National Motors

[John_Galt]

What is your method for removing a stuck field from a gearbox?

What is your method for straightening a bent rotor shaft?

Centrifugal switch & mechanism tricks?

How do you address coasting?

How do you remove a bad bearing from an endbell?

Repacking bearings?

What other tips/tricks/advice do you have about Nationals?

Thanks in advance,
Chad

[Coors]

Re: National Motors

Originally posted by 070 002 612:
What is your method for removing a stuck field from a gearbox?

<font size="2" face="Verdana, Helvetica, sans-serif">put the bolts back through the feet the opposite way to push the motor off. if the bolt isnt long enough, i back the bolts out and then add washers between gearbox &amp; motor, then more washers.

What is your method for straightening a bent rotor shaft?
rotate rotor, whack with a hammer on the high side, and/or grind/file the shaft.

Centrifugal switch &amp; mechanism tricks?
install 610-309-042 or A-110-663-500

How do you address coasting?
check carbon brushes, chassis contacts, capacitors.

How do you remove a bad bearing from an endbell?
gear puller, or vise hammer &amp; punch/socket.

Repacking bearings?
always

What other tips/tricks/advice do you have about Nationals?
good quality electronic cleaner to clean/bathe windings with. use heavy guage wiring to replace the old. if you have an air compressor, blow motors out while on the machines, frequently

[amfpinboy]

Re: National Motors

One way to seperate the field housing and gearbox is to remove the three bolts and tap the housing around so that the holes are covered. Then thread the bolts up from the bottom and push the housing off the gearbox. Use WD as the shaft starts to pull out. The BE motor works about the same way. You can only screw in two bolts from the reverde side, so a large screw driver comes in handy to help pry the housing off. If the shaft gets bent, lay it on the bench and spin it by hand. Find the high point and hammer the shaft down a bit with a heavy plastic mallet. You can true up the shaft without too much trouble.
New carbon brushes should stop any coasting. Stretch out the springs a bit when you re-assy the head.

[JimDorsin]

Re: National Motors

sorry didnt recognise your new (again) name... I wont waste your time.

[Pindecked]

Re: National Motors

I LOVE them Jap Matsu****a (National) motors...run like tanks..&amp; never leak a drop [img]/content/btubb/images/%%GRAEMLIN_URL%%/laugh.gif[/img] [img]/content/btubb/images/%%GRAEMLIN_URL%%/143.gif[/img]

HA !!! Censors won't let me spell MatsuPOOPa Motors

[Andrew]

Re: National Motors

What is your method for removing a stuck field from a gearbox?
As above - tap sideways and bolt backwards (and large screw drivers). Another general rule we have is not to separate a motor from its gearbox while on the machine (and always use as a single unit). But, well, that might be unnecessary fussiness. Also, we use anti-seize grease in the connection (so actually, we hardly have a problem seperating them, and rarely need to do it anyway).

What is your method for straightening a bent rotor shaft?
If it's enough to cause poling on a national motor, then we'd probably get it re-turned (depends also if the keyway or bearing interface are also worn, which is often coinciding). I can see that the hammering technique would work too (i.e if you dropped it and it was bent, but the bearing interface was okay).

Centrifugal switch &amp; mechanism tricks?
All of our are (Cyber) SSSS. So I can't adequately advise on the original National centri-mech.

How do you address coasting?
We've rarely had a coasting National motor. They tend to get worn sweep shaft splines presumably because they brake so well (i.e. the motor stops on a dime and the poor spline takes the hit). They (as all dynamically braked motors) are sensitive to the brake circuit in place. That includes contactor, caps, and start-switch (if you have ones that affect braking). The National gearbox is non-loaded (unlike the GE or Westinghouse). It relies on electrical braking for stopping and carbon brushes for staying still once stopped. But, because it is designed that way from the get-go, it retains that characteristic over time. The GEs on the other hand rely on the loading of the gearbox to prevent coasting (once stopped) and thus get worse over time as the gearbox surfaces wear. However, if you find one coasting, and still does it with a chassis change (eliminating the contactor), then test it on the bench. If it has any hestitation in stopping (after several attempts because it might sometimes stop perfectly and sometimes not while not under load), then renew the carbon brushes (as amfpinboy said).

How do you remove a bad bearing from an endbell?
Do you mean the gearbox side cap containing the bearing cone? For that we made a tool which is basically an egg-shaped peice of flat 7mm(?) steel with a bolt going through a threaded hole. You can get the flat peice in under the bearing and then tighten up the bolt. We found our bearing pullers either didn't fit or the small ones fell off too easily (maybe we just have crap bearing pullers).

