Tim V's workbench - broad gauge tomfoolery

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Russ Elliott
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Re: Tim V builds a chassis

Postby Russ Elliott » Sat Jul 31, 2010 12:26 pm

Looks like you've pinned those wheels to the axles, Tim.

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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Sat Jul 31, 2010 1:10 pm

Not yet. As part of preparing the axles, I drill them for pins - so that I am drilling through the axle into the soft plastic, not from the plastic into steel, which will cause the drill to wander.
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martin goodall
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Re: Tim V builds a chassis

Postby martin goodall » Sat Jul 31, 2010 3:53 pm

I have been following this thread with great interest. I see that the holes for the pins have been drilled from the outer face of the axle at an angle so as to take the hole out through the plastic of the wheel hub. I can undertsand your reason for doing it this way, as you have explained in reply to Russ.

Two questions. First, when drilling at an angle into the end of the axle, how do you start the hole so as to prevent the drill from skating across the face of the axle - do you use the dimple already present in the end of the wheel? (It is just that drilling into the axle at an angle like this strikes me as being a bit tricky.) Secondly, I wondered why you had drilled the holes at this stage, bearing in mind that you will not yet be inserting wires and fixing them with super-glue until you are absolutely sure you won't need to get the wheels off again for any reason.

I certainly don't question the practice of pinning through the wheels to fix them to the axles. It was recommended by Guy Willimas, and my own experience has confirmed that you cannot rely on Loctite alone to fix the wheels on the axles.

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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Sat Jul 31, 2010 4:59 pm

In this thread I have tried to steer away from expensive jigs and tools, and tried to show that with minimal equipment, it is possible to easily build a P4 steam loco chassis.

Now you've asked the question, I'll have to take this project to a different level, but only to reply to this question! It is possible to build locos without pinning the axles, but over the years I've gradually pinned all wheels.

How I do it is to make the axles over long as in this rough sketch
Axle sketch.jpg

held in a vice at approximately the angle shown, filed horizontal on the end, drilled through with a vertical drill, then the end is machined back to form the face.

The axles are drilled as part of making the axles, but at this stage of construction I have not drilled the wheels yet. As things stand I'm not anticipating removing the wheels from the axles again, the engine runs smoothly, so why should I? It only leads to problems. I expect to build locos without extensive fiddling. For example, any spacing washers can be clipped on and off easily. The construction means that the axles can be dropped out of the chassis easily, which I will have to do shortly for painting.
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Philip Hall
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Re: Tim V builds a chassis

Postby Philip Hall » Sat Jul 31, 2010 5:36 pm

I usually do it the way Martin surmised, just by drilling through the dimple on the supplied axles at an angle with the electric drill. If there isn't a dimple, I just make one in the end, gently, and gradually rotate the drill around until I've got the approximate angle. Of course, Tim's way is a lot more elegant! Sometimes with Gibson wheels you have to make new axles anyway, because they might be too short, so then I think I'll try Tim's method next time.

It's important that you drill the axles first, so that the final thing you do once all is running OK is to put a drill through into the plastic centre and put a pin in. Drilling with the wheel on could lead to the quartering moving while you're doing it.

Philip

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Re: Tim V builds a chassis

Postby martin goodall » Sat Jul 31, 2010 8:43 pm

Thanks to both Tim and Philip for these replies. Now, just to throw another pebble into the pond, but still on this point about pinning the wheels to the axles, would anyone like to comment on what Chris Pendlenton said about this on page 210 of MRJ 200? I just happened to read it again a few moments ago, and wondered what others might think.

[Sorry, Tim. I don't want to complicate what was intended to be a simple and straighforward account of your chassis project - I think you have done everyone a huge service by presenting this very well illustrated step-by-step account. But, as Russ noted, you did (or will) pin the wheels to the axles, so it is a relevant query which arises from this thread.]

As I explained in a different thread some months ago, I hit a major snag when trying to do a quick 'drop in' conversion of a Bachmann 45XX, so I may well go down the Comet chassis route. The use of split axles / split chassis for current collection is a very interesting aspect of this project. I have fought shy of split axles before, but this account may well encourage me (and perhaps others) to give it a try.

I look forward to reading futher episodes in Tim's chassis project - it is certainly shaping up very nicely.

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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Wed Aug 04, 2010 4:24 pm

Unfortunately, my MRJ supplier has let me down, so unable to comment myself!

