Axle Hung Motor Gearbox (AHMG)

[classicdelights]

Gents

Some pictures of the AHMG in a typical Bo-Bo bogie, this one will be for a SR Electro-Diesel for marshalling coaching stock around when the layout gets built.  It is a pity that Ralph does not like anything anyone else does but you cannot please all the people all of the time.

Phil

[Peaky 556]

John,

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.

regards

ralph

Ralph,
I do admit that I struggle to understand the relevance of your torque numbers, but maybe I am thick?
You particularly confuse me with your units.
When you say the "motor" develops that much torque, I suspect you mean the gearbox output shaft to the driving wheels gives the 2778 gcm?
The next matter is how to apply this to a 5cm wheel. I think you are deducing the force available at the wheel perimeter, which will become 2778/2.5 = 1111g, or around 1.1 kgf.  this represents the maximum Tractive Effort I believe from one axle being driven by your AHMG, assuming enough weight to prevent wheelslip. No more calcs are necessary, so what is the 40kgM (which is a huge torque)?
Tim

[cabbage]

Tim,

I am a child raised on Centimetre Gramme Seconds. Yes the torque quoted (2,788gcm) is the torque at the output of the two glued together wheels that formed the "drum" of my brake dyno. The 40KgM is a typo, should read 240gcm assuming 1:4.3 limiting friction. I had been busy all day building a guitar and I have just now finished cleaning up afterwards.

Phil,

I am very easy to please... But what I abhor is waste. If I was going to buy this gearbox I would have to ask myself -is this good value for money? To me the answer would have to be no. To power "Ixion" I would have needed 6 of them. Thus the cost breakdown would have been over £800 in gearboxes alone. This is TWICE the cost price of my new Churchill Conquest Lathe which I bought last year.... Or to put it in more basic terms that is about the same money as I spend in ASDA on food over 4 months.

If you can produce this as a marketable product with a suitable robust motor in the £30 to £40 bracket I will willingly applaud you.

But as it stands -I have to say this is snark hunting....

regards

ralph

[classicdelights]

Ralph

I have no interest in producing this at all.  I asked for a straw poll and there was no significant interest so I decided to build what Ian had designed so members could see it.  I am prepared to write up a construction article for the Newsletter so members can have a go themselves if they wish.

Personally I think Ian's design is a good one, it is you who has missed the point, Ian designed a gearbox to go with the 7-pole motor that had been made available to members cheaply and could be used in more or less any diesel-electric type model, it was not a design for any motor you might want to fit.

Phil

[Peaky 556]

Yes the torque quoted (2,788gcm) is the torque at the output of the two glued together wheels that formed the "drum" of my brake dyno. The 40KgM is a typo, should read 240gcm assuming 1:4.3 limiting friction.
ralph

Ralph
I'm still trying to pick the pieces of information out of your treatise on torque that is relevant to the real world!
I think John's question about torque output is answered by your figure of 2778gcm.  However that is a fairly useless figure to predict performance on the track as there will be dependencies on wheel diameter, weight on the axle and speed of rotation.  Hence my calculation of the theoretical maximum tractive effort of around 1.1 kg.  This much will not be achieved in practice as wheel slip will occur unless there is a weight of over 4.7 kg sitting on that axle (being highly unlikely).  I believe you are mixing up the mechanical fundamentals though, by saying the torque reduces to 240gcm as a result of limiting friction at the rail.  The torque available at the wheel will be unchanged, the figure that IS changed is the tractive effort because of the friction, NOT the torque.

I also have to ask John for more clarity on the questions, as the same ones are asked of my compact AHMG!

Regards, Tim

[IanT]

 "IanT - You have failed to read what was written...."

Ralph, it might be useful if you took your own advice.  I've already pointed out that Phil has given the cost of one gearbox as £67.45 - half the amount you've quoted in your recent critique of Phil's gearbox. The cost of six units would therefore be £404.70 (not £800) and whilst this is still a goodly chunk of money, when compared (for example) with an ABC Gears (Gauge 1) Traction Unit at £77.00 (six units = £462) then it doesn't sound quite so bad by comparison. This is also before any further development work has been undertaken to refine & evolve the design.

I still intend work on my own AHMG designs, partly for the entertainment but also because some of my engines may need specific features. I've already stated that it's not at the top of my priority list at the moment and frankly since Phil, Tim and you have all produced (what certainly look like) viable G3 traction units for anyone that might need one – then that also decreases any urgency in my view.

However, I'm certainly looking forward to having a closer look at all the units present at the AGM and I'm sure there will be much to learn from them, which I will be perfectly delighted to pinch use in any future designs of my own.

In the meantime, it seems to me that another small part of the G3 "problem" (e.g. "You can't get those in G3") has at least been partially addressed and I'm sure further progress can be made over time. So I'd much prefer to focus on the very positive aspects of these efforts and to congratulate & encourage all of those (including you Ralph) who've made the effort to move us forward in this area in such a relatively short time.

