Author Topic: Compact Axle Hung Motor Gearbox  (Read 2740 times)

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Offline Peaky 556

Compact Axle Hung Motor Gearbox
« on: January 10, 2016, 08:02:08 pm »
No, I'm not going to call it a CAHMG!  I had enough of abbreviations at work...

This thread has been born out of the deliberations started by Ian T under 'AHMG', in which he set out to contrive a low-cost gearbox design to match the exciting new High Quality Seven Pole motor (there being something like 200 examples owned now by Forum members).  The gearbox would also need to fit within the bogies of diesel or electric locos. 

Two designs were spawned and developed to the point of being deemed practical under that thread.  Ian's design was further developed by ClassicDelights to use all-metal gears, and a prototype is nearing completion.  Ralph's design has been built and demonstrated, using the most cost-effective components, namely nylon gears where available. A stronger design using all Delrin gears is under development by Ralph.

My personal aims are to fit three units into the "Peak" 1-Co bogie. If this were possible then other classes using that bogie could be so powered too, eg Classes 40, 45 & 46. My knowledge of other classes with the same bogie is zero, not being on my wish list to model!  It would also fit other Bo-Bo or Co-Co bogies with wheelbase of 8' or more, provided the wheels were as big as the Peak.

The driving force behind my aim is to perpetuate the sound thinking of the late Dave Lowe, who promoted the use of AHMGs on all axles that were powered on the prototypes. His model of Kinder Scout was a great example of what could, and I now believe, should, be done.

Reviewing the space limitations imposed by this policy highlights the main difficulty; fitting these into 8' wheelbase bogies. In G3 this is a tad under 108 mm, but I'm gonna cheat and use the full 108 mm!

When I expressed an interest to Phil in taking up six of the Ian T designed AHMGs, I hadn't realised just how long they were.  Phil later confirmed that three units would definitely NOT fit into a Peak bogie.  My apologies to you Phil regarding my stated interest, which has since dropped to zero I'm afraid.

Accordingly I set about developing my own solution for my specific requirements, being the use of the HQ7P motors, cost-effective, sized to fit three within the outline of the Peak 1-Co bogie, and assuming a relatively low total power requirement for all six motors of around 80 W to get the show on the road yet still move pretty briskly.

More anon.

Regards, Tim

Offline Peaky 556

Re: Compact Axle Hung Motor Gearbox
« Reply #1 on: January 10, 2016, 08:25:20 pm »
I don't boast much original thinking in this compact design, but instead owe inspiration to a lot of people:
*Ian T for the impetus to start looking, and trial look at idlers to shrink the length,
*Ralph for the 'el cheapo' Moffett moulded gears, promotion of MOD1 for robustness, and concept of bolting the final gear to the inside of the drive wheel,
*John for making available the quality motor design to the forum members,
*Ralph again for alerting us to potential fragility of the motor with regard to overheating and the probable need to limit applied voltage to 6V,
*Phil for the concept of a split sideplate design to allow clamping of the motor,
*the late Dave Lowe for the whole concept and also use of Bowmet PTFE bushes, as demonstrated by him for great durability,
* and the good common sense, support and contributions of all those on Ian's thread.

That's enough of the gushing credits, so I'll describe some features of the design next.

Regards, Tim

Offline Peaky 556

Re: Compact Axle Hung Motor Gearbox
« Reply #2 on: January 10, 2016, 09:03:17 pm »
Mine is a single stage gearbox, siting the motor partly between the wheels as far as the motor rear bearing boss will allow, and with an idler gear used to take up the resulting space.  The final drive gear is the largest that can be fitted inside the drive wheel without contacting the railhead. The idler gear is sized to the maximum that fits inside the bogie outline, and the motor pinion is the smallest commensurate with the above.  Many combinations of motor position, idler and pinion size were assessed. Motor position was restricted by the need for a frame stretcher midway between axles, and that at one position at least in the bogie, the two motors would be adjacent.

Restraint of the gearbox is by a tab on each sideplate that locates in a horizontal slot in the frame stretchers.  Positioning of the sideplates is such that the pairs will 'nest' together where they are adjacent, and still leave room for lateral sliding of the axles on curves.

The gears are all of the cheap moulded Muffett variety, at MOD1.  A degree of thinning is required for the two bigger gears.

The sideplates are accurately spaced, use PTFE lined bushes for the drive axle and idler shaft, and are very restricted for minimal side play in order to keep the gear mesh as broad as possible.

Sideplates are thick enough at 4 mm to allow the split for clamping the motor to be clamped with an internal M2 screw.

Shafts will be silver steel, and spacers from Technobots.

I'll try and post a side elevation tomorrow.