Meanwhile, I've prepared the chassis for painting, by soldering the DCC socket in place and putting the brake hanger pivots onto the chassis. In line with normal practice, I've made the brakes so they can be removed, by soldering on a short length of wire with a tube as shown here. The brakes will just clip on and off these pivots.
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Courtesy of Dave Holt, the trucks have their axles sprung - set out on the CLAG site http://www.clag.org.uk/comet-pony.html . The trucks will bear against rubbing plates to support loco weight. The chassis has had all its extra holes drilled for holding screws, and has been sprayed with Halfords matt black.
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Philip Hall
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Re: Tim V builds a chassis

Postby Philip Hall » Sat Aug 07, 2010 3:23 pm

To answer Martin's query, I've pinned quite a few wheels over the years and not had a problem with the quartering still slipping. I must admit, though, that I've never tried a bit of force, so maybe this isn't as secure a method as we'd all like to think. I think it's very important to pre-drill the axles as Tim has described, and to take great care after you're certain all is well to drill gently into the plastic so as not to move anything. Guy Williams used to drill from the wheel into the axles so he must have had confidence the drill wouldn't wander as it hit the steel or was just lucky or brave. I agree that a proper bushed wheel and a firm press fit is very sound engineering, but not all of us are blessed with Chris's skills in achieving this. He's also got a point when he says that the engines many of us produce do not require to be thrashed on a big circuit for mile after scale mile.

Ultrascale wheels are a very good fit on the axles, and as Chris says, any Loctite will be squeezed out as the axle goes in. Sharmans, being made of a more bendy plastic, used to 'shrink' around the axle after they'd been on a while, and I think Gibsons might have similar properties. I don't always pin, only when I think it might be needed. I always pin outside cranks, for example. With Ultrascales I drill the axle at the outset, then only right at the end of testing do I drill into the wheel.

Philip

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Re: Tim V builds a chassis

Postby Horsetan » Mon Aug 09, 2010 11:03 am

I never pin driving wheels. Having spent all that money on them, I just wouldn't like something to go wrong whilst I'm drilling them. It's Loctite 601 for me.
That would be an ecumenical matter.

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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Mon Aug 09, 2010 6:33 pm

I used to glue, but having had wheels slip over the years, just slightly, but enough to put the quartering out, I've adopted pinning, successfully. It does not wreck the wheels, I've even successfully pushed the pin out on one pair in the past to change an axle.
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Re: Tim V builds a chassis

Postby Tim V » Mon Aug 09, 2010 8:32 pm

I've reassembled the chassis, and I'm trying the pony trucks in place, working out how much depth I need for the rubbing plates.
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Trucks are only temporarily in place. The rubbing plates will be between the top of the truck and the frames, carrying some of the body weight.
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Re: Tim V builds a chassis

Postby Tim V » Tue Aug 10, 2010 8:22 pm

I've put the rubbing plates onto the chassis, and started on the cylinders.
Using a piece of 1/4" brass rod, a mouse mat and pressure from my hands, I've put the bend into the cylinder wrappers. I could have annealed them, but they are then easily dentable.
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I've bent up the slide bars. I've also soldered a piece of single sided copperclad (as opposed to the double sided I usually use for chassis spacers) across the width of the cylinders, before cutting through to insulate each side. Note that the gap is off centre, so I can drill through for the holding screw without bridging the insulation :!:
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Here I'm soldering the slidebars together, using a wooden clothes peg (very useful, always have some handy).
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I'm using an Antex TCS 50W temperature controlled iron for all this work, set at 370°. ALL soldering work is done on a different bench - keeping flux etc away from my steel tools.
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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Mon Aug 16, 2010 3:35 pm

So I've looked at this, Roche says 5.2mm, Bachmann says 5.1mm, Malcolm Mitchell (as Churchward) says 4.5mm and Comet says 3.7mm. I don't have a handy real 45xx to look at closely. I could scratchbuild a new crosshead, slidebars and motion support bracket, but that would not be in the spirit of this project. Utilising the Bachmann cylinders would be an idea, but I don't have one, as I bought the body only, as a spare. I presume that as you say Philip, Comet have utilised their standard lost wax crosshead to reduce costs. At the price we pay, I don't think we can object.

My main concern is that the cylinders and slidebars go together squarely, and remain in alignment. I am reluctant to start building slidebars from filed rail, a scratchbuilt crosshead is not difficult, but what puts me off is extra time it would take building it.

I don't look at my models from very close up, so I've decided to use them "as is".

Philip Hall wrote:Tim,

Looks to be a nice way to start an engine. However, from looking at Comet's own photo of the result in the magazines, it seems they've used their standard crosshead. This to me is too small, making the slidebars too close together. I first noticed this in Tim Shackleton's book when he built a 'County' using Comet bits for the valve gear. Maybe you could investigate whether the crossheads and cylinders can be re - used from the Bachmann chassis, with slidebars replaced and beefed up. I have one of these to go into shops one fine day - I find myself unable to resist just a few GW engines for the new layout.

Philip
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Re: Tim V builds a chassis

Postby Tim V » Mon Aug 16, 2010 3:47 pm

By using a selection of blocks, pieces of paper, card and a piece of steel, I've spaced the bars apart ready for soldering, and clamped them using a parallel clamp. Everything has been carefully checked for squareness. I'll try to use a higher melting point solder for the bars to cylinder joint, as there is subsequent work to be done.
IMG_3439.JPG
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Philip Hall
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Re: Tim V builds a chassis

Postby Philip Hall » Mon Aug 16, 2010 5:54 pm

So I've looked at this, Roche says 5.2mm, Bachmann says 5.1mm, Malcolm Mitchell (as Churchward) says 4.5mm and Comet says 3.7mm.