Regards,

IanT

[cabbage]

Tim,

Your definition of torque -I term as SHAFT torque. Thus the shaft torque from the gearbox motor combination is 2,778gcm. The RAIL HEAD torque is the torque available at the rail to wheel interface which should be 240gcm per kilogramme of down force at the interface.

Thus there is ample shaft torque to spin the wheels on an axle -or drive more than one set of axles.

Maude (2-D0-2) uses one motor driving 4 axles via offset chain link from her simple, (12:1), 2 stage gearbox. The shaft  torque out of the motor gearbox on Maude is probably an insanely high figure for a G3 model. But it allows her to pull long trains at high speed -which she was originally designed for.

It is almost the reverse of your method. I have 5 power axles, the model weighs in at 10 kg. Thus the maximum torque to the rail head I can put through each axle is 480gcm. The gearbox motor needs to develop a shaft torque of 2,400gcm. Given the figures above at 2,788gcm the "el cheapo" gearbox with its 60p bin hair drier motor -will do the job....

regards

ralph

Post Scriptumn: IanT my reading is correct. Ixion has 12 motors and 12 gearbox assemblies with one motor gearbox at each end of the driving axle -thus ensuring perfect balance.

[John Candy]

I have been asked (by the motor supplier) whether anyone on here would be interested in developing a double-motored gearbox.

I will quote what has been asked:-
...... I will discuss the mating of two motors facing each other, one running CW and the other CCW through the worm. ....... do you know of any member who would undertake this task ?

I am not going to comment or pass judgement on the advantages or disadvantages of such an arrangement but it would give double the "grunt" for the price of a single gearbox.

John.

[IanT]

I can't say the idea really appeals to me John but nor am I planning anything quite as ambitious as Ralph's twelve-motor "Ixion".

I'm afraid that I can't resist mentioning that the 'Ixion' (of Greek mythology) killed his father-in-law by pushing him into burning coals and eventually went completely bonkers. He also upset Zeus just a trifle, who bound him to a fiery wheel to spin for all eternity. Unfortunately there is no record of exactly how many motors Zeus used to power his wheel.



IanT 

[Peaky 556]

I have been asked (by the motor supplier) whether anyone on here would be interested in developing a double-motored gearbox.
I will quote what has been asked:-
...... I will discuss the mating of two motors facing each other, one running CW and the other CCW through the worm. ....... do you know of any member who would undertake this task ?

I am not going to comment or pass judgement on the advantages or disadvantages of such an arrangement but it would give double the "grunt" for the price of a single gearbox.
John.

AAAAAAARGHHHH!
Pardon me whilst I go to dunk my head in a frozen water butt..
?

[Doddy]

It seems to me that another small part of the G3 "problem" (e.g. "You can't get those in G3") has at least been partially addressed

I am not so sure that I agree with his statement. These are not 'available' they are merely test mock-ups of different designers requirements in operational usage and their respective budgets.

I'm sure there will be much to learn from them, which I will be perfectly delighted to pinch use in any future designs of my own. I'm sure further progress can be made over time

I think this belies the truth that when the word 'pinching' is used as the vernacular then you know that further development of certain designs can only be furthered by their own respective designers.

The advice I received was that all the information for creating one of these designs, was that the information required was in the forums postings (which it is not).

So, I am going to take the forums contributors advice and bugger off and do it myself.

[Peaky 556]

Bob,
Can I suggest that you ask publicly on this forum for whatever information it is that you require?
The impression given is that some private correspondence is not to your liking, but without the detail.
All of this leaves rather a bad flavour on what has been a very constructive series in my view, and we should be encouraging healthy development of these prototypes, with an eye on a possible commercial uptake for those who cannot engineer them them selves.
Tim

[MikeWilliams]

For the benefit of those like me who have dipped in and out of this topic and following IanT's comment about plugging a G3 gap, is this a reasonable summary?

- We have two very promising designs of gearbox ready to test.
- Both use entirely commercial parts except some frames and spacers.
- Neither is dreadfully expensive (you can argue about "dreadful" if you wish.
- If a manufacturer invested in those frames and spacers and instructions, most modellers would be able to make a workable unit.
- It would not be hard to make a batch of gearboxes ready assembled.

If that is the position then we have indeed almost plugged a gap.

Mike

[cabbage]

John,

An opposed double motored worm gearbox -I have already done one! They power my Klein Lindener loco at 16mm scale. The problem is more to do with vibration and the fact that you really do need a worm with at last two "starts". Worms are also very lossy in terms of friction although very good reduction ratios are easily possible. A Simple MOD1 worm and spur setup can produce 20:1 with no real constructional problems.

regards

ralph

[John Candy]

Ralph,

Thank you for that input....any chance of a photo. of the two-motor unit?
I will pass your advice on to the chap who is looking at possibilities.

Regards,
John.