Model Train Journal

I built a nice CLW H10b a couple years ago. The drive shaft from the gear box measured .187" and the Pittman motor I used has a .157" shaft. So I used a piece of model airplane fuel tubing (DU-BRO Cat. No. 222) which fit nice and snug and gave me nice running quality for over a year of use.

Recent things changed and upon inspect that fuel hose has shown the tendency to twist in the area between the two metal drive segments. Note there was an approximately 1/4" span of hose in the middle, and that's where this new twisting has occurred. So now my nice running engine is apart and undergoing analysis as to what would be a better connection ( I recall Bob Turner Toyota hose) I think that was what it was. I've also tried a metal coupling similar to the one NWSL offers but made of brass and have not had it run to my satisfaction. Is there a recommended spacing between the two drive parts? Should they be almost touching to possibly prevent the tube twisting which has started on my engine? I'd buy one of the better quality drive coupling such as SDI offers but there listings of such things sort of leave me cross-eyed and unwilling to spend $ without further investigating...which leads me to MTJ for some experienced words of wisdom...Thanks

Robert

I forget what the optimum diameter is, but a sleeve of K&S tube can not only increase diameter but also lengthen the shaft.

The Toyota hose is simply extremely high quality windshield hose. Purchase at dealership. Longer piece is cheaper than shorter piece. Or just use cheap stuff.

Yes, one secret is shafts close together - but the other secret is - longer worm shafts avoit torque wrap-up. Lengthen the worm shaft, not the motor shaft.

Does that help?

Well it refreshed my memory as far as that Toyota windshield washer hose is concerned. What is the inside diameter of that particular hose Bob? My current configuration has a gap of 3/16" between the ends of the two shafts in question.

The relatively soft fuel hose I originally used ran fine for a year before it eventually wanted to twist right in that 3/16" gap. Now a fresh piece of the same hose wants to twist right away also has me wondering. I disassemble the running gear and cleaned and relubed it all on the chance it had become mechanically resistant. But that didn't help.

More words of wisdom please, and thank you.

Robert

3/16 is okay. Go get the hose. I may be able to find a part number. I think it works on 3/16" dia shafts, but you will find 5/32" shafts out there. Slide a piece of 3/16 OD tube on such shafts and solder or Loctite in place. If you solder, tin the shaft lightly first.

Not 100% sure this is it, but it sounds right

https://www.amazon.com/Genuine-Toyota-9 ... uctDetails

The number I had from way back is:

Toyota vacuum hose: PN 90999-92004

Rich

Not trying to create controversy. That was Bob's number which I copied way back when.

Thanks Bob...hose is on order. You feel it is worthwhile increasing the motor shaft size up to 3/16 ? It's currently 5/32"

Robert

Probably. Try it first. Let us know if that part is correct - the different part numbers are probably length. The stuff is miles ahead of other similar products.

As I recall, you could coat the shaft with Pliobond, then cinch down with a piece of safety wire, used like a hose clamp.

That sounds like a workable solution...once I get it all back together, and test it out I will report on my results. Thanks again Bob.

Robert

This is the product I ordered.

HOSE, VACUUM TOYOTA 4RUNNER 88-95 LAND CRUISER FJ62 0EM GENUINE 90999-92003
It seems the five digit suffix just associates with a particular Toyota vehicle. The hose I received was exactly what I needed ( Thank you Bob Turner )

Inside dimension measured slightly larger than a .125" drill bit...probably 9/32" It provided a really snug fit on the gearbox shaft, and ever so slightly looser on the Pitman shaft...still a nice fit and I used a small tywrap on that segment to assure of non slip performance. Engine was put through a break in period to "seat" the new part. It works very well. Once I get the boiler assembly back on it will be back to normal. Although I do need to chase down a few squeaks somewhere in the mechanism. Thanks for the help.

Robert

All squeaks resolved and this beauty can return to service now. Pictured here with workmate D16sb 4-4-0 ready for service.

Robert

This is old news but during the final phase of this repair I discovered another drive train point worth mentioning. This came up when I was final testing the engine. There was a noticeable hesitation upon initial powering, then it would run free a few inches and the hesitation would again occur. After a fair amount of investigation I discovered a solution. I left the motor to rest free in its rubber saddle...meaning I did not use any type of tie down to secure the motor in place. As soon as I allowed it to rest free and essentially remove what was a forward force on the driveshaft into the gearbox...everything operated smooth as silk. The motor is adequately captured in place by the boiler...and loco runs as nice as it did prior to having to make the original repairs first discussed in the beginning of this thread.

Robert