Micro Machining Question

[WVBill]

Why not get a piece of rod stock, say 3mm in diameter cut to the proper length to replace the axel. Drill out the drive wheels and drive gear slightly under-sized and press-fit them to the new axel. If you score a line along the length of the new axel you could use it as an index against two of the quartering marks on your drive wheels.

 

[timb]

Ah. Stub axle with a (delrin?) gear/axle center. Have you considered replacing the whole driver/axle set with a more traditional one-piece axle (Bowser comes to mind) and possibly a NWSL gear or gearbox? Might depend on how your chassis bearings are set up if it could accomodate and the one-piece may have some electrical isolation considerations as well.

 

[hwp]

Tim, you raised a good point that I should have mentioned earlier and that is the two drivers must be insulated from each other as they both have metal hubs for transferring the current picked up by the driver surfaces to the frame and the motor. As a result I cannot use a solid metal axle. I have been through the Walthers and NWSL catalogs and can find no suitable replacement axles or gears. In additional, Bachmann not longer still have repair parts for these locos. So I am left with trying to find a way to make what I have operational. /forums/images/graemlins/smile.gif

 

[timb]

As a last resort - Bowser makes replacement chassis kits for several popular engines from other makes - including several versions of the Bachmann 4-8-4's.

If you've put time and energy into detailing and/or painting the 'body' to your needs - it may be possible and easiest to put one of the robust Bowser running chassis underneath and keep the old girl on the rails.

Bowser Chassis for Bachmann Engines

The price is well within your stated limit - and I know that you'll get a very sturdy (and repairable) chassis out of it.

 

[scott_vt]

hwp,
Any chance you could get replacements for those drive gears. By the sounds of it, thats were your problems initially arose from the bores becoming worn and allowing the axles to move?

scotty

 

[scott_vt]

hwp,
I forgot to mention that we Stock Drive Products for many of our gearing needs at work. If you know the gear diameter, pitch and number of teeth, in your case it looks like 24, you should be able to get a replacement. Unfortunately delrin does not lend itself to being glued, but you could have some one rebore the old gear and make a bushing with a slight press fit and then realign your drive wheels on a surface plate and pin the assembly in position. I will try to leave the link to this company. Hope this helps in some way.

http://www.sdp-si.com/

scotty

 

[WVBill]

hwp

Do I understand correctly that the gear mounts to the stub axle of the drive wheel (as shown in the red line of the attached picture)?

If that's the case, could you drill the gear in a position that matches the hole in the drive wheel for the side iron and use a longer pin to pin all three of them together (as shown by the green line)?

That doesn't solve the indexing problem. But since they don't have a common axle what kept the two drive wheels indexed to each other before?

 

[hwp]

Yes, the gear has a hub on each side and the stub axles fit into the hub. The stub axles were originally pressed into the gear oriented to give the proper quartering. Over time, stress on the pressed fit has caused the axles to break loose from the gear hub.

The good news is that I just found a Tool & Die shop that will do the job for me at a reasonable cost. They are going to cross drill the axles and hubs, insert a locking pin and use Locktite to hold everything together. /forums/images/graemlins/smile.gif

 

[mwechtal]

By the way, if anyone wants to see what a <font color="red"> REAL </font> Micro-Machinist can do, check this out.

Jerry Kieffer

When he makes a scale model, he makes everything scale.

I saw an article where he had a picture through a microscope of a 0.020" diameter tap he was machining. And yes, the decimal point is in the right place.

Mike

 

[timb]

Extremely nice work. Some people just have an incredible talant (and patience) for this type of work.

This one by Pierre Scerri always knocked my socks off...

Ferrari 312pb

I can't find a working link to the video of the model - but suffice to say - it works. Perfectly. A 1/3 size Ferrari with working flat-12 engine and full transaxle. It's a treat to see craftsmanship like these guys exhibit.