attach worm gear to motor shaft

[andy chandler]

I am rebuilding Bowser K4s and replaced orginal Pitman motor with skew wound 5 pole and new brass worm gear.  The center hole  in the worm gear is slightly bigger than the motor shaft, so press fit will not work.  What adhesive should I use?  Thank you.  Andy

[tstage]

Andy,

I would measure the OD of your motor shaft and the ID of your worm gear with a pair of calipers.  NWSL makes bushings and may have one that will press fit into your worm gear so that it can be press fit onto the motor shaft.  Much better and more secure than using an adhesive.

Tom

[Overmod]

Several things here:

Any kind of adhesive for other than a close sliding fit will not work well because invariably the worm will be 'cocked' or eccentric on the shaft when the adhesive has set up.  Neither of these situations will give you very smooth running!

The other problem is that drilling out the hole in the worm to accommodate a full bushing may be difficult: you'd have to chuck it on the worm teeth and then use something other than a typical split-point drill in a vise, or else use a lathe.  Neither is something you'd want to undertake.

(t might be difficult to get any sort of interference or press fit on a very thin sleeve unless it is 'hat-shaped' with an edge against the end of the worm.  You'd tap the sleeve into the worm, gently, then put it on the shaft with the hat side toward the motor bell.

If the sleeve is a sliding fit, I'd put it in the worm first, and attach with thin cyanoacrylate.  Then use the same on the shaft, being very, very, very careful to keep adhesive away from the bell.  Epoxy probably requires too much bond thickness to work well here.

[Soo Line fan]

For many years, PPW-A line has sold slip fit flywheels. The recommended adhesive has always been red Loctite.

https://ppw-aline.com/collections/precision-brass-flywheels-1/products/20010-flywheel-cement

I have installed multiple repower kits from them and the Loctite always held the slip fit flywheels on well.

The NWSL bushings that Tom mentioned should work, provided as he stated, the proper ID and OD is determined and the correct adapter is selected.

Looking at images on Ebay of the NWSL bushings, it does not appear they have a "hat" or collar on one end.

PPW - A line also sells them but they too do not have a collar.

My Bowser 4-8-4s have the stock Pitman motor which are 2.4MM. Most can motors today are 2.0 MM.

Measure twice, buy once

[jjdamnit]

Hello All,

tstage

NWSL makes bushings and may have one that will press fit into your worm gear so that it can be press fit onto the motor shaft. Much better and more secure than using an adhesive.

I have used the A-Line sleeves with great success with many re-motoring projects.

An "adhesive" might not center the motor shaft in the new worm gear. This can cause possible future damage to the drive train components.

The A-Line Sleeves- -first pressed into the worm gear before installing onto the shaft- -alleviates the possibility of future wear. 

They recommend knurling the shaft and/or pinning the gear; mechanical solutions over chemical- -bonding agents.

There is the "Suspenders & Belt" mentality that will use both press fitting and a bonding agent.

In my experience, a bonding agent was not needed with properly installed bushings.

Hope this helps.

[andy chandler]

To all posters:  I researched all your suggestions.  Even tried teflon pipe threading tape.  Also, attempted to make my own sleeve from .001" shim brass.  None worked.  Finally, I roughed up the shaft with sandpaper, applied medium viscosity CA. and quickly rotated the brass worm onto the shaft.  This worked perfectley and provides smooth quiet operation.  Almost no gear noise.  In the end, I probably over thought this process.  Thanks for your attention.  Andy

 

 

 

tstage

NWSL makes bushings and may have one that will press fit into your worm gear so that it can be press fit onto the motor shaft. Much better and more secure than using an adhesive.

 

 

I have used the A-Line sleeves with great success with many re-motoring projects.

An "adhesive" might not center the motor shaft in the new worm gear. This can cause possible future damage to the drive train components.

The A-Line Sleeves- -first pressed into the worm gear before installing onto the shaft- -alleviates the possibility of future wear. 

They recommend knurling the shaft and/or pinning the gear; mechanical solutions over chemical- -bonding agents.

There is the "Suspenders & Belt" mentality that will use both press fitting and a bonding agent.

In my experience, a bonding agent was not needed with properly installed bushings.

Hope this helps.

 

[/quote]

jjdamnit

Hello All,

 

 

tstage

NWSL makes bushings and may have one that will press fit into your worm gear so that it can be press fit onto the motor shaft. Much better and more secure than using an adhesive.

 

 

I have used the A-Line sleeves with great success with many re-motoring projects.

An "adhesive" might not center the motor shaft in the new worm gear. This can cause possible future damage to the drive train components.

The A-Line Sleeves- -first pressed into the worm gear before installing onto the shaft- -alleviates the possibility of future wear. 

They recommend knurling the shaft and/or pinning the gear; mechanical solutions over chemical- -bonding agents.

There is the "Suspenders & Belt" mentality that will use both press fitting and a bonding agent.

In my experience, a bonding agent was not needed with properly installed bushings.

Hope this helps.

 

[Overmod]

Note that the recommended 'knurling the shaft' is the functional equivalent of sanding heavy scratches into the shaft, but by raising a large number of almost-identical 'peaks' of the same height and perfectly (enough) concentric with the shaft axis all the way around.  Tapping the worm over the knurling would self-align and lock it... the 'valleys' between the knurled points would probably admit either a curing adhesive or suitable anaerobe if additional post-securement were desired.

Pinning the worm might be more work than worthwhile.  You'd need to drill a radial hole in the worm between teeth (and contact surfaces on the worm flanks) and a registered cross-hole of comparably tiny cross-section in the steel shaft, then make a suitable pin to go in the hole and be upset, crimped, cemented, etc. to survive bring slung free at peak motor rpm.  If you think slightly magnified gear misalignment noise is uncomfortable, just wait until the tiny pin starts scraping the tops of the worm-wheel teeth...... 

[MisterBeasley]

I have a BLI Hudson locomotive that stopped moving.  I took it apart and found the worm gear slipping on the motor shaft.  This is designed as a press fit, so it should not have been slipping.  I used a drop of CA on the shaft, slid the gear over it and have had no more trouble.