Nice of you to look it all up Tim, and to have my suspicions confirmed. But, as you say, the use of standard components is reasonable enough. I'm lucky, I do have a complete loco so if I do decide to ditch the Bachmann chassis I have another option.

Philip

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Russ Elliott
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Re: Tim V builds a chassis

Postby Russ Elliott » Mon Aug 16, 2010 7:25 pm

Tim V wrote:So I've looked at this, Roche says 5.2mm, Bachmann says 5.1mm, Malcolm Mitchell (as Churchward) says 4.5mm and Comet says 3.7mm.

Tim - are these distances between slidebars?

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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Mon Aug 16, 2010 8:15 pm

Yes, as suggested by Philip.
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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Mon Aug 16, 2010 9:19 pm

Well I've gone ahead with the cylinders as supplied.
The motion bracket between a peg
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Soldered up, waiting to be cleaned
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Oh dear, just look at the difference in size between the gap in the motion bracket and those slidebars, I should have listened to Philip :!:
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I'm going to think about how to deal with this, the first major setback on this chassis.

Any ideas chaps?
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Russ Elliott
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Re: Tim V builds a chassis

Postby Russ Elliott » Tue Aug 17, 2010 10:32 am

Tim V wrote:Any ideas chaps?

Doesn't look pretty, does it? I'm not sure which of the motion bracket or the bar spacing is wrong, but maybe the kludge would be to pad the bars in the motion bracket area, but then that might end up with a gap at the top of the motion bracket between it and the body. Does Comet have a view?

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Re: Tim V builds a chassis

Postby steamraiser » Tue Aug 17, 2010 5:46 pm

J.H.Russel's drawing indicates 4.5mm.

Anyone got easey access to a full size loco?

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martin goodall
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Re: Tim V builds a chassis

Postby martin goodall » Tue Aug 17, 2010 8:00 pm

"Any ideas chaps?"

I fear the only really satisfactory solution is going to be to scrap the slidebars and substitute new slidebars (and crossheads) from a different source. Fortunately, these fittings are available as etchings or castings from several suppliers. I imagine that Tim (like most Great Western modellers) may well have one or two examples already stached away in his stores.

I appreciate that Tim wanted to build the Comet chassis 'out of the packet' as a demonstration of the comparative simplicity of this approach. However, there are times when substituting components from elsewhere is unavoidable. This seems to be one of those occasions. It will be quicker in the long run than soldiering on with components which are clearly not of the right size and shape.

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Re: Tim V builds a chassis

Postby Philip Hall » Tue Aug 17, 2010 10:12 pm

I think Westward did some crossheads which I thought I had but can't find now. Also there's some very nice machined nickel silver ones from Markits. But I don't have dimensions for these two, so no idea if they're any better than the Comet ones. Maybe David Geen can help with some etchings from the 45XX? Either way, I think I'd modify the slidebars rather than scrap them, once you've got new crossheads. Seems like Comet got some of the dimensions right after all.

Philip

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Re: Tim V builds a chassis

Postby Tim Hale » Wed Aug 18, 2010 1:21 pm

Also there's some very nice machined nickel silver ones from Markits. But I don't have dimensions for these two, so no idea if they're any better than the Comet ones.
I think that I first suggested this source on June 20th but Mr. Venton was committed to using the items supplied with the kit- good luck to him.

Tim Hale

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Tim V
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Re: Tim V builds a chassis

Postby Tim V » Wed Aug 18, 2010 5:25 pm

Thanks guys, but I did say that I'm trying to show that it is possible to build a competent chassis, without recourse to outside bits and pieces, or a fully equipped workshop. If this model were to be the "bees knees" I probably wouldn't start with the same basic products. Also I'm thinking that this thread is becoming a review of the Comet kit, rather than "I'm building a 45xx, lets see what we can throw away".

Perhaps I could also put these comments to Comet, but I know what they would probably say - that the crosshead is their standard one, and to make loads of different ones would become economically non-viable. They used to provide etched crossheads in their earlier kits, which unless you had the Guy Williams articles in the MRC (or his Model Locomotive Building in 4mm scale the Ian Allan version which I think is still useful), were very difficult to build.

I think also this is getting away from the basic rightness of the kit after all, I have got a running six-coupled chassis, without a great deal of work. If this was a six-coupled tank with no outside cylinders, the thread could stop now other than the fine tuning.
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Re: Tim V builds a chassis

Postby Tim V » Wed Aug 18, 2010 6:09 pm

This is how I modified the motion brackets.
I've bent up a single piece of etch off cut, to reduce the size of the gap. Why have I done this? There is only one piece, instead of three, a lot easier to solder. It won't fall apart :!: I've used my temperature controlled soldering iron set on high, and high melting point solder.
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And here is the result, ready for cleaning up.
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