Regards, Tim

Offline John Candy

Re: Compact Axle Hung Motor Gearbox
« Reply #3 on: January 10, 2016, 10:13:28 pm »
For the record, the 1-C0 bogie design used on the BR Type 4 diesels originated from Bulleid and first powered the three SR diesels Nos. 10201 -10203.

John.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline Peaky 556

Re: Compact Axle Hung Motor Gearbox
« Reply #4 on: January 11, 2016, 10:38:24 pm »
Thank you John, I'd forgotten them.

Sorry no illustration yet as I can't figure out how to put a CAD drawing on the forum!

Regards, Tim

Offline Peaky 556

Re: Compact Axle Hung Motor Gearbox
« Reply #5 on: January 12, 2016, 07:15:13 am »
Try this illustration as a PDF of the CAD file.
If it's legible then the green are the gears, black the structure (wheel, rail, frame stretchers etc), red the motor, and brown the gearbox sideplates.
Regards, Tim

Admin Note : See PNG image in post below.
« Last Edit: January 12, 2016, 03:03:50 pm by John Candy »

Offline cabbage

Re: Compact Axle Hung Motor Gearbox
« Reply #6 on: January 12, 2016, 07:21:10 am »
Tim,

I can't open your file. The report from Adobe is that the file type is not supported or is damaged? Try a direct pointer to URL.

regards

ralph

Offline John Candy

Re: Compact Axle Hung Motor Gearbox
« Reply #7 on: January 12, 2016, 07:46:35 am »
Tim the file you have uploaded is 0kB (i.e. empty)
The forum server is currently set to accept the following file types  doc,gif,jpg,pdf,png,txt

The file size limit is 70kB per attachment.

What file size and formats  is your CAD software capable of exporting?

If necessary, I can arrange for it to be uploaded to a directory and linked to your post (which is what Ralph has suggested).

John
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline John Candy

Re: Compact Axle Hung Motor Gearbox
« Reply #8 on: January 12, 2016, 08:27:54 am »
Here is the image referred to above.
My fellow Members, ask not what your Society can do for you, ask what you can do for your Society.

Offline cabbage

Re: Compact Axle Hung Motor Gearbox
« Reply #9 on: January 12, 2016, 12:19:28 pm »
Tim,

Stellen Sie bitte die Zahlen auf Englisch...

regards

ralph

Offline cabbage

Re: Compact Axle Hung Motor Gearbox
« Reply #10 on: January 12, 2016, 02:46:32 pm »
Personal viewpoint:

1: I think your gearbox is upside down. This is because the motor magnets will be nearest the rail -thus collecting magnetic scrap and triggering reeds.

2: At 4:1 the gear ratio is I think a little on the high side. This will affect slow speed performance and I personally like something in the 6 to 8 range. But with 7 poles this should smooth out some of the jerkiness, swings and roundabouts I suppose?

The lovely curves are laser cut rather than a tenon saw. There seems to be a transverse bar between the plates -or is this a hole to bolt the gear to the wheel?

regards

ralph

Offline Peaky 556

Re: Compact Axle Hung Motor Gearbox
« Reply #11 on: January 12, 2016, 05:37:11 pm »
Ralph,
1. Could this be because you were born in the Southern Hemisphere ?  ;)

2. Couldn't agree more, but this is the best achievable within the space constraints I imposed on myself (I like a challenge)! Way back in the early days of Ian's thread I thought the best available without an idler was even worse..

3. There is indeed a transverse spacer between plates, namely a commercial electronics-box spacer, with a M5 bolt through the middle.

Am now sourcing parts...

Regards, Tim

Offline Peaky 556

Re: Compact Axle Hung Motor Gearbox
« Reply #12 on: January 23, 2016, 04:19:03 pm »
Parts are either ordered or delivered.
I'm having awful trouble in providing a suitable file type that MEL can read.
I've offered .dxf, .dwg types, and saved as various antiquities including 2000-2002, 2009 (I think), and now with Andy's help ACAD14.
Question is what trick am I missing?
 :-\ Tim

Offline cabbage

Re: Compact Axle Hung Motor Gearbox
« Reply #13 on: January 23, 2016, 04:33:43 pm »
I have success with MEL at the following settings:

DWG R2000 Millimetres

DXF R2000 Millimetres

regards

ralph

Offline Peaky 556

Re: Compact Axle Hung Motor Gearbox
« Reply #14 on: February 21, 2016, 08:22:22 pm »
Hello all,
I was just thinking of giving an update on this compact gearbox, when I was trumped by Phil!
All credit to Phil and Ian for a lovely job, but mine is not in direct competition as it will fit within the 8' wheelbase of the Peaks.
Here is a trial assembly of the main parts, albeit unfinished.  I will carry on this week and hope to table a couple of them on Saturday.
Best regards, Tim
PS am having trouble with picture types, have PMd John.