Gibson LMS 2P 4-4-0

davebradwell
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Re: Gibson LMS 2P 4-4-0

Postby davebradwell » Fri Dec 31, 2021 6:44 pm

Most likely reason for things sticking is tiny burrs assuming, of course, you get a decent surface finish on the sliding faces. Sharp corners and edges of a component are easily damaged so it's good practice to break all the corners of a component with a tiny chamfer using either a fine file or form of scraper. Real drawings have a standard note to this effect - ours said "remove all burrs and sharp edges". Ends of holes should always be chamfered slightly - easiest way is with larger drill. You'll find that after this treatment the parts move more smoothly and any remaining tight spots can be dealt with properly.

DaveB

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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Fri Dec 31, 2021 7:03 pm

David Thorpe wrote:... I'm just rebuilding a chassis for a 0-4-4T loco and it isn't going to have a fixed axle, driving or otherwise. I'm currently trying to make up my mind whether to do twin beams on the drivers, or CSB them as an 0-4-0, leaving the bogie to look after itself.

4-4-0s almost always benefit from (need) some loco weight on the bogie. CSB the 2 driving axles (2 axle CSBs are trivial and don't need access to the dreaded spreadsheet) and support the other end on a bogie of your choice so the loco sits level. All (and possibly rather more than ) you need to know on this thread
One problem I've had with hornblocks in the past is their tendancy to stick. Has anyone any ideas as to how that can be avoided or resolved? Obviously one wants the hornblocks to move freely in the hornguides, but at the same time lateral movement should obviously be kept to a minimum.

And again on this thread posted, I notice, 12 years ago now

Daddyman
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Re: Gibson LMS 2P 4-4-0

Postby Daddyman » Sat Jan 01, 2022 11:28 am

Thanks for that link, Will.

Do people find the High Level hornblocks incredibly consistent in terms of concentricity? We're always cautioned to check the concentricity of blocks, and once the inevitable lack of concentricity has been found, to always pair the same block in the same orientation with the same hornway. But I don't find that necessary with the HL blocks - all the ones I've used come out spot on for concentricity (admittedly "only" measuring with a Vernier, albeit a good quality Mitutoyo one). Is this others' experience? What I do find is that the block is stiffer in the hornguide in its "north-south" orientation (if you see what I mean) than it is in its "east-west", suggesting there's some slight tolerance different in the machining of the slot in the block.

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zebedeesknees
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Re: Gibson LMS 2P 4-4-0

Postby zebedeesknees » Sat Jan 01, 2022 11:43 am

Daddyman wrote:Thanks for that link, Will.

Do people find the High Level hornblocks incredibly consistent in terms of concentricity?
What I do find is that the block is stiffer in the hornguide in its "north-south" orientation (if you see what I mean) than it is in its "east-west", suggesting there's some slight tolerance different in the machining of the slot in the block.


Concentric - yes. But I always run a fine triangular Swiss file up the side slots so as to remove any 'rag', and make sure that the bearing has a little freedom in what would be the roll plane, as DaveB mentioned somewhere. A few seconds at this stage can save minutes or hours sorting it later...

Ted.
(A purists' purist)

David Thorpe

Re: Gibson LMS 2P 4-4-0

Postby David Thorpe » Sat Jan 01, 2022 12:01 pm

I'm just making up some HL hornblocks so as to proceed with a CSB installation on my 0-4-4T. They'e not particularly easy, and the most awkward part I've found about them is bending back the horncheeks so that they are absolutely symmetrical and straight. Using the file as suggested in the instructions they did not bend back at all easily and I found that it was small inconsistencies in these horncheeks once I'd bent them back that caused the greatest problems with the bearings then sliding easily in the guides.

I'm also not looking forward to fitting the CSB tags. Past experience has shown that it is a devil of a job trying to open out the hole in the very thin metal of the tag to fit the boss on the bearing. Nor do I like using the the HL CSB jig very much, but I shall persevere. I do sometimes think that the original system as described iun the CLAG site was rather easier - MJT hornblocks, Markits handrail knobs, and a ruler.....

DT

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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Sat Jan 01, 2022 12:31 pm

Daddyman wrote:Thanks for that link, Will.

