Singles and suspension

Michael Waldron
Posts: 14
Joined: Tue Jan 30, 2018 11:01 am

Singles and suspension

Postby Michael Waldron » Fri May 10, 2019 7:54 am

I don’t quite know where there is any reference to Single driver locos in these threads, so I am posting one to ask.

Is there anyone out there who has gone through the thorny issue of how to ‘suspend’ a 2-2-2?
I am an LB&SCR modeller, and have to produce at least 3 2-2-2s.

I have all but ruled out CSBs, as a solitary driven axle doesn’t bode well with them, tending to gravitate towards Iain Xxx’s original SECR 0-4-4 H class in which he used the principle of levers to get the trailing bogie to ‘lever’ up the rear coupled axle.
The way I do it is to have the trailing axle to do the same, with double beams bearing in the driving and trailing axles, with the crucial pivot well towards the driving axle, giving something like 4:1 mechanical advantage.

The leading axle is set to rock on an adjustable pivot screw.
The experience of a fellow member of the Brighton Circle also suggests that Mike Sharman’s Weighted tender would greatly assist what will probably be minimal traction.

Any comments anyone?

Mike

FCA
Posts: 54
Joined: Wed Jul 23, 2008 2:49 pm

Re: Singles and suspension

Postby FCA » Fri May 10, 2019 9:02 am

Can I point you to Barry Luck's seminal articles in MRJs 18 & 19 on split frames wherein he described his solution to the traction problems in building, if memory serves, a Brighton G 2-2-2.

As for the Chatham H I use twin beams on the drivers and have the bogie pivot as the third leg. The bogie itself is either compensated or sprung.

Hope that helps.

Richard

davebradwell
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Joined: Fri Jan 18, 2019 3:48 pm

Re: Singles and suspension

Postby davebradwell » Fri May 10, 2019 9:34 am

Can't see how hanging the tender on the back will help adhesion as it only increases weight on trailing axle. You'd need a strange cantilever to reach the centre.

You want loco as heavy as poss so motor goes in tender with thin wire shaft across cab floor. Spring loco like full size with wire leaf springs each with adjusting screw so you can fiddle with the weight distribution until you reach optimum compromise between staying on track and load haulage. With compensation this distribution is designed in and it takes a re-build to change it.

I always use this approach and it always works and although I've never built a 2-2-2 isn't it like an adjusted 0-6-0? Very few believe me, however and you will receive an onslaught from those who can only think of compensation and another from the csb lot and none of it adjustable. The sprung solution will be quieter.

If leading/trailing wheels are same size you can drive it like a motor bogie - drive one axle and spur gears to other. Hmm!

Have a pleasant experience, whatever.

DaveB

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Will L
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Re: Singles and suspension

Postby Will L » Fri May 10, 2019 12:04 pm

Michael Waldron wrote:I have all but ruled out CSBs, as a solitary driven axle doesn’t bode well with them...

Why?

I know that conventional wisdom on CSBs has suggested in the past that you need the centre of three axles slightly softer than the outer two to prevent porpoising (rocking around the centre axle) but experience is suggesting we worried about that rather too much, as the friction between axle block and horn guide is enough to dampen the system and prevent it happening.

In the past I have played with the idea of implementing a 2-2-2 with very little weight on the outer axles so all the adhesive weight is on the centre one, and thus achieving quite remarkable load hauling feats for a single driver. The trick would be to have the loco rigidly connected to the tender horizontally. Think wheelbarrow. What you are really implementing is an 0-2-0 with the maximum loco weight available for adhesion, and the connection to the tender preventing the loco from pitching back and forth.

Realistically you would probably go for a weight distribution of say 50% on the driver and 25% on each carrying axle. These days, my version of the CSB spread sheet will now allow you to implement any reasonable weight distribution, so the real P4 modellers amongst us can get the loco weight distribution right too!

The hard bit is arranging that the fulcrum connections from axle to the CSB wire are all exactly the right length as this is fairly critical to getting the weight distribution you've planned out of the system. Easy enough when all the wheels are the same size and you can use something like the Highlevel Fulcrum tags all etched to a consistent dimension, but more complicated when you’re trying to support wheels of different sizes from the same CSB wire. I am currently working on the chassis for a GER F6 2-4-2 which will have all wheels connected to the CSB wire. I have now sorted out in my head a kitchen table method of ensuring the length of the axle fulcrums for the carrying wheels is correct and consistent. Thus avoiding the herculean feats of measurement needed to consistently manufacture a series of small parts to very fine tolerances that our more engineering literate brothers would go in for. The F6 will also feature radial trucks which is another, but connected, story.

