Re: Tim V's workbench - latest shenanigans

[Tim V]

I have assembled the motion bracket onto the slidebars, and included an extra piece of scrap to stiffen up the assembly. Here I'm using toothpaste to bed in the crossheads.

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Once they are running smoothly, I'll tackle the piston rods.

[Captain Kernow]

Here I'm using toothpaste to bed in the crossheads

Your teeth won't stay white very long if you re-cycle that lot!

[Tim V]

Having used toothpaste, I remembered I normally use Brasso.......

[Mike Garwood]

Tim
Was there a lot of 'fettling' to get the crossheads into the slide bars? I usually have to file a fair bit out of the crossheads to get a good running fit. Just curious to see if there had been an upgrade in the lost wax brass casting...

cheers

Mike

[Tim V]

Not really, the trick is to remove the minimum you can get away with, it has to be free, but not sloppy.

I have built up cylinder side, having managed to solder up the small end solid I made a better effort by soaking the Rizla paper in oil second time.

When I want to have a moving joint I use a Rizla paper (as in the roll up cigarettes) between the components. It usually works OK, it just didn't tonight

[Russ Elliott]

Rizla Red and Rizla Green: 0.03mm thick.
Rizla Blue: 0.025mm thick.

[Tim V]

I use the green, but I've never put the vernier on them.......

[Mike Garwood]

I always use the green, they are a better smoke...

[Mark Tatlow]

When I want to have a moving joint I use a Rizla paper (as in the roll up cigarettes) between the components. It usually works OK, it just didn't tonight

Add a tad of watch oil to the Rizla just before soldering. Give it time to perculate through the paper and around the bearing surface but not any longer so that it does not get to the point you want to solder.

[zebedeesknees]

Chemically blacken the bits that you don't want the solder to stick to. It won't!

Or before you start, chemically blacken the whole lot, and just clean off the bits you do want the solder to stick to...

[steve howe]

Tim,

Can you tell me where you got the body shell? I have tried to get Bachmann bodies as spares and was told it was not possible.

Really useful thread by the way.

Steve

[Tim V]

I bought the Bachman body at the Stafford show, I think the stand was close to my layout so looking at the floor plan it looks like "Richard Spares" 01443 685163, but I can't guarantee that.

I like to make the big end nearer the scale width (6"), so here I'm increasing the size. The scrap is cut into two, then put either side of the connecting rod, the holes lined up with cocktail sticks before soldering together.

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And the result after filing looks like this.

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[Tim V]

I have arranged with Gordon Ashton to place the chassis on his "Beginners guide to P4 modelling" demonstration at Scaleforum.

Any questions, he should be able to answer, or I will be on Rolvenden.

[Tim V]

The trucks have been worked on, following Dave Holt's ideas on suspension. I have used a pin to hold the axle in place.

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The sideplay is controlled by washers, which are usually on the etch (as shown on this much older truck etch), but this kit only includes two washers. I shall have to look elsewhere for more washers.

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[Tim V]

A photo opportunity on another chassis I'm working on cropped up.

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Shows how beautifully simple these Comet chassis are. Note that I've put an extra piece over the top to strengthen the weak are around the cut-out.

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You can just see where I've bent the retainer to hold the block in place.

[Mike Garwood]

Tim

Saw the chassis at Scale4 this weekend...nice work! Impressed with the rubbing plates. Just one question, what swg of phos bronze wire did you use? Good to see you being kept occupied, hope the beer did'nt run out on Saturday evening!

cheers

Mike

[Tim V]

I used too thick a wire, should have used a thinner one!

Last night was a better pub with beer and a curry house next door.....

[Steve Taylor]

Tim,
I'm reading all this with some interest, being shortly to undertake a v2 build during an "enforced medical holiday". In the meantime I'm playing around with a couple of J-72s including a comet version using the sprung hornblock system you've shown. Looking back at what I've done so far I like the method you've chosen to hold the "springs" that restrain the hornblocks downward travel. What size are the screws you've chosen and since the detail is unclear am I right in assuming they are countersunk?
Cheers
Steve

[Tim V]

Holes drilled 0.6mm, then tapped 16BA (carefully!). 16BA studs put in (which are just short lengths of 16BA screws) and soldered on the outside, then filed down.

