Roxey Gearboxes

[Steph Dale]

Rob, are the bearings a direct fit, or do you need to make modifications ?

Phill,

I'm just gonna butt right in here...:

No mods needed in my experience, just open the holes in the frame up to take the bearing and then assemble as per normal. Of course, the ball races need to fitted with epoxy after all the other soldering is done.

So, rough order for assembly with ball races (should have done this before! ), the method would need a slight change around steps 3 to 6 if using plain bearings, soldered in:
1 Burnish the gears to remove any burrs or roughness
2 Open out the holes in the fret to take the bearings, motor screws, motor bearing boss etc.
3 Fold up and assemble frame - as square as possible, with solder reinforcement to each fold and joint.
4 Clean up frame and blacken or paint if desired.
5 Using a 'jury' axle fit the ball races to the frame with epoxy.
6 Allow epoxy to cure.
7 Fit the motor with screws just nipped up.
8 Fit worm to motor shaft with a 2mm id washer between motor bearing boss and worm gear to take out any slack - but don't make it tight enough that it impedes the motor turning (I use Alan Gibson turned brass ones).
9 Fit gear to jury axle, centred under worm.
10 Adjust mesh, tighten screws.
11 Test run motor and gearbox.
12 Once happy it's smooth and quiet lock off the motor fixing screws.
13 Run in with a good quality gear lube.

Running in should be done gently at this stage (say 15mins one direction, rest for 15 mins, 15 mins other direction, rest for 15 mins, repeat) so that the motor doesn't overheat and so that the initial wear on the gears is even. Once the motor/gearbox has accumulated a total of about an hour in each direction it can then be considered ready for installation into the model. I assume we all run in motor/gearbox units on the bench before installation - whatever their source? Whaddya mean, no? Seriously, it's good practice to get the motor brushes bedded in properly, ensure the motor bearings don't get deformed, burnish the gears, etc, etc. But mainly to ensure that if you get any poor running once the motor is fitted to the chassis - you know it's not the motor/gearbox unit that's the problem.

Steph

 

[Steph Dale]

Hi Everyone,

If you are looking for a supply of ball races here is a link to a good firm. The same size as Steph uses in both mild and stainless steel.

http://simplybearings.co.uk/shop/p155026/FR156ZZ Metal Shielded Flanged Deep Groove Ball Bearing 3/16x5/16x1/8 inch/product_info.html

http://simplybearings.co.uk/shop/p155080/SFR156ZZ Metal Shielded Stainless Flanged Deep Groove Ball Bearing 3/16x5/16x1/8 inch/product_info.html

Susie

Susie,

Thanks for the link , I can see some useful goodies there.
You might find that Arc Euro Trade or RC Bearings are better value for money for the sorts of sizes we need (typically FR156 and FR166 families of 3/16" inside diameter bearings).

Steph

 

[Simon Dunkley]

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.

80kph is near enough to 50 mph, and 1100mm to 3'8"...

OK, so you fit a high ratio for ultra-slow running on your plank. Do you realise that you are going to be running the motor flat-out a lot of the time? Not a good idea - and what happens when you pay a visit to a friend with a roundy-roundy?

Given a decent motor and good quality gears, then a high ratio is not required. In fact, I have seen really, really good running using a DS-10 and one of the old Alan Gibson plastic gearboxes. The best running loco I had as a kid had an X04 plus the silly ratio that Triang-Hornby fitted - about 23:1, I think, because to the two-start worm. Could put on a fair old lick, put on a simple resistance mat, could come down to a crawl - and it didn't make any noise, either!

 

[Phill Dyson]

At present all my 7mm kit built diesels with one exception are running 13:1 gear sets which are perfectly capable of ultra slow running, but with lots of power in reserve when you need it.

The one exception to this is my Class 33 which has a much higher ratio S/H motor bogie , this gives the loco a top scale speed of about 20mph to 30mph.....with no power in reserve this loco is incapable of pulling anything beyond half a dozen wagons & will be fitted with a 13:1 gearbox at the earliest opportunity.

 

[mickoo]

80kph is near enough to 50 mph, and 1100mm to 3'8"...

OK, so you fit a high ratio for ultra-slow running on your plank. Do you realise that you are going to be running the motor flat-out a lot of the time? Not a good idea - and what happens when you pay a visit to a friend with a roundy-roundy?

Given a decent motor and good quality gears, then a high ratio is not required. In fact, I have seen really, really good running using a DS-10 and one of the old Alan Gibson plastic gearboxes. The best running loco I had as a kid had an X04 plus the silly ratio that Triang-Hornby fitted - about 23:1, I think, because to the two-start worm. Could put on a fair old lick, put on a simple resistance mat, could come down to a crawl - and it didn't make any noise, either!