Do people find the High Level hornblocks incredibly consistent in terms of concentricity? We're always cautioned to check the concentricity of blocks, and once the inevitable lack of concentricity has been found, to always pair the same block in the same orientation with the same hornway. But I don't find that necessary with the HL blocks - all the ones I've used come out spot on for concentricity (admittedly "only" measuring with a Vernier, albeit a good quality Mitutoyo one). Is this others' experience?

I admit I have never found failure of concentricty on HL blocks, but then I haven't really looked. If you match the block to the guide, keep them paired (and always the same way up*), and then fit them to the chassis by use of a jig,any minor errors will be taken care off. Only if the horn guides are etched into the frame (e.g. Bill Bedford's) then you will need to check.
* Then as described in 'that' link the HL blocks need "fettling" so the blocks will end up slightly different widths horizontally and vertically, and potentially less concentric than they started
What I do find is that the block is stiffer in the hornguide in its "north-south" orientation (if you see what I mean) than it is in its "east-west", suggesting there's some slight tolerance different in the machining of the slot in the block.

Also as pointed out somewhere in that thread, the slot does not need to be that close a fit on the grove in the block as it is only the hornguides that must have a close fit and the slot edges just keep the block aligned with the frames.

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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Sat Jan 01, 2022 12:51 pm

David Thorpe wrote:I'm just making up some HL hornblocks so as to proceed with a CSB installation on my 0-4-4T. They'e not particularly easy, and the most awkward part I've found about them is bending back the horncheeks so that they are absolutely symmetrical and straight. Using the file as suggested in the instructions they did not bend back at all easily and I found that it was small inconsistencies in these horncheeks once I'd bent them back that caused the greatest problems with the bearings then sliding easily in the guides.

I've always bent mine up with flat nosed pliers which have nice right angled edges to ensue you bend them by roughly the right amount. I then fettle them vertical but I find this to be the work of moments. N.B. do not be tempted to reinforce with solder at this stage as it will stop the block sliding cleanly.

I'm also not looking forward to fitting the CSB tags. Past experience has shown that it is a devil of a job trying to open out the hole in the very thin metal of the tag to fit the boss on the bearing.
Holding the tag in the fingers across the edges and twirling a round file in it till it fit has always worked for me. Again done is moments

Nor do I like using the the HL CSB jig very much, but I shall persevere. I do sometimes think that the original system as described iun the CLAG site was rather easier - MJT hornblocks, Markits handrail knobs, and a ruler.....

I've done (and documented) it both ways and I'm sold on the Jig. However knowing how to set them out with a ruler is good for the sole and does help you understand what is going on.

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Winander
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Re: Gibson LMS 2P 4-4-0

Postby Winander » Sat Jan 01, 2022 1:55 pm

Will L wrote:
David Thorpe wrote:I'm just making up some HL hornblocks so as to proceed with a CSB installation on my 0-4-4T. They'e not particularly easy, and the most awkward part I've found about them is bending back the horncheeks so that they are absolutely symmetrical and straight. Using the file as suggested in the instructions they did not bend back at all easily and I found that it was small inconsistencies in these horncheeks once I'd bent them back that caused the greatest problems with the bearings then sliding easily in the guides.

I've always bent mine up with flat nosed pliers which have nice right angled edges to ensue you bend them by roughly the right amount. I then fettle them vertical but I find this to be the work of moments. N.B. do not be tempted to reinforce with solder at this stage as it will stop the block sliding cleanly.


Parallel action pliers (Maun) for me, a nice right angle between the gripping surface and the ends. I have also used them to close the horncheeks against the bearing which corrects any twisting in the cheeks and places them close to optimum position.
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David Thorpe

Re: Gibson LMS 2P 4-4-0

Postby David Thorpe » Sat Jan 01, 2022 3:17 pm

Winander wrote:Parallel action pliers (Maun) for me, a nice right angle between the gripping surface and the ends. I have also used them to close the horncheeks against the bearing which corrects any twisting in the cheeks and places them close to optimum position.


II think the problems I have been having may be because I think I have been using slimline ones - I hadn't realised that as all came out of an unmarked packet in my spares box. As the cheeks for these are narrower than those for the standard units, they are clearly more difficult to fold up even when following the instructions to the letter - flat nosed pliers to grip the main etch, and then the horncheeks bent up using a flat needle file applying pressure upwards and sideways simultaneously. Unfortunately the horncheeks proved stubbornly resistant to movement using this method, and when they did eventually move it was not a nice smooth movement and the horncheeksd were left twisted. This had to be corrected as far as possible by further use of the pliers. I've now found a couple of standard units and will use the slimline ones on the gearbox axle, where space is at something of a premium, and the standards on the other one - I assume they can be mixed?