[Tim V]

I gave Geoff Brewin a copy of this thread, and this was his reply.

Hello Tim,

Nice to see you at S4um, and thanks for the CD.

I'm glad you seem to have enjoyed building the 45xx chassis which, as I explained, I did for my own benefit and releasing to the wider public was a bit of an afterthought. I wanted a couple of 45xxs for my own layout and had acquired the Bachmann bodies, and so decided to etch some frames that would use Comet's own standard cylinder and pony truck components. The difficulty was that I soon found that I couldn't use the our standard bar frame pony truck, as I needed pivot points closer to the bogie axle than they allowed, and I couldn't use our standard GWR 2 cylinder set, as the 45xx cylinders were significantly shorter. We toyed with the idea of getting new masters made for the cylinder wrappers so we could get them cast in whitemetal as is the case on all other Comet chassis, but discarded that on cost grounds (don't forget, this was only meant to be a little private project) and so I included the half etched cylinder wrappers. My own experience with that method on other manufacturer's kits is that if the cylinder wrapper is only just wide enough then any slight misalignment at the start of the forming and soldering process means that the wrapper doesn't cover the cylinder endplates by the end of the process. To cater for my own inadequancies I therefore made the wrappers slightly too wide so that a small amount of excess will need filing off once the cylinder set has been assembled. By this time I was aware that I was spending too much time on this little project that was only meant to be a pair of mainframes, and so I etched what I had drawn up to then. Having assembled my own first sample I made some small adjustments to the drawings and then re-etched it. Finding that it fitted the body and fitted my purpose a decision was then made to release it as a Comet chassis, prompted coincidentally by a few enquiries at exhibitions on the lines of, "Why don't you do a small prairie chassis to go with your big prairie chassis?'.

So there you have it. The story of how the Comet 45xx chassis came about. Not a decision taken after many hours deliberation and research, but something that was done to meet one of my own needs, and if it helps other modellers who want a 'beautifully simple' chassis then we're pleased to be able to help.

Regards,

Geoff Brewin

Comet Models

[Tim V]

Martin Goodall said
"The last post on the 45XX chassis of which I was aware was on 19/9 showing another Comet chassis (followed by some comments concluding with Geoff Brewin's note of 30/9). Having found this thread extremely interesting and useful, I was looking forward to one or more further episodes leading to illustration of the fully completed chassis, together with any observations on testing and adjustments when tried on the layout. [Some people are never satisfied!]"

Currently the project is on hold as I want to put the chassis under a different Bachman body.

However, it has been tried on Clutton and works very well without adjustment - that is why I like these new Comet chassis, they work straight away. Once the new body arrives, I will be working on the brake gear and weighting etc to finish off.

[Tim V]

Work is proceeding on making new pinned axles for the Bachman 45XX, and I'm also while the jigs are out making axles for a Hornby Grange conversion.
A very simple jig for mounting the new axle in to hold it ready for filing.

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A quick file across the axle end using a file dedicated to steel. Steel blunts files, so keep separate brass/steel files.

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I've drilled the hole using a 0.55mm drill, with a spot of oil for lubrication.

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[Tim V]

To the lathe.

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Axle faced off.

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Using a vernier and a parting tool to set the length of the axle. The collet is turned by hand carefully to set a mark for the length.

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Cleaning out the hole with a broach, to remove swarf

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Using a George Watts puller to get the gear wheel off.

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Using a George Watts wheel quartering jig to set the wheels.

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[HowardGWR]

How do you cut off your copper coated spacers Tim so that you don't lose some of the edge that you need to solder them to the frames? I found it a bit dodgy when I cut mine.

[Tim V]

I actually use the milling attachment on the Unimat, but for those without machine tools, I would use a hack saw to get them near to size and then file down.

I saw a tip down at the EM Skills Day, where John James was using brass angle around the copper clad, it didn't have to be so accurately made using that method.