Axle Hung Motor Gearbox (AHMG)

[John Candy]

Thank you for the offer John -But I would prefer it to be a LOAN!

....and I thought I would be able to clear a spot on a shelf!
OK Ralph, if you insist.
I will post within a couple of days.

Regards,
John.

[Peaky 556]

John,
Before you post one, could you kindly measure up the OD of the motor body where the clamp plates might sit, as I have variously seen both 28 and 29 mm quoted on this thread? Indicating calliper dimensions to the nearest 1/10 mm will do!
Thanks,
Tim

[John Candy]

Diameter over metal casing 28.62mm
Diameter over (plastic) shaft bearing housing 16.80mm
John.

[cabbage]

Ok here are the gear plates -a little rough and ready but nothing that a little care and attention will not improve!

The first shot shows my "victim" a old off cut of A4 size 6mm poly carb that was bought to build the three 4-stage gearboxes that power "Lady Jane Gray". You have to be very careful and SLOW when using polycarb. Otherwise the heat generated by the cutting action melts the polycarb and embeds your teeth in the pieces....

http://www.cabbagepatchrailway.webspace.virginmedia.com/plates1.jpg

Using my Dads tenon saw, (I needed the very coarse teeth), I cut out the two 75mm square pieces needed.

http://www.cabbagepatchrailway.webspace.virginmedia.com/plates2.jpg

A couple of more SLOW cuts produced the basic "L" shape of the plates.

http://www.cabbagepatchrailway.webspace.virginmedia.com/plates3.jpg

After having scratched "the datum line" on one of the pieces I clamped them both together and began co-ordinate drilling with a wheel brace.

http://www.cabbagepatchrailway.webspace.virginmedia.com/plates4.jpg

The rear plate  had its "Axle Hole" tapped to M4. The M4 bolt will act as both spacer and axle for gears 2 and 3.

http://www.cabbagepatchrailway.webspace.virginmedia.com/plates5.jpg

The holes for the motor to slip through were cut from my collection of "spoons" using a hand brace.  The rear plate has a 28mm hole and the front one an 18mm hole. These being the nearest I had to the desired sizes. Some work with a file and sand paper required once I have a pukkha motor to fit.

http://www.cabbagepatchrailway.webspace.virginmedia.com/plates6.jpg

The edges will get "rounded off" and everything "prettified" later. It has taken me circa 90 minutes to do these. If I had used plate steel then it would have been faster as I could have unlimbered the mill  fabricator etc in the shed.

regards

ralph

[cabbage]

Phil asked "how long until we see something in print" -he got a draft drawing in under 6 hours.
Phil said "Perhaps we will have two different gearboxes to see at the AGM!" -he got a "statement of intent" to a working "pre-production prototype" in under 24 hours.

http://www.cabbagepatchrailway.webspace.virginmedia.com/plastic%20gearbox.MP4

it is 10 seconds long and a 4.4Mb download.

Time for a cup of tea and cheese+onion sandwich!

regards

ralph

Post Scriptumn: sometimes it is nice to prove that although I am retired the mental skills are still there.

[John Candy]

That looks very good Ralph.
You should have your motor tomorrow, if the Royal Mail "does its stuff".

Regards,
John.

[cabbage]

That is the "El Cheapo" version! By replacing the Nylon Gears 1,2 and 3 with steel (1), and Delrin  (2+3) respectively it could be developed into "El Much Macho" which would be more suited to N2.5GA work. I have to go into town in Friday anyway so I will see if I can get a more "suitable" motor for that use. The reason why there is a steel primary gear in "El Mucho Macho" is that I can get them with just a pilot hole and drill them to the required shaft diameter -which is 6.4mm(!)

If time allows, (I am busy with "Southern Magyar" getting it ready for the G3S AGM), I will try and built "El Mucho Macho". It should not cost more than £15 anyway! Any G3S member that is also a N2.5GA may take it away for "track evaluation" -but I do want it back again!!! I have an idea for a N2.5GA loco that is a B0-B0 -the Rjukan No.14. I could NEVER get this thing on my track, (it corners like a brick)....

regards

ralph

[cabbage]

I have the pukkha motor now. Having looked at how it really is "in the flesh" I am going to enlarge the hole for the motor in the motor plate so that the hole is the same size as the one in the rear plate -in short make the two identical. I can mount the motor radially by compression fitting on both plates.



The next shot shows how it would sit in rear life (the wheel was the first one to hand!)



As you can see a dead easy design for you to play with.

regards

ralph

[Peaky 556]

That is the "El Cheapo" version! By replacing the Nylon Gears 1,2 and 3 with steel (1), and Delrin  (2+3) respectively it could be developed into "El Much Macho" which would be more suited to N2.5GA work.
ralph

Very interesting Ralph, and it's great to see it virtually in the flesh.  Also an interesting comment about the materials, so in your experience is the Delrin (ie the white Muffet 'Hostaform') stronger or more durable than the red nylon of the Technobots gears?