Will L wrote:Holding the tag in the fingers across the edges and twirling a round file in it till it fit has always worked for me. Again done is moments


You must have tougher fingers than me. The tags are made of very thin metal. As you say, to open the hole you have to hold the tag across the edges. Twirling a file? I don't have a suitably sized round file, but I do have a broach and trying to open up the hole using that is extremely uncomfortable on the fingers as the thin metal does its best to slice them open. Not moments, but several very uncomfortable minutes.

DT

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zebedeesknees
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Re: Gibson LMS 2P 4-4-0

Postby zebedeesknees » Sat Jan 01, 2022 5:18 pm

David Thorpe wrote:I'm just making up some HL hornblocks so as to proceed with a CSB installation on my 0-4-4T. They'e not particularly easy, and the most awkward part I've found about them is bending back the horncheeks so that they are absolutely symmetrical and straight. Using the file as suggested in the instructions they did not bend back at all easily and I found that it was small inconsistencies in these horncheeks once I'd bent them back that caused the greatest problems with the bearings then sliding easily in the guides.

I'm also not looking forward to fitting the CSB tags. Past experience has shown that it is a devil of a job trying to open out the hole in the very thin metal of the tag to fit the boss on the bearing. Nor do I like using the the HL CSB jig very much, but I shall persevere. I do sometimes think that the original system as described iun the CLAG site was rather easier - MJT hornblocks, Markits handrail knobs, and a ruler.....

DT


The bearings on the CLAG site are Gibson. They are not quite as consistent as the H/L ones, but the way I use(d) them, it doesn't matter.
I do agree about the bearing holes in the H/L tags, they are etched more undersize than they need be, but getting them to interference fit makes it easier to solder them straight. The Mauns help to hold them for broaching or round filing, I have tried both methods and do not like either!

As to which is easier, well...

If using the Gibson bearings, with profile milled frames particularly, my method is to set up a holder for the bearings in a pillar drill so that after setting the position they can be batch drilled for the Markits handrail knobs. It is important to cut the tails of the knobs to length before soldering them to the bearings as it is difficult to clean the ends off if they intrude into the axle space.

The horncheeks are folded up without the guide wires, which I don't use; they seem like a good idea until some solder escapes at the sides and causes stickiness. They are then inserted into the frame cutouts 'upside down' such that the ends clear the CSB wire, about 1.5mm from the top of the cutouts. Then, with the frames and the cheeks pressed flat against a piece of hardwood, large blobs of solder are placed on the outsides. The tops, now proud of the lower edges of the frames, can be removed with a piercing saw. If required, they can be cut flush with the lower edge of the frames, but I usually make just one cut through the hole and work the remains off with repeated bending.

The bearing sides are then polished with fine wet and dry and corners rounded, and they are placed in between the cheeks and the outsides squeezed with the Mauns. This does not produce a tight fit, there is enough spring back to leave them free to slide.

The thrust of the endfloat of the axles is controlled by washers of a greater diameter than the cutouts, one each side, followed as necessary by smaller ones. This way, side thrust of the axles is resisted by the frames rather than the bearings, their lateral position being maintained by the spring wires/knobs.

Now for some heresy! I prefer to have some slop fore and aft in the main bearings rather than anything other than perfect sliding fits in the crankpins. Nothing looks worse to me than wheels moving before the rods. For the same reason I only drive my model steam outline locos by the axle that was driven in the prototype. Imts...

Ted.
(A purists' purist)

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Will L
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Re: Gibson LMS 2P 4-4-0

Postby Will L » Sat Jan 01, 2022 7:12 pm

David Thorpe wrote:..You must have tougher fingers than me. The tags are made of very thin metal. As you say, to open the hole you have to hold the tag across the edges. Twirling a file? I don't have a suitably sized round file, but I do have a broach and trying to open up the hole using that is extremely uncomfortable on the fingers as the thin metal does its best to slice them open. Not moments, but several very uncomfortable minutes.

