I've hit a bit of a snag on a project. I building an On3 2-8-0 with BLI's On30 C-16 drivers. Since the crankpins were out of scale...so far that I couldn't use them with scale 1880s style rods...so I filed them off. This hasn't caused any problems with 3 of the 4 axles, but the screws really aren't long enough for the main driver. Does anyone have a good source?

I'd try Bowser, but I don't want to shell out $12 ($10 min for shipping) for $2 worth of parts...if I can avoid it.

Since I know it isn't cool to mention such a project without a photo...


Btw, that is an old photo. I've done a fair bit of trouble shooting since then and the cross head guide is attached to the main rod.

Can you take a photo of exactly what you need? I am failing to understind this setup. I have an HOn3 MDC 2-8-0 (outside frame) that had worn crank pins. I solved this by drilling out the old ones, glueing in pieces of brass tubing, tapping the inside of the tubing for an 00-90 screw, and then attatching with a hex head screw. The tubing extends through the drive rod and is slightly longer than the rod - that way I can tighten the screw all the way down and the rod has the perfect amount of clearance.

I think these show it better:

Here's the main axle while being modified:


Essentially, I eliminated the old crank pins because they were way too large for scale rods to sit on them. I was going to use the screws as crank pins...as they are around the correct size...but they aren't long enough for the main crank pins.


I've also considered using tubing, but I don't know of a way to cut threads into the outside. Perhaps the solution is to drill out the holes in the driver centers, insert brass tubing, and then add new screws to the outside, much as you've done.

I see now. I wonder if they make small dies to turn threads on the outside of a rod... What size screw are you using? 2-56? I basically drilled a hole in the counterweight, inserted the appropriate size brass tube, and then tapped the inside of the tube for a 00-90 screw. That may not work for you if you are using a larger screw, because the wall thickness of the brass tubing may not be thick enough to allow for the threads on a larger screw.

Edit - I just looked, and K&S makes a 2-56 die. You could use a brass rod, drill out the driver, and press/epoxy the rod in. Then thread the outside of the rod, and attatch the mainshaft with a 2-56 nut.

That drive looks great. I never thought of using plastic for side rods even though some of the big manufactures do. I feel so stupid, why didn't think of that. I've hit a serious snag in the valve gear of my CNJ 4-8-0. It's been sitting untouched for about a year now, and cutting them from plastic may be just the thing because it's so much easier to work with. That pic was just the thing to get me back to work on it.
sorry I can't help with your issue, but I do have a question... what thickness styrene did you use on the rods?[attachment=2299][attachment=2300]

e-paw Wrote:That drive looks great. I never thought of using plastic for side rods even though some of the big manufactures do. I feel so stupid, why didn't think of that. I've hit a serious snag in the valve gear of my CNJ 4-8-0. It's been sitting untouched for about a year now, and cutting them from plastic may be just the thing because it's so much easier to work with. That pic was just the thing to get me back to work on it.
sorry I can't help with your issue, but I do have a question... what thickness styrene did you use on the rods?

Glad I could help! Mine are 0.040" thick...they should be, for such an engine (apprx 28 ton), 2.5" thick. I found styrene to be an easier material both to get accurate rods cut out, as well as to detail. I'll probably use brass for my HOn3 2-8-0 project...once I work my way through the que to get to it.

If I had the material and equipment...I'd go with etched or machined nickel silver for rods. If I was to go with brass...I'd build them in styrene and send them to the Backshop to be burned out into brass. I'd guess that either 0.030" or even 0.040" thick styrene would be fine for an HO 4-8-0.

Kevin, thanks for checking that out. I can think of a few other ways to make it work based off of your helpful advise. I haven't measured the screw size...they were what came with the BLI drivers. I may just replace all of them if I get such a die. Their 0-80 is, according to my caliper, the closest in size (nearly dead on).

Do you have a drill press?

Nope.

If I'm understanding your request correctly you are looking for longer versions of small screws that we normally use in modeling? If you have a hobby shop nearby, do they carry Hobbits? They have screws available in various lengths in sizes 2-56, 1-72, and 0-92. Would those work? You might also try the following site:
<!-- m --><a class="postlink" href="http://www.microfasteners.com">http://www.microfasteners.com</a><!-- m -->

I think the problem with Micro Fasteners is that you probably can't order just a couple of screws.

Russ,
That's a steal compared to the hobby shop! I was looking for machine screws that are similar to those used on the crankpins of our steam locomotives...with a thin hex head.

nkp_174 Wrote:Russ,
That's a steal compared to the hobby shop! I was looking for machine screws that are similar to those used on the crankpins of our steam locomotives...with a thin hex head.

My LHS sells walthers screws in packs of 10 for about 2.99. They probably buy the screws in bulk and repackage them. I Used hex head screws and filed the head thinner - about half as thick as it originally came.

I picked up a set of 0-80 screws. Nearly perfect...except that they are too large! Based on what I've found in the specs online for the ASME, the walthers screws are just a couple hundredths too large...or so my caliper reports. I may try an 00-90 and an 00-80, but I suspect that I'll just make the 0-80 work.

I ordered a few goodies for my hudson project...I need to update that thread...and so I'll pick up the new screws once my hudson supplies arrive (universals and paint).

nachoman Wrote:I see now. I wonder if they make small dies to turn threads on the outside of a rod... What size screw are you using? 2-56? I basically drilled a hole in the counterweight, inserted the appropriate size brass tube, and then tapped the inside of the tube for a 00-90 screw. That may not work for you if you are using a larger screw, because the wall thickness of the brass tubing may not be thick enough to allow for the threads on a larger screw.

Edit - I just looked, and K&S makes a 2-56 die. You could use a brass rod, drill out the driver, and press/epoxy the rod in. Then thread the outside of the rod, and attatch the mainshaft with a 2-56 nut.

Yes , small dies & taps are made . The die is properly called a watchmakers draw plate. it has both tapered holes to pull a wire thru to size it in steps to what is needed, it also has the slotted hole which will then thread the wire . To give an idea of how small a piece can be threaded the hole marked 8 will just pass an.020 wire --7 won't!

The taps are also the same sizes. They are both Metric, but if you are making your own studs & nuts it makes no difference.
I found these on E Bay in jewelers supplies , between them I think they were about 20 -25 bucks , a bargain as far as I am concerned .
I once asked a Swiss trained watchemaker ( they are by & large a snooty bunch) how to how to get something like this & he informed me almost nobody made them any more & it would cost BIG bucks --hundreds!!
I guess , considering that in order to graduate watch school they have to SCRATCHBUILD an entire watch, ALL of it , gears, springs, case , screws, every thing & each piece is examined by the teacher as it is finished-- any flaw == even a scratch & it is instantly smashed with a hammer -- make another!, they have a right to be snooty.!


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Impressive, Dave. Thanks for the background as well.