Tim Humphreys ex Mudhen
Western Thunderer
I'm sure I've seen a photo of 92021 late in life with a BR1G tender, don't know about the others.
Tim
Rebuilt Crosti 9f
- Thread starter spikey faz
- Start date
I'm sure I've seen a photo of 92021 late in life with a BR1G tender, don't know about the others.
Tim
daifly
Western Thunderer
If it's a 'rebuilt' Crosti then a BR1G is fair game for a couple of them for periods of their remaining short lives however, the Scorpio box says a BR1B tender wich some of the class ran with until being scrapped. I confess to missing the comment 'rebuilt' in Mikes opening para but it seems from the thumbnail picture in post#1 that a BR1G has been supplied. My misunderstanding. 92021 and 92023 ended their days with 1G tenders, 92024 had one briefly. The rest of them ended up with a mix of 1B, 1C and 1F tenders.
spikey faz
Western Thunderer
The kit normally comes with a BR1B tender. However, as I've seen pictures of 92021 and 92023 (didn't know about 92024) in rebuilt guise with BR1G tenders I asked the very helpful folk at Scorpio/Seven Models to supply the kit with a BR1G tender.
I just fancied something a bit different I suppose.
Mike
I just fancied something a bit different I suppose.
Mike
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spikey faz
Western Thunderer
We now have a compensated chassis. Twin beams to avoid the waterscoop.
I've also amended one of the hatch doors as it appeared to be hinged from the wrong side. I've got a crude representation of the catch, but hinges yet to be added. I wasn't going to bother but it's a bit visible...
Mike
I've also amended one of the hatch doors as it appeared to be hinged from the wrong side. I've got a crude representation of the catch, but hinges yet to be added. I wasn't going to bother but it's a bit visible...
Mike
simond
Western Thunderer
twin beams are ok, if the third axle is able to rock.
Otherwise, it has 4 legs on the stool, and doesn't properly compensate.
spikey faz
Western Thunderer
That got me thinking and you are of course correct. Duh! Why didn't I think of that? Anyway, I shall be taking steps to right this. Thanks.
In the meantime the following link provides some interesting reading (wish I'd read this first!).
Scalefour Digest 41.0 'The principles of model locomotive suspension'
Mike
Eastsidepilot
Western Thunderer
Two beams that work independently of each other might be better then the third axle does not have to rock.
spikey faz
Western Thunderer
T
On the subject of compensation I am now having a look at the loco chassis. The kit provides parts for a kind of twin beam compensation. I'm in two minds about this but I think I'll end up going with it.
Mike
Both beams are independent of each other. I am however modifying the third axle to pivot. Initial results are encouraging and much smoother. The guidance in the link I provided does suggest this set up for 6 wheel tenders, so it should be OK.
On the subject of compensation I am now having a look at the loco chassis. The kit provides parts for a kind of twin beam compensation. I'm in two minds about this but I think I'll end up going with it.
Mike
richard carr
Western Thunderer
Mike
In the Mike Sharman book on compensation, there is a diagram for how to do a 2-10-0 chassis, but I recall that it was seriously complicated.
In the MOK kit the chassis uses independent beams on each pair of outer wheels and a sprung centre wheel. I haven't got round to testing this yet but it should work well enough. My DJH 9f uses beams on the outer wheels and a centre rocking axle, it runs just fine, the shorting on the brakes was far more of a problem going round corners. Now it is battery powered so that doesn't matter any more.
MOK do plastic brake blocks I would see if you can get a set if your kit doesn't have them, the clearances are very tight.
Richard
In the Mike Sharman book on compensation, there is a diagram for how to do a 2-10-0 chassis, but I recall that it was seriously complicated.
In the MOK kit the chassis uses independent beams on each pair of outer wheels and a sprung centre wheel. I haven't got round to testing this yet but it should work well enough. My DJH 9f uses beams on the outer wheels and a centre rocking axle, it runs just fine, the shorting on the brakes was far more of a problem going round corners. Now it is battery powered so that doesn't matter any more.
MOK do plastic brake blocks I would see if you can get a set if your kit doesn't have them, the clearances are very tight.
Richard
simond
Western Thunderer
Doesn’t work, Col. (Well, it’ll work, but it ain’t equalised) assuming the two beams are independent, each one puts a support point above the respective rail, half way between the two wheels. The other axle puts another support point above each rail, so you have two supports each side and like a four legged stool, it’ll rock. If you allow the third axle to rock, you reduce two of the support points to one, and like a three legged stool, it’s stable, provided the centre of gravity is always inside the triangle drawn through the three support points.
on a 10 wheel chassis, I’d be inclined to cheat. A pair of independent beams on the rear axles leaves space for the gearbox, a single beam for the front 2 axles gives 3 support points. And I’d spring the middle one.
Ballast to the rear so the CoG is always inside the triangle and Robert’s your mother’s brother.
