Locomotive Traction Motor Pinion Installation 1

[roryrobb]

GE specifies a hot advance of their locomotive traction motor pinions of .085" to .100".

GM and MKO specifies only .055" hot advance and the taper is basically identical in angle, length and diameter. We are actually going to about .070".

Of about 80 of these motors done, where pinion installation is done by first lapping the tapered seat to the specific pinion, then using heat advance to the specifications mentioned, we are now seeing a couple of the GM pinions slip. We have also encountered a couple of busted shafts.

These locomotives haul 80-100 ton car unit trains full of coal up a 5-6% grade for about 10 miles.

Is anyone willing to provide some advise on installation that may explain these problems?

 

[MikeHalloran]

I have never seen one of these animals, but I'll take a shot.

The pinions are supposed to be induction heated, and pressed onto a self-locking taper, right?

I'm a little suspicious of the lapping operation; it may leave a finish that is not similar to what the factory uses, and may not press the same distance for the same force. I'm guessing you started doing it because you couldn't match the tapers well enough by grinding them independently. Tapers of this sort require extreme precision in measurement, that may be beyond your shop's capabilities.

I'm also suspicious that there may be other shortcuts of which you are not aware, e.g. cold pressing, or not bothering to measure the pinion temperature, stuff like that. This might be offensive to the shop, and might get you a grievance in a union shop, but surreptitious installation of a surveillance camera might reveal your problem. On the other hand, observable installation of a surveillance camera, or something that looks like one, might make your problem go away without you ever knowing what the problem really was.



Mike Halloran
Pembroke Pines, FL, USA

 

[davidbeach]

These locomotives haul 80-100 ton car unit trains full of coal up a 5-6% grade for about 10 miles.

Nope, they don't do that. Saluda was long celebrated as the steepest mainline grade at about 5% and it is no longer in service and I find it highly unlikely that enough motive power would ever have been put onto a single train to run even a 5000 ton train up that hill.

 

[Mendit]

Never lap the motor shaft with the gear. Always use lapping rings and plugs made from iron. Lapping the shaft with the hub will produce a ridge at the top of the shaft and the small end of the hub, then when you install it your only contact is the rigdes. Correct method of install is to determine the required axail advance. Interferance of typical is 0.002/inch, with 0.003/inch of shaft diameters deemed to be the maximum amount of hoop stress the part can handle, Beyond this permanent deformation of the hub can occur. The taper of these gears is I believe 0.750/Ft For reference this is 0.001 interferance for each 0.016 of advance. If your book states 0.085 to 0.100 advance then you can calculate from here.
If your shaft is 4" you will need 4.0 x 0.002=0.008 int
As you requested here is a typical procedure.
1 Clean the shaft free of oils and burrs
2 Clean th hub free of oils and burrs
3 Check contact with machinsts blue (need 85% minimum)
4 Calculate required advance
5 Dry install hub and record distance from back of hub to a fixed part of the motor typical 0.800"
6 Make a spacering in 2 halves 0.700 wide
7 Determine the temp to heat the hub to give the required advance (hub bore in inches x0.000065/temp rise add 80F)
8 Make sure the retaining nut fits the thread easily
9 Preheat the hub (typical 350F) prefer an oven or propane torch (oxy accetylene is aggressive and can cause uneven heating.
10 Clean the shaft apply a thin layer light oil only
11 Secure you spacer to the motor behind the hub (crazy glue works)
12 When the hub is up to temp, slide on to contact the spacer ring and quickly secure with a the nut or retaining plate, allow to cool.
13 Check to ensure hub does not move when you remove the retainer ring.
14 Remove your split ring spacer.

Point to note shallow tapers have nore advance than steep tapers, the maximum I have seen being 1.250/ft on keyless shafts, more accuracy is required the steeper you get.
Good luck

 

[roryrobb]

David
Your probably right, the highway sign going along the tracks says 5 to 6% grades, the tracks are probably not that steep...sorry for the misconception, I stand corrected.

 

[davidbeach]

Highway grade I can believe. The railroad probably winds back and forth enough to 3 to 4 times as long as the highway and therefore have a grade 1/3 to 1/4 as much. Where are you referring to?