Axle Hung Motor Gearbox (AHMG)

[Peaky 556]

Ralph,
By using the Johnson 600 motors, aren't you giving yourself an extra headache to fit the job into a G3 bogie, as these motors are 65mm body length?   That's 15mm longer than the HQ7P!

When you come to cost the parts for your design of AHMG, I guess it would be fair to factor in the cost of all components, eg shafts, any spacers etc too. I think you also forgot to add the VAT on the gears, but I can see why adding postage cost is not really appropriate.

I am a bit surprised there are only two bearings in your design. 

Regards, Tim

[cabbage]

Tim,

Only the output shaft (the one with the rail wheel) has a "bearing". This I envisaged to be simple length of 8mm bore brass pipe. The motor has only the internal bushes/bearings the Gears 2+3 rotate on their back to back bosses. In EC this is 11+11mm of brass and in EMM this is 18+18mm of delrin. Both of these rotate on "studs" which for demonstration and simplicity I have used M4 and M8 threaded bar. A more refined one would use 4mm brass rod and 8mm brass rod tapped for the required thread and the gears would run on "plain metal" bearings, (as such).

I have a (commercially trained) habit of costing the VAT at the end of the list. I did say at the end of the list of gears that all of this was plus VAT. I have also not stated the price reduction for bulk orders -as I have ordered more than one set of them. I added postage to my pricing list because if you note the cost of postage, it is nearly 50% of the cost of one of the gear sets. It would be the same if you bought one set or the number of gear sets that I bought. The next shipping "price break" would be £7....

I have, (I admit), not costed the plates. As these are going to be "see it all move" items I am using polycarbonate. This is far more expensive than 3mm BMS sheet. I have ordered an A4 sheet at £4. As to the cost of nuts and bolts -I buy a "big bag" from the "all you can stuff in it" nuts and bolts counter at Wilkos -so they are roughly £2.99 per kilo!

Like most children I had an advanced qualification in bag stuffing before the age of 7 -as this is how sweets were sold at Bulawayo market...

The bogie is 2-co-2. It is at this point several close friends scream with laughter and say; "We have been waiting for this!!!"

regards

ralph

[cabbage]

Well a slow day after the heated work yesterday. (My hands still hurt!). So, I returned to a cooler project....

The shot below shows the gearboxes "El Cheapo" (left) and "El Mucho Macho" (right).



They will be on the E.Midlands stand at the AGM. Feel free to pick them up and fiddle!!!

regards

ralph

[Peaky 556]

On the EMM gearbox Ralph, what is your recommended way of sleeving the small pinion to fit the motor shaft?
The pinion bore is 8mm I believe, and the shaft only 1/8"?
Regards, Tim

[Peaky 556]

Sorry, I meant the pinion bore is 4mm.
As a supplementary question, with the shaft only about 1/8", is this a little small for drilling for a pin?
Tim

[cabbage]

Tim, the shaft is hard steel. I don't think you could drill a pin hole without special metal drills. I clamp the shaft with grub screws at opposing sides.

regards

ralph

[classicdelights]

Gents

The first 2 gearboxes have now been made to the final design that has evolved from Ian's initial drawings.  I have photographed one for members' information and the second is being incorporated into a trial Bo-Bo type bogie.  Both will be available to view at the AGM next weekend.

3 Pictures are attached.

As to the cost, I purchased everything necessary so that nothing came out of materials to hand or the scrap box, I wanted to know exactly what these AHMG units would cost. 

This is the cost to build 2 motor/gearbox units, I cannot imagine anyone would want just one:

Bearings   £9.35
Bearings   £6.23
Steel & Brass round (8mm & 6mm)   £9.40
Gears   £84.67
Nuts & Bolts   £2.50
Grub Screws   £0.99
6 & 8 mm ID brass tube   £9.45
Gearbox Frames (4)   £12.32
   
Total:   £134.91 including postage to obtain the parts.

I think this is what would be expected for a Rolls-Royce version of a AHMG using precision gears that will last a lifetime.  The first Bo-Bo bogie is complete and the initial sprayed coat of paint is now drying, hopefully that will be complete tomorrow.

This AHMG is not specific to loco type, any size wheels down to about a scale 3' 1" can be accommodated (just).  Hopefully members will take this design which Ian has skilfully worked out for us as a standard Society Diesel Electric Power Unit.

