Axle Hung Motor Gearbox (AHMG)

[classicdelights]

Gents

I have been having a look at Ian's design with my project co-collaborator Dan, http://www.unionsteammodels.co.uk/
You can find Dan's forum from the above page.  We are looking into the viability of making up some gearbox units but require some information first.  Question No.1 is - has anyone tried the 7 pole motor out as yet and if so do you know what its RPM is under load at say 12 volts?  This is fairly crucial to getting the gear ratio about right.

We also really need a straw poll on how many gearboxes are needed.  The slightly disappointing first discovery is that the gears Ian has specified from Muffett actually cost £33.95 for a set of 4.  I don't know where we got the idea that Muffett gaers were cheap.  Dan and I will look at alternatives to bring the cost down as something in the region of £135 for gears alone if 4 gearboxes are needed for the average diesel/electric loco is not going to be very cost effective and somewhat negates the £2.50 motors.

So for a start, we need to know how fast the motor turns and roughly how many gearbox units are required if we can get the cost to a reasonable figure.

All the best

Phil

[John Candy]

Phil.

The spec given for the motor is as follows:-

Specification of "Powermaster" motor.

10.000 RPM without load.

Idle drain at 12volt is 250mAh, without load.

7 Pole.

Drive shaft diam 4mm.

Outer case diameter 28mm.

Length of case 50mm.

Fully sealed case suitable for garden layouts, remains dust free  .

Case 1mm thick which supresses radio control.

Shaft suspended on two ball races.

Max voltage direct ( As RC ) 15 volt.

Max voltage live track can be plus 15 volt, depending on leakage.

The Sentinels both use this motor and the two prototypes have  Walsall  30:1 gearboxes and a 9.6V cell pack.

These Sentinels have a top speed of around scale 25mph (more than the prototype which was limited to 17mph!) and will crawl extremely slowly (at a guess a scale 1 to 2 mph).

When I made a mistake with the r/c setting during testing, "Plantagenet" ran off the end of the test track and the torque was such that I had trouble stopping it with one hand (it nearly ran off the end of the table) .... after about 5 seconds the overload cutout stopped it (set to trip at approx.10A) .

Regards,
John.

[classicdelights]

Thanks John.  I will assume a 20% loss for being under load and start from there.

Phil

[cabbage]

You are looking at the WRONG set of gears!!! The "cheap" gears are made from injection moulded Delrin

http://www.muffettgears.co.uk/standard-products/moulded-gears.shtml

If you phone them up I think you will find the prices are a lot cheaper than £34 for 4...

regards

ralph

[classicdelights]

Ralph

These are not the gears Ian designed into the gearbox.  Of the ones specified by Ian, 2 were only available in brass and 2 were Delrin.  I choose all brass as I didn't fancy the combination and the price was more or less the same.

If we are to look at cheaper 'plastic' gears, how are these going to be held securely onto steel axles and shafts?  They will certainly need a mechanical fixing if the gearbox is to last.  If they can be pinned are all members who want the gearbox going to be able to do that or will it have to be done for them?  These are the sort of questions that will need answering.

Phil

[Peaky 556]

Question No.1 is - has anyone tried the 7 pole motor out as yet and if so do you know what its RPM is under load at say 12 volts?  This is fairly crucial to getting the gear ratio about right.

We also really need a straw poll on how many gearboxes are needed.

All the best

Phil

If anyone would like to send me a motor on loan, I will characterise its speed/rpm/current over a range of loads. Picking the "right" load is impossible as everyone will have differing load requirements, eg a small slow moving shutter might never exceed 10W electrical power, but an express pulling ten coaches up an incline might need 70 or 80W, so I will try and bracket the loads so that some interpolation can be done for intermediate loads.

As for quantity, I would require three gearboxes for starters.

Regards,
Tim

[John Candy]

Tim,

I will pack and send this week the six motors you have ordered.

Assuming the design will neatly fit the bogies of LMS 10000, then I would anticipate requiring 4 gearboxes.
If (as I had originally planned in conjunction with Dave) that loco becomes the Flexikit successor to the Sentinel then there is the potential for more sales.....but that is some way down the road.

Regards,
John.

[IanT]

I'm afraid it was me that looked at the wrong 'Muffett' gears Ralph - I downloaded the 'Delrin' spec sheets from their website and worked from those. There were no prices given. However, it should be quite possible to use the moulded gears instead now I have the correct spec. sheets. The design will need re-drafting for 0.5 & 0.7 MOD (etc) but I know it is feasible now - I just need to work out the kinks as they arise.

