hardest plastic for joining axles?

[nscaleSPF2]

I've been waiting for a chance to share this discovery.

Henkel, the company that makes Loctite, has recently(?) released products called "retaining compounds".  These are not your father's thread lockers.  They are designed  to attach collars and bearings to rotating shafts.  They come in different strengths, and  for different clearances, including loose fits.

I used this one to attach an acetal NWSL coupling onto a 1.5mm motor shaft.  The bond was instant, and permanent.
http://www.henkelna.com/industrial/product-search-1554.htm?nodeid=8797927964673

This stuff is pricey, about $20 for a 2oz bottle, but that's a lifetime supply for most of us.  Got mine at the local Fastenal store.

This has not been a paid commercial announcement, even though it sounds like it.

[peteski]

is there possibly room enough for a flywheel
using flywheel as the connector
each of the shafts fitting 1/2 way in
pressure fit

just thinking out loud of other possibilities
fwiw....

sincerely--
Gary

Flywheel on the driver's axle will not be very effective (or should I say not effective at all) due to its relatively slow rotational speed.  That is why flywheels are installed on the motor shafts (which are the fastest spinning parts of the mechanism).

[nkalanaga]

But, maybe, a sound cam would work as a joiner.  On the other hand, one only needs one cam per engine, so that won't be much help.

[rrjim1]

I would use Acetal joiners and Loctite 620 retaining compound if I want to later remove them or 680 if I want them to stay forever. You can purchase a small sample tube of Loctite from Mcmaster-Carr.
I have used this method for securing small plastic gears on metal shafts and it works great.

[Lemosteam]

Max, can you share a cross section of what you are trying to develop or would that give away too much of the design?

[Ed Kapuscinski]

is there possibly room enough for a flywheel
using flywheel as the connector
each of the shafts fitting 1/2 way in
pressure fit

just thinking out loud of other possibilities
fwiw....

sincerely--
Gary

Not being an engineer, I gotta say, that sounds pretty cool.

[mmagliaro]

All,

I don't have any drawing of exactly how this will all look because I haven't developed such a thing.
Basically, I plan to sandwich two brass plates together, bore and drill some screws and pins between them
so they will stay perfectly aligned after they are separated and then screwed back together,
and put some plastic spacers between them, thus forming your basic split frame loco chassis.

Next, I will put them together, mark, and mill out the 3 channels for the bearings for the 3 driver axles.

The drivers are going to have steel (or brass) half-axles, which will be joined together in the center
by plastic axle tubes.  One driver will be a tube with a gear on it, which most likely come from a Kato
Mikado (because the GS4 tubes are crap, and those gears are too large in diameter to fit
behind a small switcher 51" driver anyway).

Once I have 3 drivers, axles, tubes, bearings all located into the frame halves and rolling smoothly,
I'll figure out how I want to mount my motor in there, which will be a Faulhaber 8mm + a 4:1 gearhead.
I have already scoped out the boiler dimensions enough to be certain that there will be plenty
of room in there for that motor/gearhead combo.

The other 2 drivers will be propelled around by the rods only.

The Kato axle gear is 24 tooth, so with a 4:1 gearhead, I will have a 96:1 reduction ratio, which should be
adequate.  Allowing for a 12,000 rpm top motor speed, that gets me 125 rpm on the drivers.
At 51" diameter, we have .00252 mi/rev.  So at 125 rpm, we get a top speed of about 19 mph,
and that suits me just fine for a switcher.

But... it will go faster than that.  It's only a 3v motor, which can easily be driven to more like 5v so the
top speed will likely be in the 30's.

--------------
This is all I have throught through so far, and most of it has nothing to do with the axle tubes.

[wazzou]

Are you making an L-9?

[mmagliaro]

Are you making an L-9?

Almost... I am making the SP&S variant off the NP L-9, so they are almost identical.

It was not my intention to be secretive about that.   I just wanted to focus on this one narrow issue,
so I kept the engine discussion out of it.

When I get to actually building the engine,
I will start a separate project thread on it.    You know me.  When I build an engine, I am always so
tight-lipped about the step-by-step process....   

[mmagliaro]

Okay, so I found the Loctite 620 and 680 retaining compounds - a little pricey, but not awful.
About $12 for a small bottle.

I will experiment with some 680.  None of these is recommended for use on plastics, but then,
they always say that and the stuff is usually fine... but it doens't hold like it does on metals,
so I'm not sure I believe this is going to work in a plastic axle tube.  We'll know soon enough.

The 635 was very attractive because it has a long cure time, so that would give me more leeway
to fuss with the quartering before it sets up.  But the 680 still has a curing time high enough to manage.

[wazzou]

Almost... I am making the SP&S variant off the NP L-9, so they are almost identical.

Make 2.   

[havingfuntoo]

Max have you considered extruded resin rod used in some engineering projects that require resistance to chemicals. These materials are extremely strong and can be worked with tools that you use for working metal. The only down side is that the material is a little brittle. Provided you don't force the tools when working it you will have no problems. When working it just wear one of those painters masks and some safety glasses to protect you from the dust.
   

[rrjim1]

Okay, so I found the Loctite 620 and 680 retaining compounds - a little pricey, but not awful.
About $12 for a small bottle.

 

I designed and manufactured HO slot car parts for years, JW'S HO Speed Parts. I sold the company and retired. I manufactured Acetal crown gears for the old Aurora cars. Used 620 or 680 to hold the gear onto a smooth axles. If you wanted to remove a gear held with 680 you needed a good gear pulled or wheel press. Everything needs to be very clean and free from any oil for it to work.   

[Lemosteam]

The drivers are going to have steel (or brass) half-axles, which will be joined together in the center
by plastic axle tubes.  One driver will be a tube with a gear on it, which most likely come from a Kato
Mikado (because the GS4 tubes are crap, and those gears are too large in diameter to fit
behind a small switcher 51" driver anyway).

Max, I would not use brass axles- going into the driver. One small drop of that loco onto a driver and the axle will bend.

does this represent the design?


For the driven axle, why not press the drivers onto that great Kato 8 sided axle shaft as is?  Slide the bearing over the shaft and press on the driver. That shaft will deform the soft brass and at least on that axle you would never have quartering issues.  IIRC, when I measured that axle for my L1 build on the A-forum, the distance across the apexs was 1.8mm.  you would need a bearing with that id.

[mmagliaro]

John,
Yes, I've already been cautioned about the axle possibly bending if the engine were dropped.
I find it hard to imagine a 1.5mm thick brass rod bending under such slight jarring, but I supposed it could happen.

If the LocTite holds well on a steel axle with a Delrin tube, I will stick to my original plan.

As for pressing that 8-sided thing into my wheels, no, I don't want to risk that.  My hand-made wheel is pretty strong,
but the hub is only bored for 1.5mm and I am afraid that forcing an octogonal shape into it
will cause the thin brass spokes to bend, a solder joint to break, or maybe just push the whole wheel rim outward
non-uniformly so it is no longer centered around the hub.  None of that disaster is worth the risk.
A metal axle in a brass hub with red loctite on it is mighty strong.  I'm not worried about that end.

I was only concerned about the axle in the plastic tube side of things because of the slippery plastic.

And yes, your drawing pretty accurately depicts plan.