andypugh

Would it not be easier to build the pattern up from bits of MDF / plywood / low density UPVC since it is mostly flat surfaces that will have to be at slight angles to provide draw.

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.

I am probably going to CNC mill the patterns from high density PU model board.

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.

Is there any data which shows the comparative strengths between a silver soldered joint and a true brazed joint?

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.

The core sand (probably bound with a CO2 setting resin) would be put in and rammed up via the outside faces of a couple of the core prints

It occurred to me on the way in to work today that you can ram up the core through the core print holes.

However I don't see that it would be significantly easier to not extend the core prints of the big front RH face (top when casting) and it will involve more work to remove the flash from the 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.

What are the approximate dimensions of this box?

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?

what gets me is the amount of intricate work involved to manufacture these machines.

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.

or he could just do what i`v said at #47:

http://www.anaglypta.co.uk/our-papers/brand/original

rather than go down expensive and time consuming guff...

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)

We don't have this plate for ours and are going to have to make one. Can anyone tell me how they produce the background texture on a casting like this? Is it a sheet of material cut around the letters or maybe with letters stuck on with a thick glue? I really don't know but a lot of old plates have this style.

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:

I've been told one old simple calculation for the ring gaps - cylinder diameter/3000.

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

The engine bore is 75mm and this piston ring end gap is 0.022". From the limited information I have managed to find it would seem like they would originally have been set at around 0.012" but what would be a sensible limit before replacement?

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.

If you are seeking genuine grover washers I don't think 'bodging' is on the menu, be it edam or not. New casting please.

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.

I blasted the water jacket tops from the engine. This revealed that one of them has a crack running alongside the old braze repair. I might have a go at another braze repair but it is probably time for a new casting;

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

do you find yourself going to 90* for the centre of any sheet being worked...then bringing back the ends to 90*

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.

Did you roll the silencer tube yourself? How is the seam joined?

 

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.

With the flange in the vice I used a dial test indicator to find the middle.

http://www.arceurotrade.co.uk/Catalogue/Measurement/Centre-Finders

(especially handy for picking up a centre-punch mark)

Larger drip tray required.

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

The heads on these stock ones seem to be too big – these are the only ones that we have at present and they are not long enough – should be 2” and these are 1 1/2"

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

Another challenge to overcome as that means a standard cutter or hob cannot be used (unless both the gears are replaced).

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.

Off track entirely, Eohippus, The beautifully named Dawn Horse

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

Apparently the Megatherium was a prehistoric giant , elephant sized, sloth. Wonder if the original namer was thinking of Hyraxatherium, the first horse?

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.

I have come across an anomaly with the Dennis gear drawing. The one I have shows 37 Reinecker teeth, 6Pitch; however it also states an OD of 6.4284". Obviously we would expect it to be 6.5" ((37+2)/6). The pitch diameter is stated at 6.166 as would be normal (37/6). Obviously I now need to get the gear pair out to measure but does anyone know why this smaller OD would be used?

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.

The tractor version were called 'Rotapeds'.

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