Tender CSBs and motor torque

bobwallison
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Tender CSBs and motor torque

Postby bobwallison » Mon Jan 25, 2021 11:05 pm

I'm about to embark on the conversion of a Bachmann 2MT and am planning on fitting the motor in the tender with a cardan shaft to the loco. I am very tempted by the Lanarkshire Models chassis kit but am a little concerned about possible side-to-side rocking due to the torque from the motor acting on the inside bearing CSBs.

Does anyone have experience of such a set-up? Any comments much appreciated.

Bob

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Will L
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Re: Tender CSBs and motor torque

Postby Will L » Mon Jan 25, 2021 11:48 pm

I think its fair to say that the torque must cause the tender chassis to lean sideways a little bit. But assuming your chassis is acceptably free running and all the reduction gearing is all at the loco end of the drive shaft i doubt it will do it enough to be visibly detectable. It will lean one way going forward and the other going back so it shouldn't oscillate. Which CSBs aren't prone to anyway as the friction between spring wire and fulcrums, and axle blocks and the hornblock they run in, is enough to dampen out any tendency to oscillate.

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Winander
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Re: Tender CSBs and motor torque

Postby Winander » Tue Jan 26, 2021 2:47 am

In S4 News 201 and 202 Steve Duckworth documents the building of three Caledonian engines with motors in the tender. They all used CSBs.
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grovenor-2685
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Re: Tender CSBs and motor torque

Postby grovenor-2685 » Tue Jan 26, 2021 11:42 am

I do remember a suggestion being made in relation to the P4/Studiolith 2:1 gearboxes that 2 shafts could be used, one rotating in each direction. It meant using two such gearboxes,and I doubt anyone tried it.
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Will L
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Re: Tender CSBs and motor torque

Postby Will L » Tue Jan 26, 2021 12:18 pm

Winander wrote:In S4 News 201 and 202 Steve Duckworth documents the building of three Caledonian engines with motors in the tender. They all used CSBs.

Yes I think this is Steve's standard approach and his stuff runs beautifully.
Do remember that if you have a tender drive with a nice big motor in the tender and the loco chassis drive chain jams solid, even a rigid chassis tender may start revolving around the drive shaft, but that hasn't stopped many people getting good results from tender drives.

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Winander
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Re: Tender CSBs and motor torque

Postby Winander » Tue Jan 26, 2021 1:16 pm

This is also relevant regarding the orientation of the universal joints on cardan shafts viewtopic.php?f=89&t=6907#p74699

Plus details of the build of more tender driven locos.
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Dave Holt
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Re: Tender CSBs and motor torque

Postby Dave Holt » Tue Jan 26, 2021 2:01 pm

Will L wrote:if you have a tender drive with a nice big motor in the tender and the loco chassis drive chain jams solid, even a rigid chassis tender may start revolving around the drive shaft


Shades of Wallace and Gromit's a Grand Day Out.
Dave.

bobwallison
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Re: Tender CSBs and motor torque

Postby bobwallison » Tue Jan 26, 2021 6:23 pm

Thanks for the response gents. Looks like I'll be ordering a chassis kit (or two) fairly soon now.

It also seems that I should set up my own little database of Really Useful Articles, mainly from S4 News and MRJ. Can't believe that I overlooked such a useful one as Steve Duckworth's.

Bob

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Winander
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Re: Tender CSBs and motor torque

Postby Winander » Tue Jan 26, 2021 9:02 pm

Bob,

There are a few indeces here https://www.scalefour.org/resources/indices.html. You should be able to do 'control f' searches if you have software to open the spreadsheets.

Searchable MRJ index https://www.modelrailwayjournal.com
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davebradwell
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Re: Tender CSBs and motor torque

Postby davebradwell » Wed Jan 27, 2021 9:41 am

Sorry, I thought I posted yesterday but clearly failed somehow.

All my tender engines have motors in the tender and only one has inside frames - an A1 Pacific. The problem isn't the tender leaning but it wobbles at speed. This is probably a combination of slight out of balance of the motor and variations in torque required by the loco. It's important to make the tender quite heavy because this will require stiffer springs and these will oppose any tendency to lean. It's easy enough to slot brass outside tender frames for p-p brgs and put your springs here but I suspect you'll be fine with the inside frames given the above precaution. If the chassis puts the springs at 00 width you might want to widen them. Keep to a low gear ratio so that the motor revs are low to avoid wobble.

Please use the correct 2 universal joints and the shafts should all be roughly in line at rest.

Don't mount your motor rigidly - I use several layers of double sided tape but there's sticky pads or even bath sealant - to keep it quiet and it should be a great runner.

