Tufnol (Textolite) as a material for pulley

Tufnol is good for pulleys but you say low inertia, which to me suggests rapid starts and stops, in which case extra care will be needed to stop it shearing perhaps a top hat sleeve with multiple dowel pins?

As for aluminium alloy, 90% of the stuff out there is 6082 which has excellent general purpose properties and is both affordable and easy to work. Your experiences suggest you have been using near-pure aluminium (1000 series). Search on 6082 alloy and you will be OK.

Neil

Martin: You must be looking in the wrong place?

Grade 1050 is almost pure aluminium. It is 'orrid stuff to machine, think warm fudge. However, as far as I'm aware (at least from my professional aluminium stockist) it is only available in sheet form. Not surprisingly it is intended for sheet metalwork where it bends without cracking. Any of the common aluminium alloys such as 2014, 6082 or 7075 are available in plate and bar, and machine well. By far the most common alloy (6082) has a good combination of strength and machinability and is widely available from a variety of sources ranging from professional stockists to Ebay.

If you really need a low inertia pulley make cutouts, like a flywheel.

Andrew

Surely the problem with Tufnol is delamination? Lovely for a toothed belt but no good for a vee belt because that will wedge it apart in the direction where it cannot resist

Cloth type Tufnol will likely be fine. I used to have a load of keyed Tufnol gears I acquired in an industrial scrapyard and they were clearly capable of demanding application given how they had been used.

Not easy for anyone to make a meaningful recommendation though from the sketchy information given. I used a Tufnol for a variety of vee pulley applications without issue but I didn't do any proper design calculations and they probably weren't close to their limits.

If you have a suitable sized piece, I'd just get on and machine it up. If you were up to doing the appropriate design calculations you'd probably have the answer by now.

Murray

Here you go bit of mgAAOSw8GFanBVI">7075 plate 12mm thick off e-bay. You will get a 6" and a 5" disc out of that and just pin or screw them together. Saves having to make a hub and you can cut your keyway straight into the built up pully. Same seller has lots more 15mm thick too.

how about adapting a wheel from a child's scooter, bike, pushchair etc.

'This very useful for sheet metalwork with 0 corner radius. Best if sheared. Easily formed, cut etc.. Not wildly useful aside from that, I admit.

Your idea of a microwave furnace is interesting. I have not done anything that sophisticated. I made myself a little furnace using scrap stainless ducting and lined it with £2 of concrete. It's now needing re-lining after 15 years. I have used coal, charcoal and pallets as fuel. At best I can melt 2lb of aluminium in15 mins. With the microwave, if you have much metal in the crucible, there must be a concern over radiant heat igniting something - sure I'm telling granny how to suck eggs, but domestic microwaves are not meant to hold something that hot. The heat radiated from the crucible when withdrawn from my furnace is really quite astounding.

Regards

Richard.

You need to insulate microwave walls and door with light heat insulating material which is used also for thermal insulation of fireplace. this material is cheap and very easily formed.

Alternatively you can purchase similar looking material used in furnaces.

Both are wonderful heat insulators.

You *must* ensure that your product is microwave transparent, eg it does *not* get hot when stuffed up to microwave. After few minutes it may get a little bit warm but nothing more than that. In any case avoid running microwave on no load for more than 2-3 minutes or you may damage magnetron and other circuitry.

To join pieces of insulating material you may use an adequate fire resistant cement. Cement also must be (when dry) microwave transparent, test it as your insulating material. Appropriate cement is alumina based and certainly *not* zirconia based as the latter will absorb microwaves and get very hot and it is not what we want.

Make sure that thermal bridges are absent, eg that thermally insulating layer is protecting entire interior and door. 25mm of meticulously fitted insulation from all sides will do if you are not aiming above copper or gold (1100*C) and do not intend to run extended sessions, few hours long. Otherwise apply 50 mm thick insulation.

You must provide for pressure equilibiation measures.

