Tufnol (Textolite) as a material for pulley

I need low inertia pulley, eg ones made of low density material.

I was searching various grades of aluminium but required bar sizes are available ex stock only in soft grades which wear easily. I am not equipped well to cast one myslef albeit this will change - conversion of microwave into nonferrous metal smelter is under way and initial tests are promissing (sample of silver was smelted).

Meantime I have Tufnol block of adequate size to produce what I need.

What do you think about Tufnol as material for a pulley? It must have good tribological properties if gears are made of it (including gears of tumbler reverse on my ML7).

My concerns are about coupling Tufnol to steel shaft. Keyway in tufnol might get damaged by steel key. Should I make a Tufnol key as well or is it better to bore bigger hole in the center and fit (glue permanently) metal ring with a bore to adapt shaft?

Martin

Hi Martin you don't give a lot of information on what sort of pulley . Belt, V, multi V, diamiter and speed. Jones and Shipman in eternal grinders have a flat belt tufnol pulley running at very high speed.

David

It will work with 10 or 13 mm V-belt at effective diameter of 6" and maximum speed 1450 rpm. Single belt, expected to transmit 1/2-3/4 horses.

Martin

Prepare fro dust when machining. When I did a big quantity for someone years ago even with a woodworking style vacuum sucking a tornado and bowing the dust outside enough escaped to put a red film on everything in the workshop that took years to finally remove.

Tufnol gears are often used in a changewheel train to reduce ringing and I think the Meddings drills have one in the backgear. However there are different versions and some 'grain' so select with care.

Hi Martin,

If its any help, the old Westland Wessex helicopter used a Tufnol pully as a cable tensioner in the flying control system.

It did have a central bore made out of an alloy, with a sealed bearing running on a fixed steel pin.

The cable was approx 3/16 " diameter steel.

For your application I would suggest a similar bore arrangement but without the bearing, say, a brass keyed hub?

Regards

Lofty

You should look for the cloth type Tufnol and not the resin paper type. In fact if in heavy duty or high speed use a bush in the center, perhaps flanged and pinned.

I had one as a timing gear in an Opel Kapitan and it sheared teeth way up in the NFD in Kenya, the replacement was an Alu. one.

Clive

Depends on what tufnol you are using. I machine Tufnol Whale for bearings & it comes off in long strings which I have to keep clearing. Certainly no sign of dust.

I would certainly go for the steel bush option if using Whale but I do not know the version of tufnol you have

Add to above. Textolite is apparently a fabric based material but various fabric is used and the resin varies as well.

Can you not get the harder ali in 10 or 12 mm plate rather than bar?

Hi,

Thanks for comments, all of you.

My Tufnol is "cloth type" and it gives away lots of dust while turning. It turns brilliantly apart from the dust and it seems to be hard, certainly better than crap (eg easy available) grades of aluminium.

NB. I do not understand why commonly sold grades of aluminum bar are basicaly good for nothing apart from generating hydrogen via reaction with solution of caustic soda if at very little or no additional expense a reasonable material could be made.

So base on what you say it seems reasonable to produce larger bore and install keyed & flanged brass/bronze/steel bush press fitted in presence of retainer (Loctite?). I will proceed that way.

Martin

It will be 2 step pulley working with 10 or 13 mm belt, so the plate would need to be more than an inch thick.

Martin

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Martin,

I'm struggling to find any supporting evidence for that closing assumption:

" ... if at very little or no additional expense a reasonable material could be made."

I suppose it depends on your definition of 'a reasonable material' but the manufacture of the better Aluminium alloys is certainly not a trivial matter.

MichaelG.

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http://www.raaltd.com/aluminium-plate.html#casttoolingplate

Edited By Michael Gilligan on 25/03/2018 10:38:55

Why not consider a 2 piece pulley & pin together? That way the plate need only be slightly above the width of the belt.

Aluminium grades - which type do you find difficult to machine? Many grades are gummy with tools aimed at steel. Use of the right lubricant or carbide inserts makes the stuff machine well. One of the engineering skills with aluminium is using the right grade in the right place. Something like 1050 is the metallic equivalent of cream cheese, and works well where you need cream cheese. Same as with steel, you'd not use a hardened bit of silver steel where mild would do, and vice versa.

Regards

Richard.

Yes but basically 3 versions are available.

1. Glass fibre reinforced - More suitable for NASA but also used in printed circuit boards working in high temperature (grades resistant up to 250*C are available).

2. Cotton cloth reinforced - suitable up to 120*C used in general engineering like gears etc.

3. Paper reinforced - marginally weaker than 2. but still excellent.

Resins do vary but they are generally phenol - formaldehyde polycondensates of comparable properties. Sometimes melamine-formaldehyde polycondensates are used but such products should not be called "Tufnol" or "Textolite" and are yellow or whitish rather than brown.

Resins are engineered rather for chemical and thermal resistance.

When heated characteristic smell of phenol and/or formaldehyde can be felt.

Martin

Can't see you wanting much better than HE30 bar (6082) or as MG has just beaten me to it, Tooling plate. Cast alum would probably be HE9 grade which is like machining putty.

Regards Ian.

http://tufnol.com/materials-full/materials.aspx      What grade do you want?

Edited By Circlip on 25/03/2018 10:46:56

Tufnol are very helpful if you ask their technical department. I many years ago worked close to the Tufnol works and could call in to ask recommended grades for my application, sometimes coming away with a "Sample" I suppose those days are gone now though. I don't subscribe to your theory on grades of aluminium they all have a purpose especially if welding is involved.

This 1050 grade is widely available and at least in my opinion it is good for nothing.

I do not have any difficuty in machining it but parts made of it do not last long, so they are best if not made at all.

I love 7xxxx grades as some of these are very good but it is not easy to get them. Silumins are OK but until I have adapted my old microwave for smelting them, they are not usable for me.

NB. converting microwave into smelter is an interesting project of its own and not costly either. I can already smelt 10-20 grams samples of silver there but some more permanent thermal insulation of walls and door is needed for more sensible quantities. Bonus is that it could allow for smelting under argon to produce quality melts if necessary or should be usable for brazing in inert gas, eg there won't be scaling, I hope.

Martin

Adding 2% of copper is not a great expenditure, yet for some reason 1050 prevails.

Martin

All pulleys on control cable runs on any aircraft I have worked on(mainly Cessna, Piper, AS types using AN numbered parts), and others I know of use Formica (similar to Tufnol) pulleys. They are molded to shape rather than machined, and are quite durable.

Ian S C

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Returning to the opening post ....

If you need low inertia; there is, of course, an alternative approach:

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

and, if you need to further reduce inertia; it would be worth considering a conversion to variable frequency drive.

MichaelG.