andypugh

Yes, plywood is the plan now. At home I am much better set up for metalwork and machining than woodwork, though. All the woodworking stuff (with which we are rather well equipped) is at my parents' 250 miles away. Woodworking in my machine-tool shop always makes a nasty mess.

No I am not, my mill is too small and the blocks of PU are too small.

If the core box and pattern share a split line, is there any reason that the pattern can't be the core box too? I am probably going to CNC mill the patterns from high density PU model board. I found it in a skip, but knowing that it is expensive I would prefer to economise.

I think it depends in the silver solder. (And, to an extend, on the country you are in) There are soft-solders that contain silver, and those rather confuse matters. And some brazing alloys contain solder. To an extent the difference between brazing and silver-soldering is as much about the technique as the filler material. If you apply the rod in a fillet then it is brazing, if you allow the filler to run into the joint by capillary action then it is either brazing or silver soldering, depending on your point of view.

It occurred to me on the way in to work today that you can ram up the core through the core print holes. You are right, I was imagining that the mould would be rammed up with the pattern sat on the front face with the holes. But of course it will be sat on the split face at that point.

12" x 304.8mm x 8"

A further thought: If you made a sand mould with a plain pattern you could impress the texture in the sand, as at that point the background is the high spots.

Nothing to do with old vehicles, but I don't know of anywhere else that amateur pattern-makers hang out. I want to have this cast: I have been quoted £130 for laser-cut parts to be fabricated or £80 for a casting, and as a casting will be a better solution too, that is the way I want to go. It clearly needs a core, and I am planning to make it a single-part core. I imagine that the foundry can ram up the assembled core-box from the far (closed) side of the part and then form a radius on the core at the ramming-end by hand? I think I need to split the main pattern at the indicated plane to be able to extract the core-prints for the top holes. I am wondering if it would be reasonable to _not_ have core prints on the two large front holes. This would make ramming up the small front section of the pattern easier. This would mean that the front "holes" of the core rest against a flat surface. Is this OK? I can live with a fair bit of flash on the holes, the part is to be machined square on all sides. Will a big left-side core print and two smaller top ones be enough to support a core? I imagine that the core face that rests against the flat face of the mould would be at the top as cores float in iron?

The track-rod ends might well have been bought-in parts. There is quite a lot of work in them, but not really much more than necessary to make a component with the required function. Nowadays they use ball-joints in that application, but there isn't that much less work in those.

That doesn't help very much with getting a neat logo and lettering. Thinking about this some more, with a DLP printer you could actually print the base, glue on some metal mesh (or hessian, or wallpaper) then carry on printing the lettering and logo on top. However, that probably isn't something that you would get done by a commercial 3D printer. As for cost, this company charge 20p per cm3 + £4 per part, so a chassis plaque pattern would be in the region of £25 http://www.3dprint-uk.co.uk/portfolio/pricing/ (though I think that other higher-resolution processes might be more suitable)

If you are not set on using period technology then I think that 3D printing could be useful here. Actually doing the texture is a bit tricky (computationally expensive) but I can imagine 3D-printing the lettering with a support structure then pressing that into a wax texture. Of course, you would need a 3D CAD model of the plate, something a little bit like this:

That comes out at less than 1 thou? That can't be right.

If it was me, I would arbitrarily decide 25 thou. :-) My interpretation of https://www.hastingsmfg.com/ServiceTips/ring_gaps.htm is that 22 thou is fine. In fact it seems to say that you could start at .020 and allow a further .009 as wear limit.

Joking aside, there are two ways to argue this, and it depends how much you value actual original parts over good replacements. Ben seems to be buying Dennis chassis in bulk, and I suspect that this is just an original Grover washer harvesting excercise.

It isn't load-bearing and will never be > 100C, so why not bodge it up with epoxy putty / Loctite / Edam?

It is so long since I did a long bend that I can't remember. And when I did I wasn't all that bothered as the next stage was to hammer the flanges flat onto the polypropylene side armour.

To answer a question not asked... I have one of these and it is rather useful for this sort of thing. I used it to make the silencer and fuel tank for my Ner-a-Car. http://www.axminster.co.uk/750mm-sheet-metal-worker The bending and rolling capacity is rather more than the cutting capacity. And I think it was a fair bit cheaper when I bought mine. Curiously there are several on eBay at much higher prices than the Axminster one.

http://www.arceurotrade.co.uk/Catalogue/Measurement/Centre-Finders (especially handy for picking up a centre-punch mark)

Larger Motor House required, that one seems to be nearly full!

Machining the angled underside of the heads might solve both problems.

You can get away with a bigger dedendum, and a smaller addendum just means a smaller blank, so you can use a normal cutter to make a mating gear. It will just have more root clearance than needed.

This thread is so far off-track that it will never find its way back, so just one final link to a poem I heard parts of as a child. http://www.bartleby.com/380/poem/222.html

To stray off the subject of vehicles completely, I suspect that Megatherium might have been in general use for "Huge" at the time. According to the Wikipedia article it was the largest animal known to have lived until the discovery of the dinosaurs. This Google Ngram shows the history of the popularity of the word. https://books.google.com/ngrams/graph?content=megatherium&year_start=1780&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cmegatherium%3B%2Cc0 The Crimean war was 1853-56. Megatherium was discovered in 1788, and at the time of the Crimean war the only dinosaurs known (again, according to Wikipedia) were relatively small. Well, if you can call an Iguanodon small... "Jumbo" appeared in London some time around 1880, s that word wasn't available. They might have called it the "Mammoth War Horse" (I think that mammoth had been known about since antiquity) but perhaps that didn't have the same ring. Hyracotherium was relatively tiny, and (as far as I can see) wasn't linked to the horses until the discovery of Eohippus in 1876.

What is the tooth count of the mating gear? It is quite common to shift the profile of gear teeth pairs with low tooth-count pinions to avoid undercutting the smaller gear. This is an offset of the pitch circles of the two gears by equal and opposite amounts. Alternatively they might be using nominal pitch-curdles but unconventional addendum and dedendum proportions.

Looking on the Internet the Rotaped system is rather more modern (1941) and seems to be somewhere between a Caterpillar Track and a Dreadnaught Wheel