There is a bit of model engineering required to build one and I have done a series of pictures of the build.  These can form the basis of a construction article for the Newsletter if members are interested.

Hope to meet many of you at the weekend.

Kind Regards

Phil

[MikeWilliams]

That is a lovely looking job Tim.  And usually, if it looks right it is right.  Very nice.

Mike

[Peaky 556]

Phil
A very nice job.  As you say, it should last a lifetime.  I look forward to seeing it on Saturday.
I'll post some pics of my progress on the compact unit in a minute, but the engineering is not as substantial as on yours.  Well done 
Regards, Tim

[IanT]

Hi Phil,

Only just seen your latest photos (sorry not been too well recently)

Thank you for your acknowledgement but my design was far from finished and you've clearly had to do a lot of work to sort out the remaining issues. Your gearbox certainly looks very well engineered (and it's affordable). I am very much looking forward to seeing them at the AGM.

As another thought, I also think that this (the AHMG) is a great example of what a few determined enthusiasts can achieve when they decide to put their minds to it. Well done everyone - I'm sure there is more to come - both with the AHMG and other areas of interest.

Regards,

IanT

[cabbage]

Am I the only one here that thinks this is terrible...

The motor as supplied costs £0.60p (from my local electrical spares shop).

The gearbox designed to use the above motor costs £134.91p.

Ignoring the fact that the gearbox is 224.85 times more expensive than the motor, this gearbox can only use one specific motor. Once sources of supply of that motor are exhausted then the design is redundant. If the motor fails then the design is redundant.

If the gearbox had a removable mounting plate that could be easily replaced and custom cut for other motors then it might be "worth a punt". The turntable industry used the same technique. My Dunlop III is still going strong and I bought it in 1982 -replacing the arm boards for differing arms as required.

Yes -it is very pretty, lovingly crafted, designed. But it is not what we want....

regards

ralph

[John Candy]

Phil,
It certainly looks a "beefy" set up and should last well in arduous conditions but does work out rather expensive.......especially when 4 or more are required to power an "express" loco.

Will be interesting to know how much torque it produces at 12V (and the current draw and casing temperature  under sustained load) as well as top speed with a typical size wheel (say, c. 47mm dia.) and the "stall" current (for cut-out/fuse setting purposes).

Regards,
John.

[IanT]

Ralph,

The gearbox (as currently spec'd) costs £67.45 - which is about what I'd expect using these particular gears. Comparing the cost of the gearbox to the motor isn't entirely fair either, as when sold "commercially" they were an order of magnitude more expensive. I don't know what motors you can get from your local supplier for 60p but when I've looked for quality motors in the past, good ones have always cost more.

As for being designed to use the one motor (HQ7P) - well yes. I have a few of them (as do other members) so they are certainly what I'd prefer to use at this time. None of this is preventing anyone else from designing a different or cheaper or more adaptable gearbox (with their choice of motor, gears and optional extras) so I don't see a problem really - the more the merrier.

However, as far as I'm concerned - many thanks to Tim & Phil for actually doing what they have done. It's possible that both these designs will evolve over time but that can only happen if someone actually makes the effort and provides a starting point.

Regards,

IanT

[cabbage]

Ian T,

You have failed to read what was written....

The HQ7P motor is for sale in the 60p bin at RF POTTS ltd, Babington Lane, Derby. Photographic proof is available if required -please quote : folder BBY 9, IMG-20160108-00613.jpg if required.

We all have favourite motors I admit -mine is the SME 1502 (which is an italian made drinks vending machine pump motor) or the Johnson 600 Series (an electric drill motor) for 90p and £2 respectively. Either of which I would deem to be more suitable for electric traction than one from a portable hair drier....

regards

ralph

[cabbage]

John,

I would hesitate to use this motor at 12V for sustained periods. Using it in series from a 12V supply I would be workable. As to torque... If you re-read the results table as produced using cheap plastic gears (above) then at 16ounces of braking the motor developed 2,778 Gramme Centimetres of torque (for ease of maths) assuming a 5cm wheel would be roughly 1,000 Gramme Centimetres or 40KgM at the rail head.

As to fusing the motor -use a 3 ampere "slow blow". Thermal cutouts are all very well and good -but they are inherently unwise is a model situation. A fuse blows -the model dies DEAD and is safe that way.

regards

ralph