Regards, Tim

[cabbage]

The Red nylon gears as supplied by Technobots are quite capable of taking up to 10W motors. The £2 Johnson 600 series Motor that will power EL Much Macho is around 35W. The teeth of the white Delrin gears are 9mm wide and sit on a far deeper rim than the Nylon ones. Delrin is far stronger than Nylon but has the added problem of being almost impossible to "stick" things to it due to its condensation polymer formation. Mechanical fixing is required for practically everything -you cannot "threadlock" the grub screws for instance.

As I said the "El Cheapo" is a G3 design whilst "El Mucho Macho" is more towards the N2.5GA arena. If you are worried about wear and tear from just Nylon gears -both "Maude" and "Rosebud" both run on Technobots Nylon gears with Johnson 600 series motors. Maude, as you know, is capable of very high speed runs!!!!

The reason that the Gear 4 is a white Delrin gear is that there is no Nylon gear of the correct tooth size in the Technobots range. A 3 feet 7 inch wheel requires a MOD1 48T gear wheel whilst a 3 feet 9 inch wheel can use a MOD1 50T gear wheel -which DOES exist in the Technobots range (and is cheaper than the 48T!)

So -if you have "freight wheels", then Gear 4 more than likely has to be Delrin -anything bigger there is probably a Nylon gear that will fit your requirements.

regards

ralph

[Peaky 556]

Thank you for advice on the materials Ralph. My temptation is to use Delrin all round.

Just a word of caution to anyone else thinking of using Ralph's "El cheapo" gearbox design with a 48 tooth final gear. The diameter of this is 50 mm according to the Muffet website, which equates to 3' 8 1/2", so for obvious reasons you cannot fit this to a scale 3' 7" wheel.  It would, however, be fine for the wheels on a Peak of 3'9".  Take nothing for granted and always check against your own requirements!

Regards, Tim

[cabbage]

Tim,
You have forgotten that Gear 4 fits on the INSIDE of the wheel. Thus the diameter of the 3 feet 7inches wheel is 48.3mm plus 4mm for the flange which equates to 52.3mm. Those using 2.3mm flanges regardless, (as I do), then the diameter of the wheel is 52.9mm.

The only problem you might encounter is a set of points where the frog point to wing rails gap is far too long and the wheel drops into the gap. Then the wheel could ride on the teeth of the wheel for a few millimetres rather than the flange tip as it should.

I use 8mm wide wheels 2.3mm flanges and all my points sets are handmade from Cliff Barker kits. I have never found this to be a problem.

But your point is well taken that the MOD1 48T gear is larger than the external root of the wheel.

viz:



Wheel shown is 48.3mm plus 2mm flange = 52.3mm dia

regards

ralph

[Peaky 556]

Ralph,
You seem to be asserting that a part of the locomotive can hang below the level of the railhead, in this case the gearwheel affixed to the inside of the drive wheel.

I'm sorry but that is ABSOLUTE TOSH! (Admin's note : Let's not get too worked up over this......keep it polite and be grateful that Ralph is putting so much effort into this ..... he posted at around 3AM and may not have been "at his best").

If you are still in doubt about this, then think what happens when the gear teeth encounter the switch rails and wing rails; the loco would be caused to climb in a most ungainly manner.  The only situation that would be permissible is where there is no pointwork on the track, such as I believe is common with raised 'leg dangler' N2.5G.

And therefore no, I had not forgotten about the flange, it's just that the flange size has no bearing on this particular FUNDAMENTAL principle.

Regards, Tim

[cabbage]

Well at my best or not...

Here is "el cheapo" in operation -it has been fed off the back of a 6V SLA.

http://www.cabbagepatchrailway.webspace.virginmedia.com/el cheapo.MP4

It is definitely going to need an ESC!!!

I am going to dose up with pain killers and collapse on my sofa!

regards

ralph

[cabbage]

Ok I have run the battery flat, (it was nearly dead anyway!), but "el cheapo" has run for over 30 minutes and here are a few notes and thoughts.

The motor can be held by two M4 grub screws radially compressing the steel body (but don't try winding too hard).

The motor does get hot, (43C), after a few minutes -but that seems to be as hot as it gets. After the end of the test it was still 43C. This would seem to be "Thermal Equilibrium" for this motor. As all the running was done "no load" I don't know how hot it would get under load?

The rear power connections are 2.5mm "pits". Unfortunately these are in a plastic surround. I have "butchered" a MOLEX connector and soldered the spears into the pits to give a permanent connection, (sorry John -but it had to be done!).

The gearbox is noisy due mostly to the fact that the gears are "Rattling on their Axles" -which are in fact just a length of M4 threaded rod and a similar length of M8 rod respectively.

regards

ralph