CSB might be a good solution, though I’ve never done one.
Ian@StEnochs
Western Thunderer
I find in 7mm scale that Individual coil springs on each axlebox work well and are very easy to install. On the odd time that I have tried compensation beams it's been a bit less straightforward.
Ian.
Ian.
simond
Western Thunderer
All but one of my locos is either compensated and sprung. I’m not convinced that one is much better than the other, except for my Tre Pol & Pen, where some fiddling with springing and in particular, spring rates, made a phenomenal difference to the haulage capability.
The one, it was the first I built in 7mm, a Springside 45xx, some 25 years ago. I purchased the jointed rods & hornblocks, and have a new motor-gearbox I have the tools and the skills (more or less). I could do with more time and much more mojo..
I quite like the idea of the CSB. Might try it.
The one, it was the first I built in 7mm, a Springside 45xx, some 25 years ago. I purchased the jointed rods & hornblocks, and have a new motor-gearbox I have the tools and the skills (more or less). I could do with more time and much more mojo..
I quite like the idea of the CSB. Might try it.
SimonT
Western Thunderer
I've always felt that this three point suspension thing is a red herring. As part of my evidence may I give you the Reliant Robin? You cannot call them a stable vehicle.
The problem is that any long and narrow wheel base vehicle is easily upset by a rolling moment about the lonitudinal axis, particularly if the axis for the resulting moment of inertia is a long way out of the plane of contact. As an exagerated example , look at those scarry airliner cross wind landing videos where the clown doing the driving lets the upwind wing rise. This generates a large rolling moment about the two points of contact, the nose wheel and the down wind main wheelset, which then imparts a yawing moment. Ok, with the aircraft we are talking of large forces compared with a toy train but the principle of the system is the same, even if the point of contact is different.
We go mad to install three point suspensions on locomotives but leave other vehicles with all kinds of mongrel systems; bogie vehicle suspension anyone? Finally may I ask you to consider the Morgan three wheelers? (The proper one's not the modern pastiche) Why do they have a reputtion for stability?
Now I've said Jehovah and shall run away before the shoes and rocks come my way!
Simon
PS I would spring all locos if I could find a range of suitable springs that have a choice of springs rates and sizes.
The problem is that any long and narrow wheel base vehicle is easily upset by a rolling moment about the lonitudinal axis, particularly if the axis for the resulting moment of inertia is a long way out of the plane of contact. As an exagerated example , look at those scarry airliner cross wind landing videos where the clown doing the driving lets the upwind wing rise. This generates a large rolling moment about the two points of contact, the nose wheel and the down wind main wheelset, which then imparts a yawing moment. Ok, with the aircraft we are talking of large forces compared with a toy train but the principle of the system is the same, even if the point of contact is different.
We go mad to install three point suspensions on locomotives but leave other vehicles with all kinds of mongrel systems; bogie vehicle suspension anyone? Finally may I ask you to consider the Morgan three wheelers? (The proper one's not the modern pastiche) Why do they have a reputtion for stability?
Now I've said Jehovah and shall run away before the shoes and rocks come my way!
Simon
PS I would spring all locos if I could find a range of suitable springs that have a choice of springs rates and sizes.
spikey faz
Western Thunderer
Or maybe I'll go for a rigid chassis!! 
But thank you all for your ideas. I'm still not sure yet. If I use the beam system that comes with the kit it does appear to be relatively straightforward to remove if it doesnt do what I want it to.
In the meantime I've started to emboss the frame rivets.
Mike
But thank you all for your ideas. I'm still not sure yet. If I use the beam system that comes with the kit it does appear to be relatively straightforward to remove if it doesnt do what I want it to.
In the meantime I've started to emboss the frame rivets.
Mike
simond
Western Thunderer
The difference between a Morgan 3-wheeler and a Reliant Robin is the relation of CoG to the triangle, and it’s height relative to the road. there are a few other factors to complicate matters.
The Morgan is low, the CoG is low and nearer the front and it has two wheels at the front.
The Robin has a single point at the front, and a very weight-forward design, and like all road vehicles, generates its steering forces at the front tyre contact patch, which coupled with braking forces (I guess old cross ply tyres, we‘re in the range of 0.5 to 0.8 g) can cause the thing to either lift a rear wheel, or go the whole hog. And, as you mention with your crosswind landing, the fact that the wheels are not in line causes moments in the other axis, and the castor-action of the steering becomes non existent when one back wheel is way above the road, which confuses the driver. And the driver & passengers form a not-inconsiderable proportion of the overall mass, and passengers in particular start to run around shouting “don’t panic” just when the driver needs to concentrate…
there are lots of “one at the front” designs which work passably well. Piaggio and Bajaj spring to mind, there are millions of them. There’s a YouTube of a near miss with a 3-wheeler van in which it swerves one way, doesn’t fall over by the skin of his teeth, and then swerves the other, rolls from 45 degrees one way to maybe 35 the other, and then settles back down. I hate to think how the contents were. Probably like a DPD van…
Returning to locomotives. If it were battery power, I’d mostly agree, but ensuring electrical contact, particularly in pre DCC days, was vital to any semblance of realism.
