Axle Hung Motor Gearbox (AHMG)

[Peaky 556]

Ralph,
The gear ratio is 7.2 using your stated gears of 10/60, 40/48, not 9.2, as pointed out previously!  All interesting, but what do you hope to gain from knowing torque at the driving wheel? Weight on the wheel and friction with the rail will govern the limits of loco Tractive Effort. You will also need to know rotational speeds to get the full picture. I would like to use your dyno on the motor shaft if it can be sleeved to fit, together with tachometer, to characterise that motor.  Might we do this on the E Midlands Group table at the AGM?

John,
I have another gearbox design that I shall call the Compact AHMG, but don't know whether to start a new thread, as this one has surged off on a lot of tangents.  Advice please.

Cheers, Tim

[IanT]

For my 2p Tim - the more the merrier - let's see it.

Regards,


IanT

[John Candy]

Tim,

We now have three proposals:

Ralph's , Phil Flint's and yours.

I think we need to split this topic 3-ways.

John.

[Doddy]

I think we need to split this topic 3-ways.

Why? The title says it all 'Axle Hung Motor Gearbox' The fact that there are three or more designs matters not.

Personally I find it is easier to track the development of such a project within one thread.

[John Candy]

Why? The title says it all 'Axle Hung Motor Gearbox' The fact that there are three or more designs matters not.

I will wait to see what others think but we are already on page 11 of this topic and by the time we reach "22", I think we may all be confused!

Regards,
John.

[cabbage]

I am sorry that you do not agree with my maths Tim....

10:60 first stage.
40:48 second stage.
37.5:48 third stage.

Well at the end of the test -the results may be found here:

http://www.cabbagepatchrailway.webspace.virginmedia.com/report.pdf

The coefficient of wheel to rail is normally taken as 1:4.2 or as I prefer the more useful "240grammes per kilo of loco". Why do I want to know the torque at the driving wheel -because it is the easiest method of finding the torque at the shaft.

regards

ralph

[classicdelights]

Gents

Just to update you on progress regarding Ian's design.  I now have all the parts except the laser cut gearbox frames; I am awaiting delivery on these.  I have machined up the spacers, intermediate shaft and the axles.  The gears from Muffett look superb, these are precision gears not to be confused with other types available.  We just need the remaining parts and it can all be fitted together.  I think this design will be worth waiting for, a real Rolls-Royce gearbox that should meet the needs of all electric and diesel-electric outline models.  I cannot see that the motor will not be powerful enough as 4 very cheap MFA motors did all that was required in my gauge 1 Class 40 and the ones we have for this AHMG are much bigger.

I am currently designing a Bo-Bo bogie to mount the gearbox into - all will be revealed in due course.  This design will sit down very low with most of the works contained within the bogie, I think that this characteristic is preferable and will help get all the other stuff like batteries into the loco body.

Regards

Phil

[Peaky 556]

I am sorry that you do not agree with my maths Tim....

10:60 first stage.
40:48 second stage.
37.5:48 third stage.

ralph

You are confusing me now Ralph as the mechanical engineer in me can only see two stages in your gearbox.  Also if your "third stage" had a gearwheel with 37 1/2 teeth, that would be a sight for sore eyes!
Tim

[Peaky 556]

Phil,
Greatly looking forward to seeing the "Rolls-Royce" gearbox, which should be very strong and durable with all-metal gearing. Am hoping you bring it to the AGM, and that we will have the opportunity to sit the trio of designs together. What thickness of sideplate steel have you specified, and do you have an idea of the cost and turnaround from MEL?

A design question, probably aimed at Ian, did the shaft centres correspond exactly with the half the sum of the individual gear PCDs, or is an additional allowance made for a working clearance to avoid premature gear wear?  Hope that makes sense. I'm currently assuming the former but have not built it yet.
Regards, Tim

[classicdelights]

Tim

All being well it will be at the AGM.  I have used Ian's design as he intended it so it has 3mm steel gearbox side plates.  It is all good substantial stuff.

