Film-Tech Forum ARCHIVE: Rebuilding Strong Platter Motors

This is topic Rebuilding Strong Platter Motors in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=010000

Posted by James Ness (Member # 4631) on 07-25-2009, 06:30 PM:

I wanted to read the tutorial on this in the 'Tips' section, but everything in there seems to be down.

Does anyone have this information saved?

Posted by Adam Martin (Member # 641) on 07-25-2009, 06:34 PM:

Define "down". The document appears to be working fine.

Posted by James Ness (Member # 4631) on 07-25-2009, 06:40 PM:

I was getting a 404 page not found error on all browsers.
They work now though, that was strange. My bad!

Posted by Monte L Fullmer (Member # 2797) on 07-25-2009, 11:26 PM:

Yep, just did two more motors this week with gone brushes ...

Let me add an addendum on this above tip that I made for Film-Tech on platter motor replacing: AMTEK/Lamb have now used a different field winding procedure that, on a motor rebuild that I posted back in 2005 which shows using the smaller sleeve on the motor shaft, it will requre the usage of the 1/2" sleeve since this modified winding makes the motor run a bit slower, thus this larger sleeve is needed to compensate for the slower turing motor.

thx-Monte

Posted by Louis Bornwasser (Member # 3063) on 07-26-2009, 08:01 AM:

The hardest part of the "procedure" is getting the excess parts off of the new motor. I use a bandsaw, but a hacksaw works as well. You make a saw kerf at just the right place, put a flat blade screwdriver in it and twist; thus releasing the unwanted and "sawn" part. Louis

Posted by Mark Gulbrandsen (Member # 72) on 07-26-2009, 08:40 AM:

Monte,
I think there has also been a change in the brushes as well. Just clening up the armature and installing new brushes causes the motor to run the same way a new one does... slower and with less torque. There's more to the problem than just the field winding.

Mark

Posted by Tim Reed (Member # 137) on 07-26-2009, 09:12 PM:

The brushes have to be run-in, Monte. Before installing, hook the motor up to a makeup table and run that sum bitch wide open for about an hour or two. Then it'll run faster.

Posted by Monte L Fullmer (Member # 2797) on 07-26-2009, 11:30 PM:

What I usually do - after putting it back on the tower: I plug the MUT in and let 'er rip for a good while to get them brushes seated to the 'com'.

I also leave the back off so I can actually see how the brushes are going and also this lets the air flow from the front impeller be unobstructed when I run the motor at full rip.

Tim, still play your banjo? I bet you're good at it...

-Monte

Posted by Tim Reed (Member # 137) on 07-27-2009, 09:35 AM:

I wish. No, I haven't had the ol' banjo out for some time (I think my wife even sold it). The strings were too close together on the neck and I could never get my fat fingers to mash down on just one string at a time. I'd always end up pushing one string against a fret just fine, but dull the adjacent strings because my fingers were wider than the distance between them. They say there are banjers with wider necks, but I never saw one.

I can't see how anyone could play a mandolin.. their strings are closer together yet! So, I'll just have to remain impressed by anyone who can play a musical instrument. I did get me a harmonica a few weeks ago... don't really know why. The jury's still out on whether I will follow through on that one. [Wink]

Posted by Monte L Fullmer (Member # 2797) on 07-27-2009, 02:14 PM:

(not to drift off-topic) I've been in music since early grade school-it's like golf: a relaxing hobby to have-you're own paradise of sorts.

Harmonica's are fun to play as well. Just take some time to get used to finding the intervals and making them work when you inhale and exhale along with using the tongue armature.

Back on topic - I had help from another tech on how to do these platter motor retrofits - anything to do to go past having to get parts from the factory..in saving the dough.

-Monte

Posted by Mark Gulbrandsen (Member # 72) on 07-27-2009, 03:53 PM:

quote: Tim Reed
run that sum bitch wide open for about an hour or two. Then it'll run faster.

Actually the instructions that come (or at least one time came with) with the new brushes tell you NOT to do that. They tell you specifically to run it in at a lower speed for the first few hours then gradually increase the speed as the new brushs seat. The reason for this is simple in that the contact area on a new brush is not only smaller but it is also probably uneven if the armature is at all grooved... which they usually are to some extent. The unseated brush just can't transfer as high of current as the motor would draw wide open. Another way to seat the brushes almost immediately is to cut garnet cloth in strips just slightly narrower than the armature and run it back and forth under the brush. The brush will then take on a contour much more like the armature itself. You should still run it in slower but it will seat properly much faster.

If you talk to the tech guys at Amtek they will tell you much the same...

Mark

Posted by Louis Bornwasser (Member # 3063) on 07-27-2009, 05:56 PM:

We assemble, clamp in a vice and run at fairly low speed as Mark describes. At some point the pitch of the brush whine will increase, TWICE. You are now finished. Louis

Posted by Randy Bowden (Member # 587) on 07-31-2009, 06:26 PM:

I've been doing these for AMC for a little while now. I replace the brushes, armature, bearings, and tires. After all that it's pretty much like a new motor. I run mine in at about 40% of variac full speed.

Posted by Andy Bajew (Member # 5330) on 08-01-2009, 01:50 AM:

quote: James Ness
I was getting a 404 page not found error on all browsers.

That's the Drafthouse for you, James.

Posted by Mark Gulbrandsen (Member # 72) on 08-01-2009, 05:56 PM:

Randy,

Non need to even replace most armatures unless you're rebuilding these on location... just take a fine cut or two with an extremely sharp small round nosed cutting tool on the lathe. They work like new and will last as long as film does...

Mark