Gear Motor Failure Modes?

My shooting club has motorized target carriers on the indoor range. They use "Maxtorq" gear motors, and one isn't working. The motor shaft spins,
but the output shaft doesn't. It doesn't make any excess noise like grinding of gears or anything. These have been in place since at least 1970, and they have been so realible that I don't know if anyone is around who knows much about them.
I suspect either a set screw or Woodruff key has let go in the gearbox, but it's also possible that a shaft has snapped or a gear hub has busted loose. I've never worked on one of these things & was wondering if I should concentrate on finding a spare (we may have some someplace), or try to repair it. If it's likely to be a quick fix, I can leave it wired up & work on the gearbox end. Otherwise I'll have to completely dismount it. The winter pistol league has just started, and we need every firing point we have.
Thanks!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 22 Oct 2009 10:59:49 GMT, the infamous Doug White

I'll bet it's a shear pin that let loose. And in a public setting, it has probably been in service like that for long enough that the broken nubs are worn down and it doesn't make noise any more.
There's likely an inspection or access plate on the geared end so you'll probably be able to work on it live. Just make sure to tape the switch down so nobody accidentally causes you to be one of the targets moving along the line, Doug. ;)
let's see, an array of screwdrivers, a 1/4" drive set, a transfer punch set, a small hammah, and some needle nose pliers oughta do ya. Don't forget the tub of moly wheel bearing grease to re-lube it after you're done. Oh, add a roll of paper towels and tube of hand soap.
Got shear pin-, cotter pin-, or roll pin-sets?
--
A book burrows into your life in a very profound way
because the experience of reading is not passive.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
scrawled the following:

<snip>
I think this was a fairly abrupt failure. It was fine one week, and when I came in to practice several days later, it had a sign on it. We frequently have the range to ourselves on Saturday nights, and the motor was dead quiet, spining merrily.

I'll have to get up there with a ladder & take a closer look. H adn't thought about a shear pin. I don't even know if it's ac or dc. They are operated with a manual 3-position spring return (on-off-on) toggle switch to change direction, and the cords are tensioned such that the pulley slips when you get to each end of travel. I'm assuming it's a reversable ac motor. It looks a bit like one of these:
http://electricmotorwarehouse.com/Dayton/6Z073.htm

I've got cotter pins & roll pins, but no shear pins. Once I get more info off the nameplate, I'll have to see if I can find a manual someplace. There are several different brands on the line from the looks of them. I also need to come up with some sort of clamp or hook to hold the pulley & cord while I work on it.
Thanks for the ideas.
Doug White
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 22 Oct 2009 23:41:08 GMT, the infamous Doug White

So, potentially, it could have been running for days if they're on a gang circuit. YMMV.

Don't forget to check Burden Surplus. They have better prices if they have what you want. www.surpluscenter.com (187 choices today)

Cotter pins are the poor man's shear pin. They're usually soft enough to prevent damage but tough enough not to fail quickly.

A repair manual for those would be a sweet find.

Dat'll be $37.50, please. ;)
--
A book burrows into your life in a very profound way
because the experience of reading is not passive.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
scrawled the following:

Nope. Each position has a spring-return switch & a motor. It only runs for 30 seconds or so each time the target gets run back or forth. You have to hold the switch on.

These guys want the same as Grainger, and I can get a discount there.

I checked out their selection. No joy at the moment. Nothing on eBay either, but I have asearch in place for the future. I've got a catalog in the basement from another surplus outfit that might have something.
<snip>

No luck in that department. I found that the gear boxes are sealed & full of oil, so working on it in place is out of the question. I looked briefly in the back room where a lot of junk is stored & didn't see any spare motors, but they could be buried in a wide range of places.
Doug White
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
as an aside to this thread, I just looked at a couple of gearmotors I had sitting around waiting to be put away - they are 1/3 hp Dayton, 200 in lb torque at 30 rpm - anyone want one or two? they are on the left coast, make me a credible offer (get my email off my web site, www.wbnoble.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I found most of the nameplate data, although it was hard to read:
It's a continuous duty 115V AC reversible split cap motor, 25 in-lbs torque, 124 RPM motor. Maxitorq seems to have gone the way of the dodo, but Grainger has what appears to be a drop in replacement if we get desperate:
http://www.grainger.com/Grainger/items/6Z084?Pid=search
I'm still trying to locate someone at the club who might know if we have any spares stashed someplace. In the meantime, I'll start checking out the surplus places Gunner mentioned and put a search up on eBay.
Thanks!
Doug White
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You might want to consider some of the Oriental Motor models in your search. New ones, at very reasonable prices used to be frequently available on eBay. They're very reliable, fully enclosed, AC reversible PSC gearmotors with ball bearing rotor and gear shaft support.
The OM gear boxes come in a wide variety of ratios, and mount similarly to the Grainger example, with 4 bolts.
--
WB
.........
metalworking projects
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I looked at the OM web site, and their search engine is totally useless. It also appears that their frame sizes are slightly off. The mounting holes for the Dayton/Bison motors that appear to be a drop in replacement are on 2.65" centers. The closest OM has is 2.89", which won't be nearly close enough. I couldn't really find an equivalent motor. There should be plenty of Daytons & Bisons around, I just need to wait until the right one surfaces.
Doug White
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.