Crab Comet conversion

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Le Corbusier
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Re: Crab Comet conversion

Postby Le Corbusier » Sun Dec 31, 2017 11:06 pm

20171230_161227.jpg
Tim Lee

Philip Hall
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Re: Crab Comet conversion

Postby Philip Hall » Sun Dec 31, 2017 11:42 pm

Julian,

Looks as though you are getting somewhere, pereseverance pays. May I say though, that I think your pickup wire looks very stiff from the picture, and might be restricting the free movement of the wheelsets.

I prefer a very thin wire (0.3mm hard brass) bearing on the edge of the flange, at 90° or thereabouts to it, often in the coiled arrangement we have seen on here. I have found that on wheelsets that can move up and down, such movement is restricted or even prevented by collectors that bear at 45° to the flange as you have. An alternative is for the collector to bear directly in the back of the flange, but that means periodic cleaning upside down. The flange edge idea means you can clean wheels and contact area at the same time by running the wheelsets on a solvent soaked tissue or rag placed on the track. I do use the 45° arrangement on fixed axles.

Happy New Year to all!

Philip

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Tue Jan 02, 2018 3:45 pm

Hear hear!

Many thanks again Philip. And Tim for photo magic again!

Yes pickups...however these with some subsequent adjustment are not causing problems, meanwhile I will try to learn the neater and better way of doing it.

As the motion was mostly done in September I have briefly looked at the Comet tender. This isn't a simple slot in replacement as I had thought and severe butchery of either the plastic or brass will be called for. I wonder if anyone has a picture of a converted one? My thoughts had been for a simple compensated tender but now I think a simpler approach may be to stay with the Bachmann chassis, simply stick in some replacement back wheels and somehow arrange to let the other two axles float Sharman style, hanging the front from the loco back. This will give some serious pulling power which I had not been much bothered with getting as the group layouts do not have particularly long trains..

At present the loco CofG is forward of the centre wheel so I can afford some more weight at the back from the tender, without, I surmise, (though others may be able to do better than surmise?), losing weight at the front.
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20180101_223756.jpg

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Tue Jan 02, 2018 10:16 pm

Just in case anyone was going to dig up a picture, to save them any bother I've started hacking the brass to fit the Bachmann chassis. Haven't got a full plan...probably use the usual buffer springs for the floating wheelsets. They do the job adequately on one other tender I converted.

I made two mistakes earlier. The pony wheelset is 1763-71 area. Bad, I know, but not quite as awful as I measured two days ago.

Lightly loaded floating tender wheels have derailed occasionally on my straight plank running in track. Beefing up of the springs, or other surgery, has followed. The loco is now running in impeccably and hopefully will be tested on a proper layout later this week.
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20180102_220302.jpg

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Tue Jan 09, 2018 8:53 pm

Jumping ahead a bit here is the first test on the pointwork of the group layout.
https://youtu.be/hhI32G9ckT8
https://youtu.be/5y7ACZ4HvrU
The tender has now had some I would think fairly standard butchery for those familiar with mashing up 00 gauge models. As has the Comet chassis kit, to make it fit. I imagine most people reading this would be more familiar with such tasks than I am. The main issue was to get the ride height correct. I am only having one fixed axle, the rear one. It was necessary to file notches in the plastic chassis, and the guard irons are filed nearly right through, hence a bit of wire to give strength - rather than file away part of the buffer beam.

20180105_132936.jpg
Levels as per the real thing


Even with massive amounts taken out there is only just enough width for the P4 wheels. I had to remove the plastic brakegear. The other two wheelsets will need sideplay so that will be some fun.

20180104_143417.jpg
More needed to come off still...


20180104_222543.jpg
Rear wheels in fixed bearings.


A coupling was confected from a handrail knob to give a similar coupling to a car and caravan. The idea is to give complete freedom of movement between loco and tender. But I should have thought that every mm back from the loco the weight rests increases the leverage, as the real weight bearing back of the loco is between the rear two sets of drivers at the compensation beams fulcrum, the brake rod.

20180105_132538.jpg
Towball!


The tender has been piled high with lead where coal should go. With a weight of 190g predictably the front of the loco became too light on its feet. Some weight was detachable and it now weighs 145g. The loco now weighs 333g. When I've sorted out the valve gear yet more can be squeezed behind the cylinders, just where it'll be most useful.

I've missed out quite a lot of detail which I'll get round to soonish.
Last edited by Julian Roberts on Wed Jan 10, 2018 8:12 am, edited 2 times in total.