Phil

[cabbage]

I personally am very happy with my gearbox designs being tested by Tim alongside other designs. The reason you cannot see a gear wheel of 37.5 teeth is the fact that (as we both know) I am referring to ratio of Gear 4 (48mm) to the drum (37.5mm) of the dyno. As in the test unit at Bulawayo shed it is made of two wagon wheels stuck together (rather than welded). NOT until the drum had been loaded with 12 ounces was it possible to see the white square stuck to the drum as anything other than a blur. What it has also proven is the use of nylon gears in high torque situations. I am going to order the gears for "El Mucho Macho" tomorrow. This will give a gearbox more suited for N2.5GA usage. How much torque will the Johnson 600 series develop -I don't know. The kitchen weights only tot up to 16,8,4,2,1,1/2 and 1/4 ounces... This would give a maximum brake of the drum of 31.75 oz = 0.9kg which I think a J600 series will do with ease. Using the std HG "formula" then the amount of wagons etc that EMM could be rated at as 19 x 0.9Kg = 17.1Kg PER MOTOR.

It would seem John that the R-7 transporter and M-64 c0-c0 D/E loco could be easier to build than I thought.....

regards

ralph

[IanT]

Tim,

My CAD model uses the PCDs as the intention was first to find a viable set of commercial components. If you recall, I wasn't originally too sure if things would even fit when using the HQ7P. Once satisfied with the design, I was going to build a test unit to iron out any problems. Events seem to have overtaken us but I don't think this will be a serious issue. It's always good to build a new design and see how it performs but this is what Phil is doing I believe.

By the way, my/Phil's gearbox will only be of use initially to anyone with HQ7P motors, although I'm sure a variant (that uses other motors) can be developed. Ralph's version uses freely available motors which may be useful to others. I'm not sure what motor Tim intends his 'compact' design to use and of course (lurking in the background) we also have the 'Hi-Tec' motor alternatives. For a change - G3'ers may be spoilt for choice!   

John - if you are concerned about the length of this thread - by all means hive them off into separate ones (with "AHGU" somewhere in the title?).

Regards,


IanT

PS I want my Mug to read "Gauge 3 - Where Big is Better"   

[Peaky 556]

I personally am very happy with my gearbox designs being tested by Tim alongside other designs. The reason you cannot see a gear wheel of 37.5 teeth is the fact that (as we both know) I am referring to ratio of Gear 4 (48mm) to the drum (37.5mm) of the dyno.
ralph

Ralph,
I have no desire to test your gearboxes; it was use of your brake to test the HQ7P motor that I was suggesting, ie the motor with a brake on its shaft, if that can be contrived?
Re the gearing confusion, I know that the radius of the drum brake (plus radius of the string being used) needs to feature in the calculation of torque, however to refer to it as a further 'stage' in the gearbox, and calculate a reduction ratio of 9.2, is misleading...  I assume that you are using a spring balance in the rope between its fixed point and the drum, so that the true tension incurred in the rope by the pull of the brake is being measured? Does your column of torque figures refer to torque at the driving wheel or torque deduced at the motor shaft? If the former you wouldn't even need to mention the gearbox ratios, so am I correct to assume it is motor output torque?

Ian,
I'm sticking with the HQ7P motor for now, for two reasons:
1. I've bought a bunch of them!
2. The other motor that Ralph is acknowledging, the Johnson 600 series, seem to be considerably larger if those in my scrap motor box pictured are from that stable ( I may be wrong!).

Regards, Tim
PS, sorry, cannot get picture small enough to post...

[IanT]

Yes, I've got a few too Tim!



Regards,


IanT

[cabbage]

The gears have been ordered from Muffet:

S1.0 012H    £1.10 ea

S1.0 040H    £1.85 ea

S1.0 048H    £2.20 ea

S1.0 060H    £2.99 ea

P+P is £4 1st class -which is quite reasonable. The whole lot is also plus VAT. The J600 motors are off eBay at £11 for three(?) 8mm PTFE lined steel bushes are 59p each. So to build one EMM would cost :

Gears £8.14p
J600  £3.66p
PTFE  £1.18p

=£12.98

I will use PolyCarb for the plates as before.

regards

ralph