”He said ‘Jehovah’!”
”so did you!”
The Morgan is low, the CoG is low and nearer the front and it has two wheels at the front.
The Robin has a single point at the front, and a very weight-forward design, and like all road vehicles, generates its steering forces at the front tyre contact patch, which coupled with braking forces (I guess old cross ply tyres, we‘re in the range of 0.5 to 0.8 g) can cause the thing to either lift a rear wheel, or go the whole hog. And, as you mention with your crosswind landing, the fact that the wheels are not in line causes moments in the other axis, and the castor-action of the steering becomes non existent when one back wheel is way above the road, which confuses the driver. And the driver & passengers form a not-inconsiderable proportion of the overall mass, and passengers in particular start to run around shouting “don’t panic” just when the driver needs to concentrate…
there are lots of “one at the front” designs which work passably well. Piaggio and Bajaj spring to mind, there are millions of them. There’s a YouTube of a near miss with a 3-wheeler van in which it swerves one way, doesn’t fall over by the skin of his teeth, and then swerves the other, rolls from 45 degrees one way to maybe 35 the other, and then settles back down. I hate to think how the contents were. Probably like a DPD van…
Returning to locomotives. If it were battery power, I’d mostly agree, but ensuring electrical contact, particularly in pre DCC days, was vital to any semblance of realism.
”He said ‘Jehovah’!”
”so did you!”
SimonT
Western Thunderer
Simon
Add to the original Morgan the sprung sliding pillar suspension at the front. Overall I suspect that it is the real suspension on the three wheelers that has the biggest effect and that is what we are missing in our toy trains. I suspected that Guy Martin would roll his 'breathed on' Piaggio big time but it only happened on an uneven race track in racing conditions.
The locos on Aberbeeg were a real mixture of suspensions, both sprung and compensated, and we had no problems with things stopping or falling off. I didn't use 'stay a lives' and for the last four shows we gave up cleaning everything. Instead we went to using Rail Zip to ensure good contact' We had tested everything to death until everything worked perfectly every where, included on the uneven track in the yard. That just left the biological factor and I will hold my hand up and admit that I did run trains into points that were set to the opposite route
. We adopted the hold the hand up and "That was me" approach now seen on Premiership Rugby pitches.
I reckon I'm well out of range from your stones on my Welsh Hill. The wind and rain would make them fall well short
Mike,
I'm looking forward to seeing the 9F on those curves!
Simon
Add to the original Morgan the sprung sliding pillar suspension at the front. Overall I suspect that it is the real suspension on the three wheelers that has the biggest effect and that is what we are missing in our toy trains. I suspected that Guy Martin would roll his 'breathed on' Piaggio big time but it only happened on an uneven race track in racing conditions.
The locos on Aberbeeg were a real mixture of suspensions, both sprung and compensated, and we had no problems with things stopping or falling off. I didn't use 'stay a lives' and for the last four shows we gave up cleaning everything. Instead we went to using Rail Zip to ensure good contact' We had tested everything to death until everything worked perfectly every where, included on the uneven track in the yard. That just left the biological factor and I will hold my hand up and admit that I did run trains into points that were set to the opposite route
. We adopted the hold the hand up and "That was me" approach now seen on Premiership Rugby pitches.I reckon I'm well out of range from your stones on my Welsh Hill. The wind and rain would make them fall well short
Mike,
I'm looking forward to seeing the 9F on those curves!
Simon
spikey faz
Western Thunderer
If my Crosti were to be pounding up and down hundreds of miles of Scaleseven track I'd definitely be looking at some sort of sort of high fidelity suspension. Sadly there is insufficient space at Spikey Towers to permit this! 
So, I'm limited to just a few feet of running line. I'm going to try the kit supplied compensation system and see how it goes.
In the meantime I've started reaming out the bearings in the kit to take the slightly larger diameter 5mm axles that MOK use in their driving wheels.
Mike
So, I'm limited to just a few feet of running line. I'm going to try the kit supplied compensation system and see how it goes.In the meantime I've started reaming out the bearings in the kit to take the slightly larger diameter 5mm axles that MOK use in their driving wheels.
Mike
spikey faz
Western Thunderer
spikey faz
Western Thunderer
I started putting the compensation beams together as per the instructions. But I was struggling to get them assembled without any slop where the pivots are. Also I managed to solder one of the pivots up solid! Oops! So I came up with my own design using Slaters crankpin bushes.
Before:
After:
It's not elegant but I think it'll work.
Mike
Before:
After:
It's not elegant but I think it'll work.
Mike