Repacking bearings?
Don't like the idea of repacking bearings. Obviously only non-gearbox bearings should have seals or grease (the bearings in the gearbox should not). But when adding grease to a sealed bearing, you (without sufficient laboratory conditions [img]/content/btubb/images/%%GRAEMLIN_URL%%/wink.gif[/img] ) tend to introduce contaminants, and/or wreck the seal. All to save, what, $5-10 for a new bearing? Especially with a National that should not have to be touched in the bearing department for years - why risk having to revisit it earlier? But I can see that other shops are more careful and can do it well.

What other tips/tricks/advice do you have about Nationals?
-If you have Nationals and GEs, put the Nationals on the sweeps. They stop better and their stopping ability lasts longer than GEs.

-Grease the keyways/shaft hubs.

-Always replace keys whenever you get a chance - a key is easily replaced, a shaft keyway is not. Use softer key material so that the key dies before the shaft does. If you find that your keyways (shafts) are chewing out without the keys actually being damaged then you should find softer key material. We buy it in lengths.

We actually have a few backend motors with plastic keyway inserts. It's an ingenious idea. The plastic insert sits on the shaft (using a smaller diameter, but with the keyway on it). Then, a plastic key sits in another key way on the insert and inside the hub. When the plastic fails, the insert and key can be replaced and the shaft is perfectly fine. You can also try plastic keys in the normal shaft keyway, but we haven't found any that lasted as long as the soft metal key material that we found. I'll try to find specs/numbers for it if people want (it's standard stuff - just softer than the shafts).

Cheers,
Andrew.

[JimDorsin]

Re: National Motors

Originally posted by Andrew:


Repacking bearings?
Don't like the idea of repacking bearings. Obviously only non-gearbox bearings should have seals or grease (the bearings in the gearbox should not). But when adding grease to a sealed bearing, you (without sufficient laboratory conditions [img]/content/btubb/images/%%GRAEMLIN_URL%%/wink.gif[/img] ) tend to introduce contaminants, and/or wreck the seal. All to save, what, $5-10 for a new bearing?

<font size="2" face="Verdana, Helvetica, sans-serif">Thank you!

[Smokey]

Re: National Motors

I never repack bearings. Waste of time.

We weld our keys to the shafts. This prevents any movement, which in the long run is what causes your keys to go bad. Just tack them on either end.

Hammering a bent shaft will only get it straight to a certain extent. Your best bet is to buy a new shaft.

[John_Galt]

Re: National Motors

Thanks for the good responses, guys, and special thanks to Andrew for another excellent dissertation on this subject, as with so many others in the past!

Never thought of the welded key, that's a pretty sharp idea!

I didn't know the backwards screw trick either. Good stuff, thanks again guys.
Chad

[Rep]

Re: National Motors

Originally posted by 070 002 612:
Thanks for the good responses, guys, and special thanks to Andrew for another excellent dissertation on this subject, as with so many others in the past!

Never thought of the welded key, that's a pretty sharp idea!

I didn't know the backwards screw trick either. Good stuff, thanks again guys.
Chad

<font size="2" face="Verdana, Helvetica, sans-serif">The backwards screw works great, sometimes that's all it takes, get the motor up that little bit when it's tight and it pops right out. We use that all the time

[BigMort]

Re: National Motors

With regards Centi-mechs &amp; Centi-switches I replaced them all with Electric start swicth 090-004-550(50 hz) with some easy rewiring, but for 110v use 090-005-560(60hz)&amp; it should be a doddle. I have replaced about 2 or 3 switches in about 7 years &amp; no rewinds. Happy Daze!!

[John_Galt]

Re: National Motors

Mort,
Never knew you could use the Franklin switch on a National, but I guess it makes sense! How did you come about this little trick?

[BigMort]

Re: National Motors

Dumb luck mainly. tried various electrical switches from local motor merchants without any real joy. Then tried the franklin switch but the problem was it operated on 110v, so I had to split the run winding to find the center tap &amp; put the switch in there. Guys running them on 110v can just place the switch before the run winding. The cost of a franklin switch against the cost of a new centi-mech &amp; a new centi-switch was less than half price, with the added bonus that with no moving parts inside the motor there was nothing to come loose, drop into the motor &amp; short out. Best thing I ever did with the nationals. The theory is the same with westinghouse motors as well. I've just started using them on those as well.