No that would hurt if you used a broach, however I use a round needle file which, turned gently will remove metal without gripping the piece, so long as you turn it anti clockwise.

Daddyman
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Re: Gibson LMS 2P 4-4-0

Postby Daddyman » Sat Jan 01, 2022 7:23 pm

Will L wrote: If you match the block to the guide, keep them paired (and always the same way up*), and then fit them to the chassis by use of a jig,any minor errors will be taken care off.


Thanks, Will. I don't do any of those things! I set up the distance between the guides using "gauges" filed from scraps of N/S, bespoke for each chassis, cut to match the holes (measured inside-to-inside and outside-to-outside) in the rods, minus the width of 2 half hornguides (i.e. one hornguide). I feel I must be doing something wrong as I find the concentricity of HL hornblocks allows me to throw them (the hornblocks) in any old way, only worrying about north-south orientation, and still get a smooth rolling chassis with 0.05mm clearance on the crankpin. But of course you've only got my word for the "smooth"...

David Thorpe

Re: Gibson LMS 2P 4-4-0

Postby David Thorpe » Sat Jan 01, 2022 7:30 pm

Thanks Ted. I must say that I have been disappointed with the HL system which, while I hope will be effective, has been rather troublesome, at least for me, from start to finish. Fortunately I found that the standard hornblocks were easier to prepare than the slimline ones, but the CSB tags were a pain (quite literally) and I found the jig so complex and awkward that I reverted to ruler and marker. As far as ease of construction is concerned I prefer the CLAG MJT/Markits/ruler method and will probably use it in future, but of course if the HL one I'm doing at the moment turns out to work very well then who knows.

DT

davebradwell
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Re: Gibson LMS 2P 4-4-0

Postby davebradwell » Sat Jan 01, 2022 7:42 pm

What a fine thing it is to start the year on a constructive discussion of practical problems in chassis building.

A few points of detail. I assume you are referring to concentricity of AXLEBOXES above. I have measured H-L in the past using a dial indicator and the hole was significantly less than a thou' off centre. However, their accuracy is unimportant as by jigging the position of the hornguides on the frames from the rods (or similar DavidA) this error is corrected PROVIDED that the orientation and position of axleboxes are marked so that it all goes back the same way round every time. These marks are an essential first stage.

Someone suggested that axleboxes can rotate in the guides and jam. Very true, but if you have this much clearance then your chances of getting the hornblocks on the frames anywhere near the correct position are very small. It all needs to have very close fits during the jigging process.

The plate that engages in the axlebox slot should be flat or it will bind. Don't forget the de-burring exercise as detailed above.

Be clear about whether it's the slot in the plate or the strip that bears on the outside that locates the axlebox - I maintain it should be the strip on the outside so the slot in the plate should be widened to be sure. Wipe sides of axlebox gently with smooth file to remove any roughness.

Here's the bottom line: it's regarded as normal to open out crankpin holes to next size to get the wheels to go round (although I think this is too loose). If we add a couple of thou' for clearance in hornguides, this means you have a total of 6 thou' or 0.15mm to distribute between all the bits as a total permitted error before it goes lumpy and preferably significantly less. This leaves yo with an odd couple of thou' here and there and it's going to take a bit of care, even more so if you want a better job. This is why I'm obsessed with the finer details.

It was going to end there as this is supposed to be helpful to David Thorpe and his trials but I'm completely behind Ted's latest comments so will add a little:

We're somehow stuck with standard axleboxes retained by the slot which I think is a lousy idea and I always use a flange on the outside of the frames, as per Ted, as there's less to go wrong although mine are by Exactoscale. Only plain hornguides are required and there's plenty of ways to produce these. It's not clear from Ted's post how he sets the hornblock spacing but I suspect he is relying on the accuracy of the milled frames - again I'm behind this approach of putting them in the right place, although there's a few potential traps here and it's not easy with an existing kit. I could never make the jigging-from-rods method work accurately and re-measuring old chassis done this way i'm as much as 5 thou' out. As for his final point - put the clearance in the hornguide - Bill Bedford put this to me once and I eventually came round to it. It's all a matter of degree, of course, but I feel it gives a chance of smoother running. You still need a working clearance on the crankpins, though, to cope with differences in crank throw and leaning crankpins/out of square holes in rods. Not sure how this bit benefits our man with his kit.

DaveB


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