What Gears, What Muffs?

[Argos]

I've just spent an afternoon getting confused (not hard! ) trying to work out which gears and muffs to use from shop 3.

 

I am now the proud owner of a Worsley Works Macintosh 439 0-4-4t etch to build for my boxfile layout, but I am finding the whole concept of the chassis build a bit daunting.

 

All my builds to date (7mm scale) have used a combined motor and gear box that even I would struggle to louse up.

 

The boiler on these engines is quite small, so, I have a Nigel Lawson (http://www.nigellawton009.com/6VMicroMotors.html) micro motor on order along with the required sleeving to enable a society worm gear to be mounted.

 

My initial thoughts would be to have the gears driving a dummy axle with around a 30:1 ratio then use a pulley system (also on order from Mr Lawton) to give a further reduction (around 1:3 using a 1.7mm and 5mm pulley) onto the drive wheels.

 

The reduction might seems quite large at first, but the prototype has 5' 9" drivers and the micro motor revs upto 30,000 RPM, combine these with a short layout and the choice for a high reduction is obvious. I am also using DCC so could limit the motor that way.

 

which gears and muffs should be used, there seems to be a myriad of choice?

How do the worms relate to the gears and what is the difference between the 100DP 30:1 gear set and the M 0.25 30:1 gear set?

[2mm Andy]

Argos,

 

That's a lot of questions. I'll try and answer a few (there are others on here far better qualified than I am to answer questions about chassis design).

 

To all intents and purposes the 100DP 30:1 gearset and the M0.25 are equivalent - the M0.25 is a replacement as it's getting difficult to source the DP gearsets. You will find data (sizes, meshing centres, muff types) for all the gears in the yearbook which will be coming out with the next 2mm magazine.

 

I would also recommend the booklet on split frame chassis construction which is available from Shop 1 - well worth £5 of anyone's money! If you've got the earlier 2mm magazines from this year, look-up the article in the Feb/March 2012 magazine about the M7 0-4-4t loco - there are some very good ideas in that.

 

Andy

[richbrummitt]

DP stands for diametric pitch and refers to thee number of teeth on a fixed diameter wheel. The size of the tooth diminishes for larger numbers. These are slowly dying out of the association range. Metric gears are measured in module. The smaller the module number the smaller the teeth. (There are many reasons why metric gears are preferable from a production perspective.) Keep the two types separate to avoid headaches. The range of muffs has exploded to suit particular centre bores for the various gear ranges the association has stocked and still supports (while stocks are still available in some cases). Muffs can therefore be a minefield. The shop listings do make sense if you know what gears you wish to use (and here is where the yearbook and book Andy recommends along with various articles in the magazine can help) because the descriptions for the majority of muffs state where they are for specific gears or ranges of gears. The gear muffs are made concentric and have a flange on them to aid fitting two gears next to each other. 3-100 is for non-geared axles. The concentricity of these has improved and you may find that you can run a gear on them happily enough (although only the imperial (DP) gears will fit). For the pony wheels the smaller 3-103 muffs reduce the visibility of the muff around the truck.

 

What you suggest sounds okay. I would suggest placing the pulley before the worm and worm gear pair if possible.

[Tony Simms]

Check the Association website. There is an note on the phasing out of DP gears and the introduction of metric. I believe (without checking most recent return from Shop 3) that the 100DP 30:1 worm and gearsets are now sold out. Order and use the metric item; it has identical centres to it's predecessor. There are still a fair few 21:1 100DP units, so these won't be replaced for a while.

 

Muff descriptions were updated a couple of months ago to give exact descriptions of outer diameter and, where appropriate, their intended gear use. Do not use the axle muffs 3-100 for gears. Whilst it might run okay, why jeopardise all your hard work and many hours for the sake of a few pence? There are a couple of stepped gear muffs for esoteric uses, but 3-102b will become the de facto gear muff as DP gears disappear; this will take one or two metric gears.

 

Presumably the pulleys are 1.5mm bore so won't fit any muff and therefore can't drive a wheel direct. I'd do as Rich suggests and use the pulley reduction first.

[Argos]

Thanks for the informative response gentlemen.

 

I found the notes on muffs in the Apr/May magazine late last night which helps a lot.

I also realised after posting above last night that the 1/8" bore gears equate to the 3.2mm muff (in the words of the immortal philosopher Homer Simpson DOH!)

 

I think I know what I need, I guess it's a case of order the parts and see what combination fits.

The trials and tribulations will appear on the blog in due course.

 

Argos

[2mmMark]

If you were to use a pulley reduction as the final stage down to the wheels, consider how would you replace the drive belt if required. You'd need a demountable wheelset. Not impossible but an added complication.

 

Mark

[Argos]

Good point Mark, I hadn't thought of that.

 

I might need a re-think!

 

Thanks for the advice.

 

Argos

[Donw]

If you are designing gear trains for yourself (rather than using the etched chassis where it has been done for you). Do consider the association gear meshing tool which enable you to mark of the centres for any gear combination (3-271).

Don

[Crosland]

The 3-102b that I was supplied with do not have the rim for pressing the gear against. Is this correct?

 

Andrew

[Nigelcliffe]

The 3-102b that I was supplied with do not have the rim for pressing the gear against. Is this correct?

 

Andrew

Doesn't sound correct to me - check with the shop keeper.