If you really must stick with compensation, I would have thought you should go with double beams along the frames one side of the driver and a single beam in the centre on the other side. So all three rest on the driving axle. These beams, which would presumably be stepped, should be identical and would give equal weight distribution on front and back axles. A pivot point 1/3 of the way along each beam from the driver would give a 25% 50% 25% weight distribution, assuming you get the centre of gravity over the driving axle. I've tried to think about what might happen if you wanted to putting tender weight into a compensated system but I'm afraid my head is still hurting.

I'm with Dave in thinking a motor in the tender and lead in the boiler is probably the way to go.

Should you actively consider a CSB, I would be quite happy to have a further chat about the best way to do it.

Michael Waldron
Posts: 14
Joined: Tue Jan 30, 2018 11:01 am

Re: Singles and suspension

Postby Michael Waldron » Sat May 11, 2019 5:57 am

FCA wrote:Can I point you to Barry Luck's seminal articles in MRJs 18 & 19 on split frames wherein he described his solution to the traction problems in building, if memory serves, a Brighton G 2-2-2.

As for the Chatham H I use twin beams on the drivers and have the bogie pivot as the third leg. The bogie itself is either compensated or sprung.

Hope that helps.

Richard

Thanks Richard. Barry is a fellow Brighton Circle member, and has advised on the matter, as well as offering advice on his website. (Well worth a look)
I wondered whether there would be more ideas out there, especially with regard to CSBs
Mike

Michael Waldron
Posts: 14
Joined: Tue Jan 30, 2018 11:01 am

Re: Singles and suspension

Postby Michael Waldron » Sat May 11, 2019 6:29 am

davebradwell wrote:Can't see how hanging the tender on the back will help adhesion as it only increases weight on trailing axle. You'd need a strange cantilever to reach the centre.

You want loco as heavy as poss so motor goes in tender with thin wire shaft across cab floor. Spring loco like full size with wire leaf springs each with adjusting screw so you can fiddle with the weight distribution until you reach optimum compromise between staying on track and load haulage. With compensation this distribution is designed in and it takes a re-build to change it.

I always use this approach and it always works and although I've never built a 2-2-2 isn't it like an adjusted 0-6-0? Very few believe me, however and you will receive an onslaught from those who can only think of compensation and another from the csb lot and none of it adjustable. The sprung solution will be quieter.

If leading/trailing wheels are same size you can drive it like a motor bogie - drive one axle and spur gears to other. Hmm!

Have a pleasant experience, whatever.

DaveB


Dave:
Thanks for those thoughts.

That was one approach I was going to use, when I had an adjustable gearbox etched a couple of years ago when I ran E.B.Models (now with another Brighton Circle member), with tender drive gear 2:1 reduction frame. I just haven’t got round to fitting it yet.
So there are two options at least. Maybe a third when I’ve read Will’s response!

Mike

Michael Waldron
Posts: 14
Joined: Tue Jan 30, 2018 11:01 am

Re: Singles and suspension

Postby Michael Waldron » Sat May 11, 2019 6:46 am

Will L wrote:
Michael Waldron wrote:I have all but ruled out CSBs, as a solitary driven axle doesn’t bode well with them...

Why?

I know that conventional wisdom on CSBs has suggested in the past that you need the centre of three axles slightly softer than the outer two to prevent porpoising (rocking around the centre axle) but experience is suggesting we worried about that rather too much, as the friction between axle block and horn guide is enough to dampen the system and prevent it happening.

In the past I have played with the idea of implementing a 2-2-2 with very little weight on the outer axles so all the adhesive weight is on the centre one, and thus achieving quite remarkable load hauling feats for a single driver. The trick would be to have the loco rigidly connected to the tender horizontally. Think wheelbarrow. What you are really implementing is an 0-2-0 with the maximum loco weight available for adhesion, and the connection to the tender preventing the loco from pitching back and forth.

