Roxey Gearboxes

Steph Dale

Steph Dale

Western Thunderer
Guys,

Erm, another response to a query so, why Roxey gearboxes?

Well they run smoothly thanks to decent (Markits) gears and have an intelligent design of fold-up gearbox which supports the gears in all the right places, in all the right ways.

Bob Alderman did a nice piece on assembling them in the Gauge 0 Guild Gazette (Vol 17, No 7) a little while ago, and reading that will do much to get you going. On re-reading it I can see that Bob uses the same tweak I do, in setting up the bearings pointing inwards.

Here's a pic of the gearbox assembled, again for my recent demo Jinty chassis (which should also appear in the Gazette in due course), which is why the motor is represented by an appropriately-sized piece of brass:
IMG_1327.jpg

To get the two bearings and the gear in there required one of the bearings to be slightly trimmed for length, but I don't always find this to be necessary. It's done on the end of a 3/16" diameter stub-axle in this case - a short length of silver steel would work fine too:
IMG_1323.jpg
IMG_1324.jpg

So that's that eh?

Well no. The main trick is to put the bearings in the frame after the frame is assembled. It's worth opening the bearings holes up while the parts are flat though. The bearings can be soldered in using a 'witness' or 'jury' axle or length of 3/16" silver steel. They're then aligned for good.

The resulting running can be superb, I've got one of these in the 2251 which was used to show how I put my inside motion together and the running with a Canon 1833 is superb. Smooth, powerful and silent. The Canon 1833 offers about twice the power than the Mashima equivalent, seems to be better made generally and has a higher top speed - it works a charm with the 40:1 Roxey 'box.

There is an alterior motive to me using these - there is just enough clearance in the offset gearbox arrangement to allow a split axle:
IMG_1388.jpg

But you do need a very narrow split; see the top axle here:
IMG_1397.jpg

One last trick? Okay - use ball races rather than plain bearings for the final stage. A couple of small spots of epoxy to hold them in place and you end up with a pretty impressive unit...

Steph
 
Phill Dyson

Phill Dyson

Western Thunderer
Thanks for posting this Steph :):thumbs:........very useful as you know I will be doing some of these soon ;)

Cheers Phill
 
westernfan

westernfan

Western Thunderer
Was looking at the mashima /markits motor ,gearboxs as i need to replace the setup in my o gauge pannier is the canon roxey combination that much more expensive ?
Any ideas how many milli amps current the canon draws ?
 
Steph Dale

Steph Dale

Western Thunderer
The Roxey 'box, I suspect, is a couple of quid more than the Markits one, but the frame is soooooo much better...

The Canon is getting on towards £25, but then so's the Mashima. In terms of current (you're thinking about DCC decoders I guess?) it does, of course, depend on the application. The Canon is a 4w(ish) motor so the current draw is about double that of the 2w Mashima, but well within the capabilities of the average HO/00 scale decoder - under normal conditions it'll be around 0.5A max.

Steph
 
mickoo

mickoo

Western Thunderer
Perfect timing, looking to use these for some Gauge 1 projects with 3/16th axles, glad you mentioned roller bearings, that's one question off the list :), my intention is to use both ends of the Mashima with a gearbox on each end (haven't fully mentally worked out if thats possible with the same worms and gears yet LOL, its been a long day) as a power bogie sort of assembly, not sure if Canon motors are dual ended?.

Final thing is to work out which ration 26:1 or 40:1 more suits a diesel in 1:32 scale, I think ABC/ Ron Chapman did a speed/ratio chart somewhere, not sure if it catered for scale as well, that's this evening next project after uploading todays photos.

Thanks for sharing the info, greatly appreciated.

Kindest
 
Steph Dale

Steph Dale

Western Thunderer
Mick,

Couple of points to pick up on there:

You don't need speed to relate to scale - it's a function of axle rotation speed (rpm). The difference in scale is handled by the wheel being a different size for a different scale. There is a low-res speed/gear table on the ABC website.

Canon (and Mashima) motors are both double ended. There seem to be a number of variants of Canon out there; the versions for sale on eBay don't even match the Mashima specs and tend to be single ended. The Roxey one is the same as that used by ABC and has roughly 10mm shafts. The Branchlines ones have a slightly different spec on paper, but retain the same good power/speed performance; they have 15mm shafts. In all cases I should add that I'm describing the last versions I've had from each source. Neither the Canon, nor Mashima 1833 have rear motor fixings worth a dime.

I hope that helps a little.

Steph
 
mickoo

mickoo

Western Thunderer
Steph,

Ahhhh, good point, forgot about the larger wheels adding the extra speed and thanks for the added info on rear motor mounts, must be a way to do it though, even if via another sub frame linked to the first, might be an issue if you wish to individually spring each axle mind?.

Off to ABC now, images from todays shoot uploaded so it's now some toy train time LOL.

