Drive components for electric locos and EMUs

User avatar
Guy Rixon
Posts: 701
Joined: Sun Mar 27, 2011 6:40 pm

Drive components for electric locos and EMUs

Postby Guy Rixon » Sun Jul 15, 2018 10:38 am

I need to build a number of electric locos and EMUs: ultimately, two pairs of MDR locos, one Metropolitan loco with centre cab and one with two cabs, one MDR EMU, one Metropolitan EMU (possibly two if I do one for the H&CR) and one LNWR EMU. It's actually unlikely that I'll live long enough to build them all, but I hope to do at least a few, starting with the MDR locos.

I'm considering a single-ended drive in each loco, giving two driven bogies in each pair and two dummy. I home to use N20 gear-motors with bevel gears for the final drive. The motors would be in the bodies of the locos and linked to the driven bogies with Cardan shafts.

I think that I can build the driven bogies with rigid primary suspension since the wheelbase is only 7'. This makes it vastly easier to build the drives. The trailing bogies would have moving suspension, probably one rocking axle for simplicity, in order to get better pick-up. I'll probably try a sprung, secondary suspension to stop the bodies lurching too much.

I've ordered some N20s and a bag of el-cheapo bevel gears. Still need to buy prop-shaft components, but I'm tempted to try the 2FS approach of a spring-steel prop-shaft with a loop at each end running in slotted collars. I don't expect these locos to pull heavy trains, so I think this approach might hold up; and it's cheap, like me.

I'm hoping that this kind of drive can be extended to all the EMUs too. The only electric trains I'll build where I definitely can't use it are the Metropolitan locos, as these ran singly and need a drive to both bogies.

One other thought: would it be worth actually electrifying the conductor rails and picking up from those?

Crepello
Posts: 104
Joined: Thu Jan 31, 2013 11:32 am

Re: Drive components for electric locos and EMUs

Postby Crepello » Sun Jul 15, 2018 12:13 pm

As your final drive via the bevel gears is 1:1, the torque on the cardan shaft is going to approximate to the traction torque on the driven wheelset. This is then going to react with any suspension, including bolster slack, between the vehicle body and the bogie. This may not be a major problem with your intended lightly loaded trains, but it could trip up anyone following in your footsteps.

It's such an expensive job, arranging D&E transmissions, other than cannibalising spares from the RTR industry-standard setup!

User avatar
Guy Rixon
Posts: 701
Joined: Sun Mar 27, 2011 6:40 pm

Re: Drive components for electric locos and EMUs

Postby Guy Rixon » Sun Jul 15, 2018 6:39 pm

OK, I'll watch out for the torque-reaction problem; thanks for the warning. One of the attractions of designing with such cheap parts is that I've lost little if it doesn't work as expected.

If I was designing with complete freedom, not needing to use particular. commercial parts, how would I get round the reaction problem? Presumably, I'd need to build further reduction - spur gears - into the bogie so that the torque on the prop shaft could be less for a given acceleration. This might be a good thing even in the low-torque regime, in that the prop shaft could be horizontal and still line up with the motor axis.

seanmcs
Posts: 33
Joined: Wed Dec 10, 2008 12:57 am

Re: Drive components for electric locos and EMUs

Postby seanmcs » Sun Jul 15, 2018 11:05 pm

Have a look at the Steam Era Models web site. Based in Melbourne, they sell a Black Beetle powered bogie with the motor and gears in the bogie. I just got one in P4 for conversion of the Dapol GWR diesel railcar. It is not a very powerful motor but might be suitable. I note your first idea uses inexpensive products, so at somewhat over AUD 100 including postage, the BB may be too pricy.

Sean

Alan Turner
Posts: 564
Joined: Sun Jul 20, 2008 4:24 pm

Re: Drive components for electric locos and EMUs

Postby Alan Turner » Mon Jul 16, 2018 7:50 am

Also have you considered the High Level option: http://173.254.28.51/~highlev3/chris/Pa ... rpage.html

or the Bull Ant: http://www.hollywoodfoundry.com/bullant%20intro.htm

PS - High Level really need to sort out their web site. Having an IP code as their address means it never comes up on a Google search. They must be loosing a lot of business.

regards

Alan

User avatar
jim s-w
Posts: 1794
Joined: Wed Jul 30, 2008 5:56 pm

Re: Drive components for electric locos and EMUs

Postby jim s-w » Mon Jul 16, 2018 8:12 am

seanmcs wrote:Have a look at the Steam Era Models web site. Based in Melbourne, they sell a Black Beetle powered bogie with the motor and gears in the bogie. I just got one in P4 for conversion of the Dapol GWR diesel railcar. It is not a very powerful motor but might be suitable. I note your first idea uses inexpensive products, so at somewhat over AUD 100 including postage, the BB may be too pricy.

Sean


Or sell Guy your Dapol drive bogie as the wheelbase he needs ;) . There must be lots of US drive mechanisms that have the right wheelbase too.