Realistically you would probably go for a weight distribution of say 50% on the driver and 25% on each carrying axle. These days, my version of the CSB spread sheet will now allow you to implement any reasonable weight distribution, so the real P4 modellers amongst us can get the loco weight distribution right too!

The hard bit is arranging that the fulcrum connections from axle to the CSB wire are all exactly the right length as this is fairly critical to getting the weight distribution you've planned out of the system. Easy enough when all the wheels are the same size and you can use something like the Highlevel Fulcrum tags all etched to a consistent dimension, but more complicated when you’re trying to support wheels of different sizes from the same CSB wire. I am currently working on the chassis for a GER F6 2-4-2 which will have all wheels connected to the CSB wire. I have now sorted out in my head a kitchen table method of ensuring the length of the axle fulcrums for the carrying wheels is correct and consistent. Thus avoiding the herculean feats of measurement needed to consistently manufacture a series of small parts to very fine tolerances that our more engineering literate brothers would go in for. The F6 will also feature radial trucks which is another, but connected, story.

If you really must stick with compensation, I would have thought you should go with double beams along the frames one side of the driver and a single beam in the centre on the other side. So all three rest on the driving axle. These beams, which would presumably be stepped, should be identical and would give equal weight distribution on front and back axles. A pivot point 1/3 of the way along each beam from the driver would give a 25% 50% 25% weight distribution, assuming you get the centre of gravity over the driving axle. I've tried to think about what might happen if you wanted to putting tender weight into a compensated system but I'm afraid my head is still hurting.

I'm with Dave in thinking a motor in the tender and lead in the boiler is probably the way to go.

Should you actively consider a CSB, I would be quite happy to have a further chat about the best way to do it.


Will:
Thanks for that.
Hmm. The real question is “do I have enough confidence that I could get the vertically rigid tender coupling working smoothly enough to enable both weight bearing down as well as pivoting as needed? And at that scale?”

I had simply ruled CSBs out because of the same argument you presented at the outset of your piece.
All Stroudley’s locos were softer sprung on the centre axle.

I’m also mindful of the recent article in S4News suggesting greater pressure on the outer axles by adjusting the compensation pivot centre outwards, to avoid derailing! Presumably this has the same effect as softer centre CSB distance between fulcrums. (Or should that be fulcra? Latin neuter plural?!!)

As you rightly suggest, the leading and trailing wheels of Stroudley’s G class 2-2-2s were 4’ 6” and the drivers 6’ 6”, so a fair difference to cope with.
I etched some CSB fittings similar to HL’s to fit over the hornblock tubular extension with varying height, particularly to cope with the 0-4-2 D1 tanks which have 5’ 6” drivers and 4’ 6” trailing wheels also.
I have also had some detachable springs etched to go round the hornblocks - MJT and HL types - so wheels san be dropped out, so there would be competition with needing to fit CSB parts as well!

I think this calls for a test chassis!

Thanks
Mike

billbedford
Posts: 682
Joined: Tue Oct 02, 2012 2:40 pm

Re: Singles and suspension

Postby billbedford » Sat May 11, 2019 7:47 am

With a 3 mm difference in axle centres you should be able to arrange a CBS that goes over the carrying axles and under the driving.
Bill Bedford
Mousa Models
http://www.mousa.biz

JFS
Posts: 666
Joined: Wed Dec 16, 2009 3:47 pm

Re: Singles and suspension

Postby JFS » Sat May 11, 2019 7:52 am

Not done one myself, but faced with the design challenge, I would be tempted to look at driving all three tender axles via spur gears using an adapted diesel loco mechanism - there are planty of them out there. The biggest challenge would be hiding it from view within a pretty sparse tender underframe. Such a solution would leave the driving axle free to fit the working inside motion - it is all a bit visible in there! And given some depleted uranium for ballast, it would have a lot more haulage capability than the real thing ever had!

All that said, Barry's singles work pretty well - why re-invent wheels when the maestro is at hand? Unless the lack of inside motion bothers you...

Looking forward to seeing the outcome of your deliberations - hope you will be posting!

Good luck,

Michael Waldron
Posts: 14
Joined: Tue Jan 30, 2018 11:01 am

Re: Singles and suspension

Postby Michael Waldron » Sat May 11, 2019 8:04 am

billbedford wrote:With a 3 mm difference in axle centres you should be able to arrange a CBS that goes over the carrying axles and under the driving.