DaveB
Last edited by davebradwell on Wed Jan 27, 2021 1:21 pm, edited 1 time in total.

essdee
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Re: Tender CSBs and motor torque

Postby essdee » Wed Jan 27, 2021 10:45 am

Dave,

To avoid confusing folk, please would you provide the precise references/photos/drawings in my articles in SN 201/2 that apparently suggest using a single universal joint, as you have implied?

Thank you,

Steve

PS On motor mounts; I have found even my rubber-lined motor cradle arrangement still leaves the Mashima/Tenderiser unit a tad noisy, and am experimenting with stiffening the etched gearbox to reduce 'chatter' a bit more. The jury is out.......

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Re: Tender CSBs and motor torque

Postby davebradwell » Wed Jan 27, 2021 11:19 am

Oops, very sorry, that looks very sound to me. I obviously hadn't checked and was relying on memory so now have the problem of finding what I was remembering. They're not even compensated so I was way off. Didn't intend to cause any upset but there has been a few examples with single u/j creeping back in recently.

I suspect the noise from the tender gearbox to which you refer is just a fundamental result of putting gears on the higher revving part of the drivetrain but yes, stiffening the box should help. It may not be necessary on the BR 2MT with its high footplate.

Humble apologies, Steve and I'll take the broader hint. It was a silly error to make late at night which I just repeated the next day.

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davebradwell
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Re: Tender CSBs and motor torque

Postby davebradwell » Wed Jan 27, 2021 1:22 pm

...and have removed the inaccurate offending bit from my post.

DaveB

essdee
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Re: Tender CSBs and motor torque

Postby essdee » Wed Jan 27, 2021 1:41 pm

Thanks Dave - much appreciated - and no problem!

I, too, have fallen for a late-night mis-appreciation before..... so easy to do. I do think brain-fade plays an increasing part as we move through the years, all too fast.

I am literally in the middle of assembling a CSB tender chassis for one of a pair of SDJR small 4-4-0s today! I am grateful to you and Will for the recent advice about the heavy/stiffish CSB in the tender to counter any tendency to tip. One of the reasons I go overboard on de-burring, bevelling and polishing all rotating mechanism components, is so I can always get a chassis that, with gearbox and rods on, rolls freely when I tip the test plank. If not, I know it 'has the brakes on', and is not ready to receive the motor. With a heavy/stiff tender, and a nice loose-limbed loco mech, even if heavy. the tender tilt reaction will hopefully be minimised. My pre-Group short trains, even of etched brass carriages, should not be a problem, I hope.

Single UJ's...?? I can't recall those anywhere, sorry.....

Cheers,

Steve

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PeteT
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Re: Tender CSBs and motor torque

Postby PeteT » Wed Jan 27, 2021 2:11 pm

Dave I think it is Mike Ainsworth's article in 217 (p27-29) you're thinking of?

Back to the OP I have a similar plan forming, so keep us posted if you go down this route. There is an MRJ article on the Ivatt 4 Brassmasters/Bachmann build including a tender motor. That tender underframe is outside bearing though (but not available separately, I've asked that question...) so doesn't particularly answer the question.

To pick up on another point Dave made, the Lanarkshire underframes are marketed for EM/P4 so not done to 00 spacing. It is something to keep in mind if trying to later expand the theory using the likes of Comet or London Road tender underframes though.

davebradwell
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Re: Tender CSBs and motor torque

Postby davebradwell » Wed Jan 27, 2021 3:09 pm

Yes, Mike Ainsworth's article was noted but there's an older one, best forgotten now. The Ivatt 4 was Chris Pendlenton's in MRJ 175 - it's still running.

DaveB

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Will L
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Re: Tender CSBs and motor torque

Postby Will L » Wed Jan 27, 2021 4:10 pm

davebradwell wrote:...The problem isn't the tender leaning but it wobbles at speed...

What ever else you thing of them, one advantage of CSBs over individually sprung axles is that they should be less inclined to do this.

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Mike Garwood
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Re: Tender CSBs and motor torque

Postby Mike Garwood » Wed Jan 27, 2021 7:54 pm

I've often thought about putting a significant motor in the tender. One of the draw backs as I saw it, was the width of the chassis it was being attached to. If the tender chassis was wider, it would not be able to rock, even with stiffer wires running thru it.
So rather than using a sub chassis, with an inner chassis, why not just use one wider chassis - full stop. I designed a tender chassis - with CSB's - for my next Brit (and last one), to put this theory to the test. Now I can't claim that this was wholly my idea, I had had chats with Justin Newitt regarding this. In fact, I think Justin has a tender that is already built with this system. And it's probably Justin who should take credit for the idea.

So, I had some etches done from my CAD drawing and distributed these to people who had shown an interest...problem is, it's such a long time elapsed, I can't remember who I gave them to!

