Machine Shop / Locomotive Drive Work

[Jay Criswell]

Chris,

Sure they are available but I made a choice. I even wrote about it in my post. Maybe it wasn't well written, or clear. I wrote, " If using the MXL timing belts and pulleys they would have to be very small in diameter. The problem with using the smaller diameters is, not very many teeth are engaged and the belts can slip. cogged belts slipping is a really bad thing. They will destroy them selves in no time. Because the trucks on the model (Overland SW1500 w/Flexicoils) has such a short wheelbase and not much room between the bolster and gearbox I decided to use brass sprockets and the matching Delrin chain. The sprockets start out as Delrin but I have them burned out and cast in brass (think lost plastic). These won't split and I can install set screws instead of relying on a press fit. Also don't have to worry about them slipping."

Jay

[Chris Webster]

Sure they are available but I made a choice. I even wrote about it in my post.

Thanks Jay. Facebook decided to only show me the first 4 or 5 sentences of your post over there.

[Jay Criswell]

Chris,

You should have seen something like "see more" at the end of the part you were able toread. Typically, it's in blue letters.

I'm saying that without really knowing exactly what you were shown. I'm just relaying a typical scenario.

Jay

[R.K. Maroon]

I recently posted photos of a Hines - FA Simon cast aluminium mill gondola and mentioned I had another. It arrived with a sheared kinpin machine screw:



I don't recall offhand if this is a #2 or a #4, but either way it is pretty small. Since it is steel in aluminum, I am thinking it could be seized beyond the limits of an extractor to remove it (assuming that one is available that small and that I could drill a hole down the centerline of the shank).

I am soliciting suggestions on how to proceed, on the very real possibility that there is some old shop trick here that I don't know about.

Jim

[Rufus T. Firefly]

Center drill and left hand tap?

[Chris Webster]

I don't recall offhand if this is a #2 or a #4, but either way it is pretty small. Since it is steel in aluminum, I am thinking it could be seized beyond the limits of an extractor to remove it (assuming that one is available that small and that I could drill a hole down the centerline of the shank).

I'm thinking the screw broke because it was sheared off by the truck during an impact -- if that is what happened, perhaps you could use an engraver bit in a mototool to cut a slot in the screw, and then unscrew it using a screwdriver blade inserted into the slot?

I also wonder if one of those really tiny supermagnets could be used to turn the steel screw?

[Rufus T. Firefly]

I don't recall offhand if this is a #2 or a #4, but either way it is pretty small. Since it is steel in aluminum, I am thinking it could be seized beyond the limits of an extractor to remove it (assuming that one is available that small and that I could drill a hole down the centerline of the shank).

I'm thinking the screw broke because it was sheared off by the truck during an impact -- if that is what happened, perhaps you could use an engraver bit in a mototool to cut a slot in the screw, and then unscrew it using a screwdriver blade inserted into the slot?

Interesting idea!

I also wonder if one of those really tiny supermagnets could be used to turn the steel screw?

Creative.

[R.K. Maroon]

Yes, it would be smart start with the "maybe it's not seized" possibility. I had success one time on a screw that broke under impact, a possibility suggested by Chris. My solution there was to drill a tiny hole that was a slip fit to a known wire size. I either superglued or loctited the wire in and presto:



I want to say I used the "shaft lock" version of Loctite, but can't say for sure. Note that my efforts to drill down the centerline of the shaft were not very good, but luckily in didn't matter. It would have mattered more if the idea failed and I had to drive the screw out.

Jim

[bob turner]

I agree - try a slot. Maybe cut with a Dremel disc that is almost worn out. If you need to center drill, look for a left-hand drill? Or just go in there with a #60 and cutting fluid.

Or - carefully measure, go in from the other side, and punch it out. Re-drill for a 10-32, tap the hole almost through, plug with brass, and re- drill.

[R.K. Maroon]

Thanks everybody for the input and ideas on what to do about the broken screw in the cast aluminum gondola. I decided after dinner last night to "get 'er done".

Attempts to back the screw out, on the hopes it was loose, failed. I then drilled a very small hole down the center of screw. I could feel it as it broke through the screw into the bore. It went a little further before bottoming out. That told me how deep I could drill with out breaking through the casting. Consecutively larger holes were drilled until the screw was gone. As an aside, this produced a lot of powdered corrosion, not unexpected. Once the screw was out I could see the original bore at the bottom of the hole I had been drilling. I recentered on that and drilled a new hole using a #1 drill, which is a bit smaller than 1/4".

I then made a bushing with 4-40 internal threads, using 1/4 brass rod. The outer diameter of the rod was turned to be a snug slip fit to a #1 hole:



Finally, I faced the bushing until it fit flush. This required inserting the bushing into the gondola as a fit check, and then removing it to take off a little bit more. Having the bushing threaded made removing it easy: just insert tap (or a screw) into the bushing and turn it -- the tap threads into the bushing until hits the bottom of the bore and then jacks the bushing right out of the hole. Once the length was good, I secured it with just a half-drop of regular thread locker. Done:



I have said this before, but will say it again: Having a Unimat or other small lathe is essential for restoration work of this kind.
Jim

[bob turner]

Looks great! Cast aluminum is not known for holding threads anyway.

[Rufus T. Firefly]

I decided after dinner last night to "get 'er done".

Neatly done

[Chris Webster]

Bill Davis has a repowered OMI C630 up for auction:
Ebay #353168949961, BRASS O Overland Reading C-630 Low Hood C/P NO RESERVE

Bill's auctions always have nice photos; this listing includes two pictures of the mechanism. I presume the repowering must have been done by Stew Kleinschmitt since the mechanism has two motors, a clutch and a massive flywheel.

[De Bruin]

Rather interesting variant there Chris with those paired motors running a single shaft out one end, I've certainly never seen that before.
Anyone else?

[E7]

Yes, it would be smart start with the "maybe it's not seized" possibility. I had success one time on a screw that broke under impact, a possibility suggested by Chris. My solution there was to drill a tiny hole that was a slip fit to a known wire size. I either superglued or loctited the wire in and presto:



I want to say I used the "shaft lock" version of Loctite, but can't say for sure. Note that my efforts to drill down the centerline of the shaft were not very good, but luckily in didn't matter. It would have mattered more if the idea failed and I had to drive the screw out.

Jim

Jim, What type of lubricant is that above your hand?