Axle Hung Motor Gearbox (AHMG)

[IanT]

I did miss the 0.7 MOD 'moulded' gears on the Muffett website Ralph. I downloaded their other 'Delrin' data sheets instead. So I will check to see if we can use the Muffett 'Hostaform' 0.5/0.7 MOD gears, as your quoted prices do seem to be a bit cheaper than HPC's.

However, a quick look at the Muffett 0.7 MOD data sheet (that I've just downloaded) shows their 12t gear to have a 3mm bore and their 40t gear to have a 6mm bore. The motor shaft is 4mm and it would also help to have a common bore for the intermediate gears.

I'll see if we do have a cheaper option and report back - but it may be a while...

Regards,

IanT

[Geoff Nicholls]

would it help to ease the back-to-back out to nearer G3 finescale, say 59mm?

Or should we have a second team working on a motor fixed to the underframe with a cardan shaft and gearboxes on the bogie axles?

[Doddy]

would it help to ease the back-to-back out to nearer G3 finescale, say 59mm?

Or should we have a second team working on a motor fixed to the underframe with a cardan shaft and gearboxes on the bogie axles?

YES! As long as we can have a centrifugal clutch and free wheeling bevel gears! 

[IanT]

I think we may already have a second team Geoff - Gavin's brushless motors look pretty interesting and may be the preferred way to go in this area. But if you want to design a Carden shaft with axle mounted gearboxes (and share it with us) then that would be great too.

The more the merrier!   

Regards,

IanT

[cabbage]

QUOTE:

would it help to ease the back-to-back out to nearer G3 finescale, say 59mm?

UNQUOTE:

NO. Most definitely not!!!! I have never heard of G3 Finescale but increasing the BTB to 59mm would involve redrafting all the curve, crossing and point calculations... Remember it is the portion of the flange that is subtended by the rail that steers it. Thus larger diameter wheels require wider curves and smaller wheels take tighter curves. If you increase the BTB then you remove the amount of arc of the curve intercepted by the leading and trailing parts of the flange.

Going to BR std BTB would mean that you would need BR std curves of 6 or 8 chains... If we examine the Cliff Barker point radius of 4.5m then that is 5 chains(!)

I do remember when I was Secretary getting an e-mail asking why our flanges were unprototypically large, I replied that I would rather be accused of having fat flanges than injuring a child. Remember that you are dealing with a model -the dynamics are different. A model does not have a scale 18 tons per axle sticking it to the rail -800grammes per axle would be very heavy!

regards

ralph

[blagdon]

Well said Ralph, even a diesel outline loco such as Mike H's Class 66 'Shed' is a lot of weight if it were to leave the rails at the wrong place; as for a live steamer.....


Ian the Gauge '3' Pirate

[cabbage]

The e-mail was sent to me on 2009/10/24 -yes I have all the e-mails ever sent me!

regards

ralph

[jamiepage]

'QUOTE:

would it help to ease the back-to-back out to nearer G3 finescale, say 59mm?

UNQUOTE:

NO. Most definitely not!!!! '

I have no particular interest in questioning G3S recommended wheel standards but felt that was rather dismissive of an idea worthy of at least some polite consideration. Especially when presumably these setups will be used for the most part in small wheeled, smallish wheel based locos?
First question could perhaps have been to confirm what exactly are the G3S recommended tolerances on their standards? Plus/ minus what exactly? There has to be a tolerance, and most other standards seem to allow             + something/ -0 on Back to Back.  Just maybe 58.2mm, say,  would have done it.

While I'm at it, I would also question the implied primacy of flange depth in protecting children from injury, in an aside which didn't seem to be related to the topic.
Whilst a matched set of wheel and track standards is clearly important, the statement (and the response)  could be interpreted as giving too much 'credit' to flanges alone. Having flanges exactly on spec. is not going to prevent derailments in the garden railway environment.
Driving skill, driver error, speed, signalling error/ collision, general state of track, wheel wobble, loco chassis alignment, spring/ weight distribution, have all surely contributed more to the derailments which have occurred. Perhaps, if injury is really considered that likely, then some thought should be given to where an audience may observe operations.
To state that deep flanges are preventing derailments without context could unwittingly play down other likely contributors to derailments. Are wheel standards checked at G3S GTGs?

Again, I have no real complaint with G3S recommended 2.0 mm (sprung), 2.3 mm (unsprung), but if it's that critical then what are the tolerances? How much springing is needed before the 2.0mm option becomes acceptable?
How much safer would Greenly's 3.175mm be?

I apologise for sidetracking this interesting thread.  John, please move or remove if it gets in the way.

[cabbage]

Jamie,

Your points are well thought out and I would like to answer them.