Thanks Bill.
Slight diversion - do you have a .pdf you could send me of the instructions of your now withdrawn carriage set couplings? Lost mine
Mike

Michael Waldron
Posts: 14
Joined: Tue Jan 30, 2018 11:01 am

Re: Singles and suspension

Postby Michael Waldron » Sat May 11, 2019 8:09 am

JFS wrote:Not done one myself, but faced with the design challenge, I would be tempted to look at driving all three tender axles via spur gears using an adapted diesel loco mechanism - there are planty of them out there. The biggest challenge would be hiding it from view within a pretty sparse tender underframe. Such a solution would leave the driving axle free to fit the working inside motion - it is all a bit visible in there! And given some depleted uranium for ballast, it would have a lot more haulage capability than the real thing ever had!

All that said, Barry's singles work pretty well - why re-invent wheels when the maestro is at hand? Unless the lack of inside motion bothers you...

Looking forward to seeing the outcome of your deliberations - hope you will be posting!

Good luck,


Thanks Howard;
Just had to cobble together some cosmetic bits for my Single “Sussex”, with outside frames as well as chassis, as the same issue pertained, as well as a similarly outside framed 2-4-0 Belgravia class “Goodwood”.
I’ve drawn up some artwork for an etch, as this will be needed multiple times!

It looks likely Barry May yet win out!

Mike

Rdunning
Posts: 18
Joined: Tue Oct 21, 2008 8:38 pm

Re: Singles and suspension

Postby Rdunning » Sat May 11, 2019 1:11 pm

In MRJ 21 page 55 Allan Sibley described how he arranged the drive for a GWR Dean single. The drive was on the trailing wheel via an intermediate shaft geared to the motor and the "driving" wheel was weighted and allowed to go along for the ride.
This arrangement had the advantages of 1) allowing the tender to be weighted to bear down on the rear of the loco and 2) permitting a gear ratio around 30:1 (it was a Portescap 1219 mechanism).
The suspension was by means of compensation between the fixed rear axle and the leading bogie which was free to pivot in all planes.

IIRC Allan said in the article that the loco was capable of hauling seven bogie vehicles round "Pampisford".

You might want to consider this as a method for your project Mike.

Richard

Michael Waldron
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Joined: Tue Jan 30, 2018 11:01 am

Re: Singles and suspension

Postby Michael Waldron » Sat May 11, 2019 3:51 pm

billbedford wrote:Sorry, I can't send this by PM.

E007-2 Instructions.pdf


Many thanks Bill

Mike

Michael Waldron
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Joined: Tue Jan 30, 2018 11:01 am

Re: Singles and suspension

Postby Michael Waldron » Sat May 11, 2019 4:50 pm

Rdunning wrote:In MRJ 21 page 55 Allan Sibley described how he arranged the drive for a GWR Dean single. The drive was on the trailing wheel via an intermediate shaft geared to the motor and the "driving" wheel was weighted and allowed to go along for the ride.
This arrangement had the advantages of 1) allowing the tender to be weighted to bear down on the rear of the loco and 2) permitting a gear ratio around 30:1 (it was a Portescap 1219 mechanism).
The suspension was by means of compensation between the fixed rear axle and the leading bogie which was free to pivot in all planes.

IIRC Allan said in the article that the loco was capable of hauling seven bogie vehicles round "Pampisford".

You might want to consider this as a method for your project Mike.

Richard


Richard:
I confess I hadn’t thought of that option, though I do have the RM article from the 60’s (?) of an alternative drive for a 2-2-2 using model racing car bevel gears linked by a shaft to both front and rear carrying wheels, though it might be problematic with the need for compensation.

Mike

Terry Bendall
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Joined: Sun Jul 27, 2008 7:46 am

Re: Singles and suspension

Postby Terry Bendall » Sun May 12, 2019 8:48 am

Michael Waldron wrote:Barry is a fellow Brighton Circle member, and has advised on the matter, as well as offering advice on his website. (Well worth a look)


It is and the advice on the single can be found at http://www.lbscrmodels.co.uk/sutherland.html There are of course other methods but Barry usually uses the principles advocated many years ago by Mike Sharman. They work. What more do you want? :)

Terry Bendall


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