Now you need a crucible and this should *not* be microwave transparrent. The best (and cheap enough) are *carborundum* (silicon carbide) crucibles and preferable variety is one nitride bound but others are also good.

Another and more expensive option are those made of zirconia.

You will recognize suitable crucible by observation that it gets very hot once stuffed to microwave. If left too long it will get red hot and damage not thermally insulated microwave. Fire and property damage might result.

To reduce risk of fire it is also of paramount importance to use new or exceedingly well cleaned up microwave.

Now fill scrap metal to your crucible and stuff it to microwave. My initial trials were done in block of mentioned insulating material and silicon carbide crucible. Microwave is not lined up with insulation like described but a block of insulating material encasing crucible from all sides is good enough for prove of concept experiment.

20 grams of scrap silver was smelted within 20 minutes in 800 W microwave. Beauty of this setup is that most of microwave energy is going only into crucible and its load.

If you want to use microwave as a muffle, stuff few lose silicon carbide heating elements in. You will get hot chamber this way.

There is much more to it, above are explained only basics sufficient to get one going.

I may write something about it in the future, once some basic work to develop this tech is done. For example flimsy plastic parts in door will need replacing with something sounder, inlet and outlet of inert gas is to be installed etc. Interlocks switching off power upon opening of door should be kept and after any modifications of the oven one must ensure that microwaves do not leak out etc.

Some basic setups working with household microwave sufficient to melt a sample of glass are sold on Amazon. Search for "microwave kiln".

I am developing substantially better product than this.

Martin

I am currently living in Poland and they have what I described.

Occassionally, with much pain you can get 6xxx or even 7xxx but usually something very soft and useless is on offer.

Martin

Hi

"Converting the drive to Poly-Vee would allow the use of much smaller pulley diameters."

I agree with Michael Poly Vee drive is the way to go having converted 8 machines in the workshop.

Aluminium being the material of choice for pulleys. No apparent wearing even on a very old drill press that came from a busy engineering workshop.

Eric

Why not fill in your public profile? Then we'd know that, and we wouldn't waste time offering help you don't think you need.

Andrew

As a point of interest Ford V6 engines I worked on in the late 70’s had Tufnol timing gears on the camshaft mated to a steel gear on the crank.

Emco used Whale Tufnol for their FB-2 mill gearbox primary driven gear, the gear is a light press fit onto a straight knurled stepped hub.

I do import many things from UK, I have family there and also friends in academia and industry, spent most of my life there etc.

However items like bar stock is best to source out locally where you are. Sending small quantities will treble your bill.

Your ideas about suitable grades of aluminium are helpful but barstock of required diameter and of such grade is difficult to get here and for some reason soft grades of aluminum are commonly sold and these are of no use.

Martin

Hi,

I have surrendered and purchased appropriate block of duraluminium 2017A. Suppliers here in Poland were complaining that they have been tricked into buying a bad lot of aluminium which was not conforming to norms.

Perhaps cheap, cheap cheap mentality backfired.

Many warehouses were flooded with this stuff but now situation is back to something what was in the past a norm, at least according to their assurances.

So the pulley will be made of aluminium at the end.

Irrespective of this subject I have one more question about Tufnol.

How tough are internal threads in Tufnol? Eg would they cooperate nicely with M5 male screw applied without overtightening?

Martin

It might very well depend on thread engagement and number of threads engaged. High and plenty should be OK.

Ford V6 engines have tufnol cam gear drive the valve train and the do fail but only after high mileage.

The old V Fords (50/60s) used to also drive the oil pump from a tufnol gear. The splines used to fail, I understand. Whether the same shaft was driving the distributor, I cannot remember...

It would depend on the grade of Tufnol how well it would take a thread, I think the normal way of fitting screws in this type of material is to use a metal (usually brass) threaded insert.

Ian S C

I think you need to take account of the grain in Tufnol. For instance, gears are always made from sheet rather than rod. A screw thread might tend to delaminate sheet material but I've certainly had success with BA threads.

Rod