Source of Maxon/Faulhaber 4:1 Gearheads

[metalworkertom]

What caused those teeth to separate from the case (especially since now you think it is all made form a single piece of metal)?

Once you cut through the case there is nothing to support the teeth.  So the cutting tool bends them until they just break off. A light facing cut cleans it up except the tooth profile. I'm going to try cutting a case down with my Jewlers saw. A slitting saw might work well too . Might try and set that up on the lathe. A mill would work with the slitting saw. So I might bring it home tommorow.

[SkipGear]

Tony, I think that gearhead looks great.  The noise isn't bad at all.  It will not be audible in an engine.
So, I have some of those I picked up from eBay a while ago.  How did you mount it on the 1219?
Got any pics?

The scary part, nothing is holding the gearbox onto the motor. It is a press fit over the normal 5.5mm thread. It is a slip fit over the threads but the last mm or so is a shoulder that it is a very tight fit over. Made sure the cut was true and the correct length and then pressed it on. The motor gear is one of the plastic  planet gears from the stage just before the final stage. I thought about trying to press the metal sun gear off of the prior stage but the plastic gear hole was the perfect diameter for the 1219 motor shaft. The metal gear, if I could get it off, would need a bushing from what I can see.

It's honestly pure luck how simply everything came together. I saw the exploded picture on e-bay and thought that I could make it all work together, never thought it would be that easy.

[mmagliaro]

Super cool, Tony!  But... how would you make sure it stayed together?  I mean, getting lucky so it press-fits onto the motor is one thing.  But won't it work it's way off?   Or is it really that tight?

[SkipGear]

Super cool, Tony!  But... how would you make sure it stayed together?  I mean, getting lucky so it press-fits onto the motor is one thing.  But won't it work it's way off?   Or is it really that tight?

It's that tight, but just the same, when I'm fully satisfied that it is going to work, I'll probably put a dot of CA on it to make sure it stays. That goes against my principals of make it serviceable but....I have a dozen of these motors, I can sacrifice one for the cause.

[mmagliaro]

It's that tight, but just the same, when I'm fully satisfied that it is going to work, I'll probably put a dot of CA on it to make sure it stays. That goes against my principals of make it serviceable but....I have a dozen of these motors, I can sacrifice one for the cause.

If it's that tight, then maybe Walthers Goo.  That stuff really holds once it sets up, and it sticks to Delrin better than anything
I know of (the motor nose/threads
are plastic).  And if you really have to, you can still always pry it off.

[mmagliaro]

So, I relented and made a tool for pulling the threaded inserts out of Faulhaber gearheads.   This is a little less "hillbilly" than my two screwdrivers trick.

[narrowminded]

Looks good @mmagliaro.  This is getting easier every step!  

I'm going to be as much as a week getting at this for real.  In the meantime, it seems like the diameter of the threaded end cap is 8.5mm.  Do you have one handy to get an honest number on?  I will need a sleeve to clear that end and still catch the body and when assembled I can't get an honest number until I get the first one apart.  The diameter and thickness would be nice to have for making a pocket that the part can clear.  It's not absolutely necessary but would make life easier if that number was known.

Oh, and I also ordered a tap.  It's US stock so should get here this week. 

[mmagliaro]

I measured my threaded inserts and got 0.335" with a caliper good to .001".  So metalworkertom's number of 8.5mm
is probably right because it is probably metric and 8.5mm is .3346"

Length of the threaded insert is 0.119", and again, since it's probably metric, it's probably 3mm, which would be .1181"

[narrowminded]

I measured my threaded inserts and got 0.335" with a caliper good to .001".  So metalworkertom's number of 8.5mm
is probably right because it is probably metric and 8.5mm is .3346"

Length of the threaded insert is 0.119", and again, since it's probably metric, it's probably 3mm, which would be .1181"

That's excellent @mmagliaro .  Thank you.

I'll probably allow an 1/8" and a little bore depth to clear the thickness.  Do you have an 8mm housing sufficient for dimensions?  I'm thinking that one tool with a body grip adapter could be used for both the 10mm and 8mm gear case.  That might have the 10mm bore depth a little deeper than otherwise needed to be sure it clears on the 8mm housing.  It seems like a good idea to do this once the effort is started.  It would also have to clear the 8mm end cap flange. 

I'm curious how you're measuring the new end bore to get the new press dimension?   I might make a go/ no-go plug gauge for that.

[mmagliaro]

I'm not sure what you mean by, "I'm curious how you're measuring the new end bore to get the new press dimension?"
But I think you mean, "How am I measuring how deep in I go and how wide I cut into the inside of the can so I know
the threaded insert will press in correctly."

Well, to be honest, I'm somewhat just eyeballing it.  I set the gearhead in the lathe chuck, put a boring bar in
a toolpost holder on the carriage, roll up to where I just start to see or hear it cut, and then watch the handwheel to cut
.116" into it (depth).  So I might be a couple thousandths shallow at this point.  Since I have rolled the carriage into the gearcase before I start to cut, there is no backlash to worry about.

