capacity of the motor and mechanism, you can go ahead and use them. The issue with the Tortoise as I see it would be you've got to convert the Tortoise motion, which is travel through at most 30 degrees of an arc, to travel through almost 90 degrees in the final movement of the bascule. To do that, you're going to have to have a lot of additional bellcranking or whatever, and you'll lose mechanical advantage and add friction. Theoretically, if the bridge is well enough counterbalanced, you might just be able to have one of those hot wires move the bridge, but this is THEORETICAL and doesn't take things like friction into account.

[jwb1323]

IT WORKS!!!!

I finished assembly of the racks and the gear cases or whatever they are, applied power from the 12V DC leads, and ran it through 4 or 5 up and down cycles. Checked the motor, very cool. Mechanism sounds good and smooth.

The only problem is what the MR review and the MM article both noted: the limit switch doesn't work. They both suggested replacing it with a Radio Shack part, but actually I think that would be more trouble than it's worth -- it's just as easy to line it up by eye. Regular operation will be via a center-off momentary SPDT switch with steering diodes. I can interlock it with a second DPDT or whatever switch that won't let me run the motor until I've set the signals to red.

I deviated from the instructions in only three placs. I either threw out or couldn't find the pins that are supposed to hold the racks 49, 50, 51, 52 to the rod at the top of the bascule span. I made substitutes up out of styrene tube, a few minutes work.

Parts 46, 47, and 48 don't hold together very well, so I made rectangles of .020 styrene to reinforce the joints.

And I added about 11 ounces of self-adhesive weight reinforced with silicone glue to the counterweight. I just don't know if the thing would work without the weight, but when you consider how cheap the self-adhesive weights are, they're plenty worth it.

That's it as far as deviation from the instructions. I painted and weathered all parts before assembly, but will need to touch up here and there.

The only thing I have to adjust is that the counterweight rubs against the top of a Walthers bridge track section when the bridge is raised. I will first sand the top of the under-track girders to see if this lowers the track enough. If that doesn't work, I'll file a little off the part of the counterweight that rubs.

Summary:

1. This is an advanced kit. Be aware.

2. Take your time. The instructions are well thought out, and they are in a particular order for a reason. Follow that order!

3. When assembling the motor and gearbox, test each step as you complete it. Be sure everything runs smoothly, gears mesh, etc., before moving to the next step. It's a little tricky to get all the pieces to seat correctly inside the motor house. This is essential! But it CAN be done.

4. Note my remarks above on drilling out the holes where the bronze rods and pins go. Test everything to check for smooth operation.

I agree with Otto that the thing is what it is, and it's quite a bargain as I see it. I think I paid something like $60 for the kit at one of the discount places out here. I'm a little concerned that it's plastic, and I still think if Overland came out with an equivalent for $2000 or whatever, it would be worth the money, and I would think hard about replacing the Walthers. BUT there is nothing else like it on the market!!!

But even if you don't motorize it, I think it's worth the money just as a photo prop. When I get scenery and track laid up to it, watch out!!