Jim

User avatar
grovenor-2685
Posts: 3335
Joined: Sun Jun 29, 2008 8:02 pm

Re: Drive components for electric locos and EMUs

Postby grovenor-2685 » Mon Jul 16, 2018 10:25 am

Alan Turner wrote:A
PS - High Level really need to sort out their web site. Having an IP code as their address means it never comes up on a Google search. They must be losing a lot of business.
regards
Alan

Just searched for 'highlevelkits on Google and it came up OK, http://www.highlevelkits.co.uk
Regards
Regards
Keith
Grovenor Sidings

Alan Turner
Posts: 564
Joined: Sun Jul 20, 2008 4:24 pm

Re: Drive components for electric locos and EMUs

Postby Alan Turner » Mon Jul 16, 2018 3:34 pm

grovenor-2685 wrote:
Alan Turner wrote:A
PS - High Level really need to sort out their web site. Having an IP code as their address means it never comes up on a Google search. They must be losing a lot of business.
regards
Alan

Just searched for 'highlevelkits on Google and it came up OK, http://www.highlevelkits.co.uk
Regards


Must be me then but it doesn't show www.highlevelkits.co.uk it says http://173.254.28.51/~highlev3/chris/Pages/

nigelcliffe
Posts: 558
Joined: Mon Jul 21, 2008 8:31 am

Re: Drive components for electric locos and EMUs

Postby nigelcliffe » Mon Jul 16, 2018 5:54 pm

There are some N20 designs with the final drive folded under the motor. That makes them suitable for transverse mounting in 3mm scale diesels and tank locos, so should also fit transversely in 4mm scale models. That makes the final drive a spur gear, or possibly a Delrin chain drive.

Even if you can't find those gearbox/motors with a 12v motor fitted, the 5v and 12v motors are interchangeable.

(I first saw the idea in the 3mm Society Magazine).

- Nigel

User avatar
zebedeesknees
Posts: 102
Joined: Mon Jul 12, 2010 5:15 pm

Re: Drive components for electric locos and EMUs

Postby zebedeesknees » Thu Jul 19, 2018 2:51 pm

One other thought: would it be worth actually electrifying the conductor rails and picking up from those?


Guy, I have tried this with some success... but. The main problem is getting the pickup shoes to behave. On most of the real things, the shoe beams are attached at each end to the wheel bearing caps, so that they move only with the wheel/axle. This fixes the shoe mount datum to the rail so that the distance is independent of any bogie springing or body roll.

However they are mounted on the model, the shoes need to provide sufficient pressure to maintain contact (of course!), but not so much as they cause any detectable roll in the bogie frame or the vehicle itself. They need to drop freely below the height of the conductor rail head, but only as far as the centres of the ramps or they will hit running rails at crossings.

For my experiments I used Bedford sprung bogies (of course again) and found them much more likely to roll than rigid ones. That wouldn't be so bad, but they roll the other way when the conductor rail changes sides. So the upward spring pressure from the shoes needs to be quite a bit less than the downward spring pressure on the primary suspension. I found that to get a suitable spring rate I could solder some 1/16" pb pickup strip to the inside wall of the bogie, running transversely and then bending back across the bogie in a long U, with the shoe, filed from some rail section, on the same side as the soldering. A 'drop stop' from wire was then soldered to the same place, and bent to adjust. I found flat strip to be preferable over wire, as it holds the shoe in contact in the fore-aft direction; it oscillated horribly with a single wire!

This makes the bogie frame live to the conductor rail. Insulated pickups on the wheel treads provide the return path. On an MU any bogie without shoes could be shorted to the wheels, one side or both sides, but the latter would short the running rails. If that isn't an issue, the feature could be used for train detection.

I found that just two shoes on each side of a single unit provided much more reliable pickup than from wheels, even sprung ones, because a scraping pickup is more reliable than a rolling one, scraping crud off rather than collecting it.

Ted.

User avatar
Guy Rixon
Posts: 701
Joined: Sun Mar 27, 2011 6:40 pm

Re: Drive components for electric locos and EMUs

Postby Guy Rixon » Sat Jul 21, 2018 12:32 pm

Ted, thanks for that. It sounds encouraging. Since my electrified lines will have positive and negative conductor rail, I could skip all pick-ups on wheels which would be good.

User avatar
zebedeesknees
Posts: 102
Joined: Mon Jul 12, 2010 5:15 pm

Re: Drive components for electric locos and EMUs

Postby zebedeesknees » Sat Jul 21, 2018 2:34 pm

Indeed Guy, and I have an untried idea for neggy rail pickups - a brass drawing pin. The dome shape should work smoothly on ramps, and it can be larger than proto to make sure it stays on the rail as it won't be visible. The pin part could ride in a piece of brass tube with the conductor wire fitted to the end forming a drop stop. Spring should not be necessary.

Ted.


Return to “Guy Rixon”

Who is online

Users browsing this forum: No registered users and 1 guest