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Le Corbusier
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Re: Crab Comet conversion

Postby Le Corbusier » Tue Jan 09, 2018 9:12 pm

Julian .... nice to see it running. Will showed me how to embed a youtube video like this ... you simply click the youtube button above and then paste in the specific code without the rest of the address - in this case ALQupJqrGJ8.

You might want to kill the volume? ;)
Last edited by grovenor-2685 on Sat Jan 13, 2018 10:47 am, edited 1 time in total.
Reason: Removed Link as Julian has deleted the video.
Tim Lee

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Tue Jan 09, 2018 9:26 pm

Great thanks Tim. Yes but how to kill the volume?!

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Tue Jan 09, 2018 9:32 pm





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Le Corbusier
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Re: Crab Comet conversion

Postby Le Corbusier » Tue Jan 09, 2018 10:37 pm

Julian Roberts wrote:Great thanks Tim. Yes but how to kill the volume?!


I think in the you tube editor you can set the volume to zero.
Tim Lee

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Wed Jan 10, 2018 7:48 am

Crab Test 1 deleted as I can't edit out irrelevant conversation! Tests 2 and 3 still there.

dal-t
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Re: Crab Comet conversion

Postby dal-t » Wed Jan 10, 2018 11:40 am

I really wish people would post large warning notices on videos like that for those of us with extreme vertigo - tummy butterflies just subsiding after three or four minutes! Useful reminder, though, to stick a suitable attention-grabbing notice on the board for my new test track - FIT BUFFER STOPS BEFORE ANYTHING ELSE!
David L-T

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Wed Jan 10, 2018 1:58 pm

Apologies for inducing vertigo or any other illness or annoyance. Only one board of the layout was conveniently available. The point was, to test it over some pointwork. Having folded the tender guard irons to clear the rails running was perfect in each direction.

As this is my first 2-6-0 my interest is primarily in how the loco runs and behaves, though I will write up the rest of the assembly as it happens. Ideally now is the time to explore the issues thoroughly, before the valve gear is on and paint job complete. I think I've understood and solved to my satisfaction the issues of 4-4-0s and 0-4-4s, and locos without carrying wheels, but the issues around a 2-6-0 are less straightforward than I had expected and I want to be sure it runs as perfectly as my previous efforts.

A trip to a layout under construction on Saturday showed up potential faults. There was a board break followed by a curve. A minute downwards change in gradient coincided, as the boards had not been painstakingly levelled to an identical horizontal, this being an informal get together. As I expected, the loco ran onto the curve fine when running solo, but with the heavy 190g tender the front end derailed. The pony stayed on the rails but the front driving wheelset did not, failing to take the curve. So this is the issue I will be looking out for.

Yesterday I increased the weight by about 20g finding a little room for lead near the front driving wheels in the loco body. I then found for the first time a problem going backwards with the loco running solo, the rear wheels derailing. Again, quite predictable. However with the 140g tender (without its detachable weight) order was completely restored, and the ensemble seemed together to be perfectly balanced as per the videos from yesterday evening.

The balance of pony and front drivers is more delicate than I had surmised for getting them to stay on the rails. I had discovered this on 31st Dec. I think that a compensation arrangement between the two would be ideal as, as has been shown, the force exerted by a spring varies so much with the up and down movement, while what is needed is a consistent weight relationship whatever the up and down situation. However that would be impractical in this situation unless thought out from the start. So on this model it will be a case of adjusting the spring force of the front drivers if that is possible while maintaining sufficient weight on the pony, should any further problems arise.

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Sat Jan 13, 2018 9:16 am

20180112_074953.jpg


From here it's mostly final details...but I've very late in the day seen an obvious problem. The loco body is not firmly made! The footplate (or running board?- not quite sure of
correct term) isn't firmly attached at the front below the smokebox saddle. I don't know if it has come loose during the proceedings or was always like this. Explains why I had problem getting chassis really level even before wheels went on, and why I am not getting a good vertical from the front view. The cab is vertical. It's nearly acceptable - I find getting no twist from front to back at all is very difficult - but the amount here is something I'd like to improve.

What alerted me to this was trying to get the loco and tender footsteps lining up on both sides . (The steps are the only things that are level in this funny hybrid mismatch.)

I will report on remedial action. Prior to this a morning spent reassessing the fit of the motion assemblies into the chassis now that the latter seemed to fit the body well and no distortion was occurring when screwed together. The trio of motion assemblies seemed to disturb that fit so they were separated and reattached to each other rechecking at each stage the fit in the body.

