andypugh

If that doesn't do the trick I found a trick for boring tapered holes with a boring and facing head: http://www.cnczone.com/forums/vertical-mill-lathe-project-log/109301-cnc-3.html#post1357394 Though that part looks just about small enough to (with great difficulty) mount on a lathe.

I got the castings back at the weekend: https://picasaweb.google.com/108164504656404380542/Holbrook#6230479127730875154 I don't actually know what the total cost was, I just realised that I haven't paid for them.

Amusing to see a solid-tyred vehicle delivering a load of pneumatics.

Is he intending to partially dismantle it and hide various parts in fields around the country? It looks complete to me, certainly compared to most of the projects on here.

I would do it cold, then there is no rush. It's a small degree of bend. It might still be worth jigsawing the template just as a reference.

I think we can be pretty sure that the device being described is Pre WW2. Almost certainly Pre WW1. I wouldn't be surprised to find Pre Boer War?

Band brakes by any chance?

I was told many years ago that they are illegal to use in the UK nowadays. (this makes some sense, poking holes in tarmac is likely to be unpopular). So you can probably have them fitted, but shouldn't deploy them. Not directly related, but I did a trailer-towing course over the summer, and one useful technique taught there was to deliberately jack-knife the trailer if you are having trouble getting going on a steep hill, so that you can get the towing vehicle rolling and the clutch engaged before the trailer starts to move. (My job sometimes involves towing special trailers up the highest mountains we can find): http://mustangae.com/products-services/towing-dynamometers/carsuv-tow-dynamometer/?prod=Car%2FSUV+Tow+Dynamometer

Thinking about Barry's pictures of 3D-printed patterns reminded me of another process that is very applicable to the vehicle restoration game. We actually have one of these machines at work, but I don't get to use it. Excess capacity on the machine is sold via an intermediary company. When I enquired about Dennis cylinders they estimated around £10k for two cylinder blocks, starting from a CAD model.

Interesting to see when I started this, it seems like months that I have been at this, and it is. These are the patterns, almost ready for the foundry. https://picasaweb.google.com/lh/photo/gQuPtDB0J_ZiqVVDHaf8vtMTjNZETYmyPJy0liipFm0?feat=directlink

Aha! I found that I mentioned it in the blog post that describes making the brake. http://bodgesoc.blogspot.co.uk/search/label/Neracar9 This is a transmission brake just like the Thornycroft one, but just a little bit less hefty :-) (And the answer is 200C)

I don't remember, but it would have been whatever Saftek suggested. Probably on the phone, I can't find an email.

I bent mine in the oven, as suggested. I put them in the oven on top of a former, then took them out and pushed them onto the former with a tea-towel. However, if I was doing it again I would not heat the former, as it took a long and uncomfortable time for things to cool enough to take the set. I think hot material onto a cold shoe would be better. You can always have a second attempt.

Now, if only you had just built a nice big shed at the side of your house, then you could put a decent-sized lathe in the end of it. http://www.ebay.co.uk/itm/181925330600 looks to be shorter than a Dennis is wide (though he does say that the photo is not necessarily of the lathe he is selling)

You quite often see brass fitting soldered to steel tanks, so I don't think this is a huge concern, especially in a part that probably doesn't see such a huge temperature swing.

I used similar "hybrid techniques" to make some Ner-a-Car parts. The material was rather thinner, I suspect. http://bodgesoc.blogspot.co.uk/2014/07/neracar6.html

Possibly outside the capacity of your laser-cutterist, but if you had done the whole form in steel plate then that opens up the option of heating the flange with a blow-torch to make it easier to shrink the ripples out. It isn't like some mild steel discs are going to sit around for long without finding other uses, is it :-)

The fire-engine had had brake linings retrofitted to the shoes, and that meant that the working diameter was wrong. I changed the radius of the metal shoes to partially correct this (using my dad's horizontal boring machine), then bored out the relined linings to the correct radius to complete the job. In principle you could remove the drum from the gearbox, set the gearbox up on a boring machine, clock true to the output shaft then bore the shoes to the exact diameter in-situ. An alternative, though not so accurate, would be to wrap a spiral of emery tape round the drum and apply the brake. The problem is the lack of ideal inelastic zero-thickness emery tape.

Yes, a fair bit. I basically made a spring, worked out how much bigger it was than I wanted, then turned down the mandrel to compensate. The final springs are here: https://picasaweb.google.com/lh/photo/u7-LoyIMofVXAlpzdUO_z9MTjNZETYmyPJy0liipFm0?feat=directlink The mandrel included an attempt to form the bottom loop, as the springs are a funny-shaped motorcycle seat spring.

Ah, yes, it all makes sense now. I wound some 1/4" springs last year, but there was no way to do those by hand without being maimed, so I improvised: When I bought the milling machine I was sure I would never use the 45rpm speed.

There shouldn't be any need to heat-treat piano wire. It gets its properties from cold-drawing, and heat treatment will destroy that. The heat-treatment stage of piano wire manufacturing is prior to the cold-drawing (or cold-rolling) process and is called "patenting", where the material is heated to the austenite transition temperature, then quenched in molten lead or molten sodium hydroxide to transform to fine Bainite. Cold working of this then gives a very high tensile strength. Quenching and tempering will give you reasonable properties as it is high carbon steel, but the chances are that you had a better spring before the heat treatment. Suspension springs are heat-treated, they have a large section and no scope for significant cold reduction. (This was my "specialist subject" for 2 years at Leeds)

https://en.wikipedia.org/wiki/Holt_tractor Seems to suggest that the front wheel was a Holt 120 feature and the 75 was steered by the tracks only. Is this correct? It doesn't necessarily look to be, after googling round the subject. I suspect that the Wikipedia page needs help, it sounds like it it saying that the front wheel or the tiller were covered, when it probably means that the whole tractor was.

Just checking. Failure of that component could be quite exciting :-)

What material? I would be a bit nervous of using cast iron in that application, though ductile iron or ADI would be fine. (I did some fatigue testing for JCB on ADI in a previous life, and it's amazingly strong and tough)

Something else you can do in CAD and not in real life is put your pattern in your core box to test that everything is in the right place (not trivial when everything has had drafts added) This is the core box lower. I now need to decide how to make it. Also, you can analyse the overlap between the parts, and that is what the actual casting will be (I am not sure about the volume calculation, that sounds like a 112kg casting...)