Simon, thanks for the explanation and conformation that lower ratios still offer good slow speed operation.

Kindest

 

[Simon Dunkley]

No problems, Mick.

There is an easier way to do all this*, which is to divide the motor rpm by the following, depending on loco type, to get a gear ratio:

Older (Victorian) steam loco: 400
Modern steam loco: 700
Diesel: 1,100
Diesel mechanical: 350
08: 120
09: 200

*Which only makes sense after going through the other stuff!

These are all rough approximations, but they help get you into the right part of the ballpark. As you can see, though, higher speeds with smaller wheels means more revs per minute (if they form a line, do they get a queue-rate?) which was only possible with improvements in materials and bearing technologies, hence bigger wheels in the 19th century.

 

[Simon Dunkley]

PS - lower gear ratios are usually more efficient, so err on the side of low rather than high.

 

[mickoo]

I presume modern electric locos would still fall into the diesel 1,100 range with their slightly larger 4'+ wheels.

I've no idea where you got those magic numbers from, most impressive LOL and certainly help in deciding which gearbox to go for, 13:1 seems to fit the bill from the Roxey range for my intended projects, the 26:1 would be more suited for the Krauss Maffi MH05C or Jung ED80T, both low speed shunters.

Kindest

 

[Simon Dunkley]

I presume modern electric locos would still fall into the diesel 1,100 range with their slightly larger 4'+ wheels.

Yep.

I've no idea where you got those magic numbers from,

Well, if you wish....
(It's as simple as pi, really.)

13:1 seems to fit the bill from the Roxey range for my intended projects, the 26:1 would be more suited for the Krauss Maffi MH05C or Jung ED80T, both low speed shunters.

Got it in one!

 

[mickoo]

(It's as simple as pi, really.)

It's been a long day on the end of a crane boom 100' high over the river in 40+ winds so I'm a bit brain dead (at least it didn't rain and was mild), so I'll take your esteemed word it's simple LOL.

Thanks again.

 

[Dog Star]

It's been a long day on the end of a crane boom 100' high over the river....

That seems to be a bit tough... what is wrong with the D-cap and the stool in the corner?

 

[mickoo]

That seems to be a bit tough... what is wroing with the D-cap and the stool in the corner?

LOL, tough, that's not tough, the real short straw is the top of the crane 230' high. I was surprised at how much pummelling the body gets at just 40mph, its a nice view and I got some nice photos at lunch time http://www.flickr.com/photos/32755955@N05/7467816234/in/photostream but it really does sap your energy.

Anyway, back on track, just ordered some Roxey gearboxes, and some bearings, now looking for provider of Canon 1833 motors.

Addendum, just found a good shot that shows where I was working the other day, on the end of the boom at far left installing load transducers for part of a system I helped develop to protect the crane from overloading. http://www.flickr.com/photos/32755955@N05/6972915186/in/photostream Sorry for the OT.

Kindest

 

[daifly]

to see what they do to keep the stacks stacked on ships!!! There must be some kind of lock - and presumable some poor sap who has to put them in place....

Perhaps not!

 

[Dog Star]

Not a lot one can say in response to that.... I shall leave the floor clear for Jordan!

 

[Phill Dyson]

Can we stick to Roxey Gearboxes please guys

Thanks Phill

 

[mickoo]

it could depend if it is being subject to thrust loading or not

Two 13:1 gearboxes turned up today , there is no input shaft bearing, the worm goes direct onto the motor shaft and that bearing is the input bearing as such, also had delivery of FR156zz bearings from RC Bearings, quite quaint little affairs really. OD is 7.94mm and etched hole is 6.1mm so they do need to be bored out a little, not sure of the best method to do this, suspect a drill will grab the thin etch, tried a hand tapered reamer and after 5mins only opened out an extra 0.3mm , I'd of expected more from a brand new reamer.

Kindest

 

[Rob Pulham]

Hi Mick,

I use a tapered reamer but it seem to do better than yours.....

 

[mickoo]

Well I decided to get manly with it and it worked, will assemble tomorrow and see how it all fits together, it looks like it might even fit inside the SD45 motor brick as a replacement for the Aristo half axle gearbox assembly.

Kindest

 

[Steph Dale]

D

Hi Mick,

I use a tapered reamer but it seem to do better than yours.....

Ditto - I've also got a 15" bastard cut round file, which works well....

Steph

 

[mickoo]

D

Ditto - I've also got a 15" bastard cut round file, which works well....

Steph

Yes a file was used up to 7.5mm then the reamer for the rest of the way.

Kindest