I use the wheel and track standards that date prior to the 2010 revision. There has never been a +/- tolerance on any of the measurements... The flange steers the loco by the continuous sliding motion against the rail. In the G3S std this is 10 degrees thus the centring force per axle is tan(10) multiplied by the weight per axle -per axle. You are quite right that the flanges alone will not prevent the loco from de-railing. Primary de-railing factor is the "flanges climbing the rail". This can be minimised by the following standard techniques. Transitional leading straights into the curve, gauge widening on the inside of the curve -thus forcing the flanges of the wheel into contact with the outside rail of the curve and thus also forcing the coning of inner wheel to the smallest diameter. Super elevation of the curves also helps, I have found the formula as promoted by HG to be too high and the one used by PennRR to more suited to tighter curves. A valid alternative and it is one that I use is to have the axles on wagons free independent running i.e. the axle is fixed and the wheels spin on bearings.

My track is designed for high speed running. Thus I have opted for a very simple trick to safeguard small visitors all curves face outwards from the viewing point and any high speed derailments have a trajectory into a bush!

I do not check my visitors BTB but trust them to have set them to the required standard as listed. Nor do I check the wheel thickness as my wheels are all 8mm thick. All of my flanges are cut to 2.3mm regardless of wether or not they are sprung and the bases of the frogs are set that a 2.3mm flange will run along them and intersect the point of the frog on the cone with no vertical component to the motion.

Double flanged wheels are not uncommon in narrow gauge wagons and snow ploughs to prevent de-railments.

Having checked "Model Railways" (I have the 1924 ed) p47 the BTB given is 58mm with a flange of 3.2mm (1/8th inch). Would I use it? Most definitely!!!

However the modern model is far lighter than those designed by HG and as such I would say that springing is becoming more problematical -his method was to use a pair of snips and work your way around the spring until it worked. Personally speaking I would say that compensation rather than springing should be adopted to ensure perfect wheel to rail adhesion. So the question of how much springing do you need really depends on how poor the track work is... If you can say that the flange never goes above the top of the rail then that is all you need to have. HGs fat flange is due more to the poor track work that was made then. Modern plastic sleepers and extruded rail are far more accurate than that supplied by "Bonds o' Euston" for example.

regards

ralph

[jamiepage]

Ralph,
Thank you for your courteous reply. I don't want to overstay the time in this particular thread, because it is an interesting discussion and could do without digressions. Suffice to say, I have no real problem with the G3S recommended standards as such ( any standard is a compromise; one can't really start with a clean sheet of paper and at he same time recognise legacy standards; it works; one standard and one scale is a good thing) but there are a couple of areas within it I would like to explore, as touched upon here. (Specifically, tolerances within a standard, and flange dimensions).  I will, sometime over the next few days, continue this in a new thread.
Yours
Jamie

[cabbage]

Jamie,

I presume this is what you are referring too?

http://ts.spur-ii.de/IGSpII/Standards_IG-SpurII/IGS2-S02--2002-03--Radsatz-Radreifenprofil.pdf

Sorry I spent a few minutes studying it before I realised what was "wrong" -it is in German....

http://www.g1mra.com/pdf/standard-dimensions-for-gauge1.pdf

As you can see the Spur II wheel is a derivative of G1MRA -whilst G3S is more from "real world" and both pushes and pulls the axle.

http://www.gauge3.org.uk/technical.html

I await your new thread with interest!

regards

ralph

[IanT]

Gavin & anyone else wanting another potential solution to G3 axle hung power....

There is a very interesting article by Jon Freeman in the latest EIM about Brushless DC Motors (and their control electronics). He's using them for a 5" loco and he believes that DC 'brushed' motors are probably now effectively obsolete in many applications ...

HQ7P Update - I've not spent too much time on the HQ7P A/H gearbox recently, partly because I offered to do something else ( "a quick job" ) and it's taken a bit longer than I originally assumed - but that's almost finished now.

I did manage a HQ7P CAD design that was probably "buildable" (at least I believe I could most likely build it) but unfortunately it's too complicated and probably not cheap enough to be practical. I'll have another look at it once I've finished the current work. However, I've possibly already spent too much time trying to find a solution to using the HQ7P in this particular application. Perhaps it's time to start looking at other alternatives that can meet the criteria (e.g. ease of assembly, uses commercially available components and has a low overall cost per gearbox and/or motor).

Regards,

IanT

[classicdelights]

Hi Ian

Unfortunately, many of us have bought the things now.  Hoping for a solution.

Phil

[cabbage]

Well I have an advanced education in "cheapness" due to my upbringing. Send me a CAD file and I will see what  the build budget can be shrunk too!

regards

ralph

[Doddy]

EIM ?