As for how wide to cut, my first pass (above) I just cut away "some" to get rid of the teeth.  Then I measure the inside of the can with calipers to see how close I am to 0.335".  Then I just make a few passes, knocking off .020" at a time until I get really close, where I measure something like 0.325".  (the handwheels and my lathe at easily good enough to do that... it's .010" we're talking about).

Now, I just use the handwheel as a guide, and I graze off a few thou at a time until I can just barely get the insert into the case, and I stop there.  Usually at this point, the insert fits good, but doesn't go quite all the way in, because remember, I only
cut .116" deep (and that was a little dodgy, by eye and handwheel).  So now I just leave the boring bit right where it is because
I know the width is good, and cut a hair deeper, then test-fit the insert, and so on, until it pushes in flush, where "flush" means
I can hold a steel straight edge across it and it looks and feels good.  This is a little lax on the depth, but the motor and gearhead
can easily tolerate this.  There is a little boss on the end of each planetary that is at least .010" high, so the lateral alignment doesn't have to be any better than that.  The circular fit of the insert inside the can is the critical thing - that has to be snug so it
will be centered.

So my inserts do not press in with a "hard fit" like the original.  They fit "finger snug", and I put a few drops of green loctite on them before pushing them in for keeps.  That stuff is strong enough to keep it from ever coming out, but I could still pull it out if I really needed to.

So far, I've done 4 of these, and they are getting faster every time.  I can do one in less than 30 min now, and they all work great - all start up at under 0.3 volt, all draw the same current as a factory gearhead, and they don't make any noise.

I keep meaning to make a whole video for entertainment purposes of how I'm doing this.  I will.  I have just been too busy.

[narrowminded]

Thanks @mmagliaro.  I'm sorry if I'm being a pain in the butt about this but until I get one apart I won't have all of these dimensions, yet I want to make the puller to get it apart, before I have one apart.  The chicken and egg thing.  This is enough, I think.  You've been very helpful as always.

[metalworkertom]

That's excellent @mmagliaro .  Thank you.

I'll probably allow an 1/8" and a little bore depth to clear the thickness.  Do you have an 8mm housing sufficient for dimensions?  I'm thinking that one tool with a body grip adapter could be used for both the 10mm and 8mm gear case.  That might have the 10mm bore depth a little deeper than otherwise needed to be sure it clears on the 8mm housing.  It seems like a good idea to do this once the effort is started.  It would also have to clear the 8mm end cap flange. 

I'm curious how you're measuring the new end bore to get the new press dimension?   I might make a go/ no-go plug gauge for that.

What dimensions do you want off the 8 mm . I have one on the bench.

[narrowminded]

What dimensions do you want off the 8 mm . I have one on the bench.

What I would confirm is that the body and end flange diameter are truly 8mm.  They probably are but I've seen rounded numbers used when referencing a basic model, sometimes just a few thousandths.  It matters because I have to be sure that I will clear the flange when pulling, both depth and height (the pocket has to able to accommodate the full length of the end cap), but especially for a collet type clamp gripping the body.  That dimension by design will take up some error but has to be pretty good and also must clear the flange of the end cap to assemble to the body.  All of these are probably good to the body number but I have had to redo too many parts where the information I was working from was flawed.  A minute now can save a headache later and will assure the thing works from the first.

Also, are the 8mm guts the same as the 10mm with just a reduced body diameter?  I wouldn't be surprised either way but considered the possibility that it is the reason there is a projecting flange on the 8mm where the 10mm presses in flush with the body end.  If they are the same that will allow for the same push bar for both sizes to remove the output end flange.  That should make for a complete tool to do all that N scale folks would be interested in.

[mmagliaro]

What do you mean "same guts"?  You mean are the 10mm internal gears and planetary disks the same as the 8mm?  Definitely not.

Dimensions for 8mm gearhead:
Gearhead body OD 0.313"  (7.95 mm)
Threaded Insert flange OD (the part that hangs out the back of the gearhead)  0.311"  - yes, it is 2 thou smaller than the body
Threaded insert main OD (the part that pushes inside the gearhead body)  0.276" (and this is nominally the gearhead body inside diam)
Insert total length 0.132"
Insert flange length 0.036"

By the way, to measure there, I needed to get the insert out of an 8mm gearhead.  Since it doesn't push completely inside
like on the 10mm, my puller tool nor my screwdriver trick won't work.  I took a leap and just chucked the gearhead
body in the tailstock chuck on my lathe, screwed the M5.5 tap into the other end, into the threaded insert, and chucked the
tap in the main spindle chuck of the lathe.  Essentially, I put the gear "on the torture rack".  Then I cranked the handwheel of
the tail stock and it just pulled the two apart nice and easy.   

I bet the same approach would work with the 10mm.  Just use the lathe to pull the two apart.  As long as you put a collet
in the tailstock to evenly press on the body of the gearhead all the way around, instead of just using a plain old 3-jaw chuck
that might deform the body, this technique should work fine and it is by far the easiest way I've seen yet.

[metalworkertom]

I'm getting 7.9 mm on the gearhead body. 7.0 mm on the  female threaded insert  , 7.9  on the flange. Planatary gears are visibly smaller.