Kindest
 
Rob Pulham

Rob Pulham

Western Thunderer
Steph Dale said:
Well no. The main trick is to put the bearings in the frame after the frame is assembled. It's worth opening the bearings holes up while the parts are flat though. The bearings can be soldered in using a 'witness' or 'jury' axle or length of 3/16" silver steel. They're then aligned for good.
Click to expand...

Hi Steph, thanks for this tip I used a Roxey gearbox in Severn and have a few in the drawer lined up for other builds. I like this particular tip as I have soldered the bearings in on the flat before. I will try the roller bearings tip too.:thumbs:
 
Steph Dale

Steph Dale

Western Thunderer
Guys,

Thanks for the comments, but can we nail a personal 'tick' please? :confused: A roller bearing and a ball race are not the same thing. Ball races, particularly the smaller flanged type (I tend to use stainless steel versions - SFR156zz if I can get 'em) are great for this appliocation. Roller bearings? Well, you're on your own then...

Steph
 
mickoo

mickoo

Western Thunderer
Ok, I am suitably admonished :oops: LOL, I should know better being in the engineering trade :).

Kindest
 
mickoo

mickoo

Western Thunderer
Is it possible to put a roller bearing, ahem, ball race in the worm 2mm input shaft?.

Also, I always see Mashimas and Canons mounted with flat sides outward, is it possible on the gearbox to mount them flat sides up and down?, I have no issue with width restrictions but some with height under bogie pivots etc on DE locos, DH is no issue with their UJs and drive shafts.

Kindest
 
S

Simon Dunkley

Guest
Rough calculations which may be of use:

Driving wheel RPM = 28 * speed in mph/wheel diameter in feet.

For Victorian steam locos, where the materials science hadn't advanced to the point of allowing high piston speeds, they generally used the driving wheels to get the speed they wanted, and you can go for 5' diameter = 50 mph, 8' = 80 mph, etc, i.e. an rpm of 280, call it 300 rpm. For later designs, you might want to increase it to say 500 rpm. (Mallard was probably running at about 525 rpm when it achieved 126 mph.) For diesels, 800 rpm is about right - unless you are modelling HSTs (say, 1,000 rpm)! For diesel shunters, it may be as low as 90 rpm for an 08, 150 rpm for an 09, and 250 rpm for one of the "mechanicals"

In theory, to get the gear ratio you divide the motor maximum speed by the driving wheel rpm, and leave it at that. However, the maximum speed is without load, and a friend who is a very respected modeller and used to earn his crust design medical instruments, suggested to me that you take 75% of the no-load speed when deciding on the gear ratio.

More sums, then - these are all approximate, so you simply get the nearest which fits:

So, for a 10,000 rpm motor, you can proceed as follows:
75% of the no-load speed is 7,500 rpm.
For a Victorian loco, or something like a shunter, the gear ratio would be 7,500/300 = 25:1;
For a 20th Century loco, the gear ratio is 7,500/500 = 15:1;
For a diesel loco, the ratio would be about 9.4:1 (10:1 or 9:1 would do - these are all approximate!);
For shunters, we get 30:1 for the Gardner 204hp family, 80:1 for an 08, and 50:1 for an 09.

So, depending on loco, we get a range from 9:1 to 80:1 for the same motor!

An alterntive to the high ratios, if you are using DCC, is to limit the maximum voltage, and have a lower ratio gearbox! (If using two motors, you could wire them in series... ...but let's not complicate things!)

Incidentally, the larger the motor, then generally the lower the revs - this also applies, to some extent, to the ratio of length to diameter, but these are simplifications applicable within similar design types, e.g. Mashimas.

Hope that helps - the practical upside is that if you can find a good motor which suits most or all of your purposes, you can adjust the maximum speed by choosing from a limited range of gear ratios.

Must admit that I always thought that the much vaunted RG4 gearboxes, coupled to the meaty and powerful 1624 motor, were a bit slow on the driving wheel RPM. The 1616 was faster but had no guts in comparison!

Simon
 
JimG

JimG

Western Thunderer
Simon Dunkley said:
Must admit that I always thought that the much vaunted RG4 gearboxes, coupled to the meaty and powerful 1624 motor, were a bit slow on the driving wheel RPM. The 1616 was faster but had no guts in comparison!
Click to expand...

Simon,

I would agree - having just dug my RG4 S scale locos out of their long term storage and given them a service, I had forgotten how slow the top speed was. At first I thought there was something binding in the chassis, but checking an RG4 on no load confirmed the slow speed.:)

Jim.
 
mickoo

mickoo

Western Thunderer
Simon, Oh dear, math LOL, I kinda get all that, sort of, not sure how to apply all that to a 1100mm wheel at 80kmh mind, but I'm sure I can work it out :). The only issue I can see with all that is the higher the top speed the higher the ratio and the less slow speed fidelity. So one could argue that if your building a shunting plank or slow speed layout, like a depot or station etc you could forsake top speed with a lower ratio and gain better slow speed control?, your stock is rarely going to be getting anywhere near its top speed.

Kindest
 
You must log in or register to reply here.
What's New?
Top