Just to restate my intentions here.  They were to design a low-cost unit using unmodified commercial components wherever possible. Some assembly & 'other work' will be required and it was my view that if someone was capable of scratch building a loco that required these motor units, then the level of work would probably be within their skills & capabilities - or those of a 'buddy' (if working within a group). I will return to this project eventually, as I have several models that require such units - but it is not currently top of my priorities I'm afraid. I am very far behind in another programme that I (perhaps foolishly) committed to earlier this year and I'm trying very hard to stick to that particular knitting at the moment.

Phil is offering a ready-to-run option that I imagine will be very attractive to anyone who wants a less "DIY" approach than the one I intend to adopt. I hope that enough interest is shown to make his plan viable, as each small development (in terms of Gauge 3 products and solutions) is another step towards wider adoption and acceptance of G3 over time.

Regards,

IanT   

[Peaky 556]

John - I have PM'd you over the motors.
Regards, Tim

[classicdelights]

Just a quick update on this.  Ian is going to look into re-drawing the gearbox to use the cheaper plastic gears suggested by Ralph. When he has done this I will look at what is possible build-wise and make a couple of specimens up.  My initial thoughts are that these gears will have to be pinned onto the axle/shafts as there will not be another secure way to fix them, glue of some sort will not be sufficient.  If the laser cut parts for that version are to be supplied it will be a DIY job in the assembly with some machining required for the axle and other parts.

To have a ready to run version so that members can fit their own wheels and motor will require a substantial commitment from members.  If a better version was to be the ideal we would make the gears to suit the unit but to do that on a commercial basis we would have to be assured that there was a requirement for at least 50 and preferably a 100 units.  We cannot spent the time on the project if there is no demand.  So Gents, if you seriously want a quality RTR unit please email me with your requirements to: flints234@btinternet.com

Neither of the possible options will require no work.  If the Society decides that RTR is the way to go you will still have to fit your own wheels (Loctite) and your own motor into the unit or you could send us your motors for the assembly phase.  If you want the cheap version there will be quite a lot of work required as all the Society will be providing is the laser cut parts and some commercial bits such as gears and bearings.  You will need to machine parts, cut metal, drill holes and be able to silver solder to assemble the unit.

Best Wishes

Phil

[MikeWilliams]

Phil,

"need to silver solder"  what?

Mike

[classicdelights]

Hi Mike

Ian's design has a clamping arrangement that grips the motor and holds it in place.  If you remember, the motor has no fixing points at all so can only be clamped into the gearbox.  The gearbox frames have a hole for the motor to slide into but it will not stay there without some sort of clamping.  The frames have to be slit to form the clamp.  Before the slitting takes place a block that has been bored for the clamping bolt is silver soldered to the frames, one for each side.  The frames are then slit through the block so a bolt can pull the frame opening together to grip the motor.

I hope that explains what is needed.  Ian may revise his design when he redraws it for the cheaper gears but on the face of it there does not seem to be another way to hold the motor in place.

All the best

Phil

[MikeWilliams]

Thanks Phil.

I suspect most of the engineering skills you list we be acceptable to most people, or can be done for them.  I was just the silver soldering which I doubt many would tackle.

Excellent project and I really hope it goes ahead.

Mike

[classicdelights]

Happy New Year to you all

I have been having another look at the gearbox that Ian designed with regard to its use in diesel or electric outline locomotives.  I had previously superimposed the design on a Class 40 type bogie and 2 units would fit comfortably.  I have just had a look at the Bo-Bo situation and as I thought, just one gearbox/motor unit can be fitted to a bogie unless you have bogies that are exceptionally long.  I have tried the gearbox outline on the SR type JA or JB Electro Diesel as I though one of these would be very useful for pulling stock around before it is made available for a steam locomotive, or even for recovering dead steam engines.  I have attached the JPG of the unit superimposed on the bogie to the correct scale for gauge 3.  This loco has 3' 4" wheels so is toward the smaller size range possible with this unit.

As it appears the demand for these units is going to be small it would be unrealistic to offer a RTR option, at least from Dan and me.  If members wish to advance this design as a set of parts to form a semi-kit as Ian has designed it I will get a couple of sets made up including buying the specified gears.  As the gears are going to be expensive I will investigate if they are available in steel instead of brass as that will simplify attaching them to the axle/shafts, steel on steel being more favourable to fixing with shaft-grade Loctite.

Let me know what you collectively think.  My view is that Ian has designed something that will work so we may as well get on and use it.

All the best

Phil

[classicdelights]

Sorry about the picture, this one should be horizontal.  The gearbox frame is outlined in light blue, you can see that it just overlaps the centre of the bogie making the fitting of 2 impossible on a Bo-Bo.  The motor is outlined in a darker blue so hopefully all will be obvious.

Regards

Phil