20180112_075042.jpg


The valve gear assemblies look like this. The slide bars are very vulnerable as is the motion bracket until all the separate motion assemblies are soldered together to the cylinder assembly. How robust they will then be remains to be seen. The process of attaching the gear will be like a Catch 22 rubik cube. The crosshead can't be slid into the slide bars if all the gear is riveted on prior to insertion as per instructions. And so on...a very calm mentality is going to be needed!

One thing is clear. The clearance of the motion bracket to front coupling rod is limited and that has more bearing on the sideplay and minimum radius than I thought of right back at the beginning. It's a bit difficult to pick out the bracket in the picture from all the other gubbins.

20180112_080016.jpg


Meanwhile here is a pic showing the front pickup and brakes arrangement. The side on view is not showing them to be super subtle but with all the waggly bits they won't be so obvious. Apologies to Philip that my unsubtle pickups still are in place. Till I learn the better technique these do the job and when blackened won't be very obvious.

20180111_174458.jpg

Philip Hall
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Re: Crab Comet conversion

Postby Philip Hall » Sat Jan 13, 2018 11:52 am

Julian, No apologies needed about the pickups. They’re not obvious from the side view and from your video they seem to work fine. So job done.

Re the distorted body of the engine: I have found this on many RTR models and usually a gentle twist, or sometimes something more brutal, straightens things. A lot of them these days have the main body assembled from several large components, often glued together with some kind of superglue that is difficult to shift. If they have been put together slightly askew, patience and much heaving is required. As an aside, I wish we could find out what kind of superglue Hornby and Bachmann use as it’s much stronger than the stuff we can buy!

Philip

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Sat Jan 13, 2018 3:00 pm

Yes Philip I'll glue this up with Araldite - the proper 24hr stuff!
Attached are pictures showing how much I can move the smokebox saddle. Also ones I meant to attach to show the front pickups
Attachments
20180102_125153.jpg
20180102_104349.jpg
20180112_075205.jpg
20180112_080340.jpg
20180112_080415.jpg

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Mon Jan 15, 2018 8:07 am

A proper test was done yesterday on the layout Kettlewell, which belongs to one of our WS4G members and was being exhibited at Johnstone near Glasgow.

The loco and tender unit was run through the entire layout at full speed put both ways round on the track. No single derailment. I was unable to test it through the place that frequently gives most trouble, the join from fiddle yard to layout, that will have to await another time. But I am reasonably confident that the suspension is working as I intend. The group layout Calderside has more challenging problematic areas but can only be erected in its entirety for shows or on special occasions. I have found however that my ridiculously short test track shows up when there is a problem and when there is not.

So here are a couple of videos. Why do I put this here? Because if a picture says a 1000 words, a video does all the more. You can see what I mean when I say the layout has complex trackwork, and what I mean by full speed, in the first video. The second shows a bit of slow running. And just in case anyone needs reminding this is my 8th loco in P4





Revisiting the issue of the sideways tipping gait of the loco front view, I have realised the problem is one that I thought I'd solved earlier, that I need to adjust one of the beams. Putting a piece of folded paper between beam and axle on the RHS made it stand correctly and was possible without disassembly. So it's quite easy to do the same with a piece of brass but to make it fixed adequately the rods will have to come off and wheel come out. Not a big deal with this fairly easily disassembled loco. (It took a lot more time to make it so but now pays dividends.) I probably won't glue the loco body as discussed on Saturday with Philip simply on the grounds of "if it ain't broke don't fix it" - plainly the glue is broke but it doesn't seem to matter!

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Le Corbusier
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Re: Crab Comet conversion

Postby Le Corbusier » Mon Jan 15, 2018 8:18 am

Julian,

I like the videos. As well as helping in following the particular thread, It also gives me a good idea of locos and stock running through P4 trackwork. A good way to set benchmarks for both .... and helpful with problem solving. All very helpful. :thumb

I spent considerable time on Sunday watching Sandford and Banwell this weekend which ran very smoothly.
Tim Lee

Julian Roberts
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Re: Crab Comet conversion

Postby Julian Roberts » Mon Jan 15, 2018 8:46 am

Cheers Tim. I made the comment about videos in regard to comments made on another thread yesterday that I haven't got time to reply to....!

Philip Hall
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Re: Crab Comet conversion

Postby Philip Hall » Mon Jan 15, 2018 10:19 am

Julian,

These bodies can be very ‘bendy’ and require a lot of heaving to get them square if they are out of true. Heaving to the point of hearing ominous cracks when you do it! Once I’ve got there, usually they stay put but just as insurance, when assembled, I drop some superglue or plastic solvent into some joints, making sure none gets between the body and chassis.

You say this is your eighth locomotive in P4. I rather think this suggests that you know what you are doing, and the video proves the point...

Philip


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