Anyway, here's the file. And if anyone wants to own up having one of these etches I'd be grateful...just to know if the idea worked or not. Unless, of course, it's sitting on your shelf of shame.

Comments welcome as always.

br tender.docx


Stay safe

Mike

BR tender OS spring v2.dwg
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davebradwell
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Re: Tender CSBs and motor torque

Postby davebradwell » Thu Jan 28, 2021 9:30 am

WillL, the reason my tender wobbles is because it has an 1833 motor mounted high up, lead lining the sides, springs close together and it's doing a scale 80. There is no reason why separate springs should be more inclined to wobble than a csb - none of my other models do this. In fact if they are curved upwards there would be more friction damping than your straight spring.

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bobwallison
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Re: Tender CSBs and motor torque

Postby bobwallison » Thu Jan 28, 2021 12:19 pm

Dave: thanks for the input and your comments on the cardan shaft are noted. A question though - if you use pin point bearings in slots in the outer frames, does that mean there is no sideplay on any of tender wheels? How does that work around curves?

Richard - thanks for the links to those indeces. They are very useful if you can remember the author or the title of the article but searching for "csb" or even "spring" doesn't return the wealth of information availabe in either S4News or MRJ. And searching for "layouts that I find inspiring" is a non-starter, so I think a simple, personalised list is the way to go.

Pete, happy to keep folks posted, but don't hold your breath or expect anything earth-shattering. Current thoughts are csb throughout, sprung axle in the pony truck, cardan shaft above the footplate (because the cab is fully enclosed so the shaft will be almost invisible). I'll make my own frames and use LMS's coupling rods, Gibson's valve gear and Brassmaster's pony truck. And top of the list - move the backhead forward! Bachmann have pushed it so far into the cab that our poor driver and fireman have to stand on the fall plate. I am perplexed that none of the articles or reviews of the model mention this.

Bob

Rdunning
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Re: Tender CSBs and motor torque

Postby Rdunning » Thu Jan 28, 2021 3:28 pm

I've made nine locos with the motor in the tender, admittedly all the tenders have compensated chassis except for one which is CSB suspended, and some have wheelsets which are not perfectly concentric or not mounted at a true perpendicular to the axle, so they do wobble a bit for those reasons but not by virtue of the way they are configured.
For what it's worth I avoid using spur gears revolving at motor speeds in step-down gearboxes or the like if at all possible as I have found they generate too much noise. It's preferable to have the drive shaft running in as near to a straight line as possible as Dave B states above.

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PeteT
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Re: Tender CSBs and motor torque

Postby PeteT » Thu Jan 28, 2021 4:49 pm

bobwallison wrote:A question though - if you use pin point bearings in slots in the outer frames, does that mean there is no sideplay on any of tender wheels? How does that work around curves?


I've built one of Dave's tenders for a J39. I used a 1mm axle with 2mm/1mm sleeve for the middle wheelset. This certainly wasn't an original idea, but works well.

Sounds like an interesting build! One thing to note with the Brassmasters pony is that (edit - the first 10 of) the LMS class 2 2-6-0 needs the swing link version, I've done an etch which is available via Justin at Rumney models which covers this (in addition, not replacement, to the Brassmasters part).
viewtopic.php?f=135&t=6252

The cab modifications sound beneficial.

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Re: Tender CSBs and motor torque

Postby Dave Holt » Thu Jan 28, 2021 9:18 pm

Peter,
I don't think you are right about the swing link truck. Although the 2-6-2 tanks had a swing link at the front and a spring side control truck at the rear, the 2-6-0s (both class 2 and 4) had spring control trucks, as shown in these part photos, both taken from the OPC book - Power of the LMS 2-6-0s and credited to M Mensing and C R L Coles/Rail Archive Stephenson, respectively.
2-6-0_trucks.jpg

2-6-0_trucks1.jpg

Every other photo I've checked, where the truck is visible in the gloom under the buffer beam, confirms the spring control truck.
I'm not sure where the idea that these locos used a swing link truck comes from but i notice the statement is repeated in the new Book of the Ivatt 2-6-2 tanks.
Dave.
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PeteT
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Re: Tender CSBs and motor torque

Postby PeteT » Thu Jan 28, 2021 9:43 pm

Hi Dave,

I was looking through the Irwell book of the 2-6-0s. The wording says swing link and says no more about it, and the majority have spring control trucks as you say from photo evidence. However the first 10, as it goes through the class members, do have swing links.

Edited to add snippet, credited to rail-online:
20210128_214633.jpg


Cheers,
Pete
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Dave Holt
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Re: Tender CSBs and motor torque

Postby Dave Holt » Thu Jan 28, 2021 10:11 pm

No arguing with that.
Dave.


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