[2mm Andy]

The 3-102b that I was supplied with do not have the rim for pressing the gear against. Is this correct?

 

Andrew

I've just found a packet of 6 gearmuffs marked 3-102b and none of them have any flanges.

 

As Nigel says, worth checking with the shopkeeper.

 

Andy

[Nig H]

The 3-102b that I was supplied with do not have the rim for pressing the gear against. Is this correct?

 

Andrew

Hello Andrew,

 

I think this is correct. There is a description of the new range in the April/May 2012 Mag, page viii.

 

Nig H

[Crosland]

Hello Andrew,

 

I think this is correct. There is a description of the new range in the April/May 2012 Mag, page viii.

 

Nig H

 

Thanks. It would be good if the shop website description were clear on this being a plain muff.

 

Andrew

[Valentin]

Maybe this can help:

 

 

The Association part numbers in the picture:

• 3-110: Locomotive axle steel 1.5mm dia x 75mm long
• 3-102b: Acetel gear muff 3.0mm o/d (metric gears)
• 3-364: Gear-set M0.25 30:1. Skew cut brass gear 3.0mm bore. Acetal worms 1.5mm and 1.0mm bore
• 3-385: Spur Gear Brass M0.4 14T 3.0mm bore
• 3-387: Spur Gear Brass M0.4 18T 3.0mm bore

The next step, after enlarging the muff's bore in order to accommodate the steel rod is to push the gears onto the muffs. This being a very tight fit, can the more experienced ones explain how to do it without damaging the muff? I don't think reaming with a broach would be a smart idea as this is askew...

Edited June 22, 2014 by Valentin

[richbrummitt]

I put the gears on before inserting the stub axles and use my pillar drill as a makeshift press once the muff is started into the gear. A tiny chamfer on the muff can get you started if things aren't working out.

[Izzy]

With parts like this where shafts are inserted into bores it is always helpful if the edges of the bores and ends of the shafts are 'broken' i.e. de-burred or very slightly chamfered, to allow the shaft to enter the bore without tearing either itself or the bore. Often with machined or moulded/extruded parts some edges can be rough/uneven. For the gears I use a scalpel blade to do this - poke the blade into the bore and slide the sharp edge around the bore edge - and for the muffs just a flat needle file to chamfer them.

 

I always mount the gears on the muffs before any attempt to fit a shaft into the muffs. This is normal when fitting gears on idler muffs, but I can't imagine doing it any other way. I usually use a small smooth face vice to press a gear onto a muff. But placing the gear on a flat surface and tapping the muff in (gently) with a small plain face hammer also works well. Placed between two raised blocks this is the way I adjust the position of a gear on a muff.

 

I never put a drill or anything else into a muffs bore before inserting a shaft. There should be no need to enlarge the bore.  Generally I find the 2mm association axle steel and wheel stub axles make a firm but not overtight fit into the muffs. I have often found the need to drill a cross hole through the centre of a muff and use a drop of loctite cryno or 601 to stop the axles turning in the muff.

 

Izzy

[Valentin]

It seems there is no data in the 2019 Yearbook for the following metric gearsets in the Shop (I could find only for the imperial ones):

• 3-363 - Gearset: M0.25: 21:1 Skew Brass Gear 3.0mm Bore: Acetal worms 1.5mm and 1.0mm Bore
• 3-364 - Gearset: M0.25: 30:1 Skew Brass Gear 3.0mm Bore: Acetal worms 1.5mm and 1.0mm Bore (currently out of stock)

I am confused about the below:

• the Shop has the 3-363 for the 21:1 metric gearset but the Yearbook shows this code for the 38:1 imperial gearset.
• what is the difference between the new 3-367 30:1 100DP gearset and the old one, withe the code 3-362, also 30:1 100DP.

Any feedback, really appreciated.

[2mm Andy]

4 minutes ago, Valentin said:

It seems there is no data in the 2019 Yearbook for the following metric gearsets in the Shop (I could find only for the imperial ones):

• 3-363 - Gearset: M0.25: 21:1 Skew Brass Gear 3.0mm Bore: Acetal worms 1.5mm and 1.0mm Bore
• 3-364 - Gearset: M0.25: 30:1 Skew Brass Gear 3.0mm Bore: Acetal worms 1.5mm and 1.0mm Bore (currently out of stock)

I am confused about the below:

• the Shop has the 3-363 for the 21:1 metric gearset but the Yearbook shows this code for the 38:1 imperial gearset.
• what is the difference between the new 3-367 30:1 100DP gearset and the old one, withe the code 3-362, also 30:1 100DP.

Any feedback, really appreciated.

 

Valentin,

 

The meshing centres for the metric gearsets were designed to match the imperial ones that preceded them.

 

There has been some renumbering of products over the years, so it seems that the number for the old 38:1 100DP gearset has been re-used. I'll ask the Yearbook Editor to review and amend the next yearbook.

 

The only difference between the new 3-367 and the old 3-362 should be that the old ones were made by Ultrascale (and later by Bill Blackburn) and the newer ones are made by Alan Smith. The new batch were produced due to problems with the supplier of the metric gears. 

 

Andy

[Valentin]

Thanks, Andy. Pretty clear now. I should've used the forum's search function before posting the question. I must be getting old now as I asked nearly the same question three years ago!