dave windymiller

Hi Danny The metals are nothing fancy. Dural (duralumin) is simply a tougher grade of ally but normal ally should suffice and would be lighter. I had dural kicking about as it was once part of a wheely bar from a drag bike. The metal for spinning is just bog standard 1/16 ally sheet (dont know what grade). I have made spinners using glass cloth (having made a mould from a vac formed version) but with the same back plate idea. Heres my mossi. These spinners withstood a vertical crash into the soft field after the usual tip stall that mossies love to do so much. Thankfully, the repairs to the plane only took a week. Dave   Edited By dave windymiller on 21/05/2018 23:09:37 Edited By dave windymiller on 21/05/2018 23:11:42

To make the backplate True up a rough cut peice of 6mm dural using a 6mm hole and 6mm screw to hold it in the lathe. Once round it can be removed and a better, more accurate method of holding it will be used. Put a peice of scrap thats smaller than the spinner into the lathe and true up the front face and add a shallow 8mm hole After degreasing, attach the backplate to the newly formed face using thin cyno and a tailstock centre to get it reasonably true. The faces should be very true if alls well and the o/d can be also trued up. Dont remove this from the chuck until all machining is done. Set the tool stock to an angle that suits the spinner at the base. Machine away the o/d until the spinner fits over the backplate. Leave a 1.5mm shoulder for the spinner to seat on. Take off just enough for the spinner to seat against the 1.5mm shoulder. It should sit nicely and be a tight fit that holds itself on. All being well, the spinner will spin true!  The shoulder edge can be trimmed to match the spinner either using the same angle or at 90 degrees as preferred. Machine away the centre to leave a 1.5mm backplate and a 3mm thick outer ring where the spinner fits. Also open up the centre with a boring bar from 6mm to fit the engine (1/4" in my case). It can now be removed from the lathe by heating with a blowtorch until the cyno fails. Clean up the back of any cyno that remains.   Final instalment soon! Edited By dave windymiller on 20/05/2018 22:54:45

Again thanks for the complements and good luck with the albatros spinner. I guess this is posted in the right place already if rcm&e wanted to do an article and i would oblige if asked even if i am just a garage bodger type chap with improvised equipment. I will finish the spinner article soon, just got back from a walking holiday so i cant walk now!!

thanks for the complementry replys folks. Bit side tracked at the moment with holidays and work so will do the last bit in about 2 weeks! Dave

If the safety of flying is expressed in terms of death per mile travelled, a trip to mars using the same figures will result in only 2 out of every 3 trips getting there. Dont know if the above is true as i cant be bothered to research it but when i heard this it made me smile how statisitics can be manipulated. Flying is so dammed dangerous.

Rotation speed. Ive read it should be 800 rpm for initial roughing and 300 rpm for finishing. I use a lot slower speeds and it seems fine as my lathe lacks power at higher rpm. If you have judged the size of the disk correctly, there would be nothing left as you cover the mandrel. If its too big you will end up with some excess that can be cut off with a lathe tool. Hopefully the spinning is longer in length than the final spinner so it is a simple case of trimming the excess and making a neat edge. You can also remove the concave washer and neaten up the centre if necessary as the metal should now be a tight fit on the mandrel. You can also spin the metal over the back edge of the mandrel so it becomes permanently attached allowing you to give the centre more work with the tool if required. Once done part off the spinner to allow it to be removed from the mandrel. If you managed to spin a sufficiently thick layer onto the mandrel, there should be enough material to allow any scratches to be polished or even machined out! Final section – making the backplate and attaching the spinner.

The first task is to cut a blank disk of ally about 50-70% bigger than the finished spinner. Try to make the blank reasonably round and smooth as jagged edges can act as a focal point for the metal to crease. I used 1.5mm or 1/16 inch thick ally. Next task is to anneal the ally. This has to be done several times during spinning. I just do it till it looks hot enough but you can use soap as a temp indicator (when it turns brown when its done apparently). The blank has to be attached to the mandrel. For my turbine, all the parts I made didn’t use the centre so I could easily drill and screw the blank to the mandrel. The ME109 has a hole for a cannon in the centre so I also used a single m4 screw to attach the disk. To spread the load I made a 20-mm washer with an inside concave shape that matches the centre of the spinner. If you don’t want a hole in the centre, the usual way is to use a live centre from the tail stock to physically push the disk/ concave washer against the chuck. Unfortunately my lathe isn’t able to do this as the headstock uses a taper plain bearing and any excess load from the tailstock causes it to sieze! Good job it’s an ME109 spinner with a hole I’m making. The tool I use for forming is a brass rod approx. 12mm dia and some 600mm long with a file handle at the end. You could attach a small piece of brass to a steel rod of course. Cut the end of the tool at an angle, round all edges and polish it smooth. You can also use ball races with a radius ground on one edge mounted in the toolstock or on the manual tool. This is better for stainless ive found but for ally I prefer the brass rod method. This is used with a lubricant to keep the brass and ally from knarling together. Motorcycle chain lube works for me but candle wax or tallow can be used. To lever the tool against the ally I use a bar mounted on the tool stock with holes in for a peg to sit in. This can easily be altered to get good leverage. The tool is used against the ally UNDERNEATH the chuck. This way if you were to catch the chuck it wouldn’t fire the tool towards you. I must stress here that spinning probably breaks all the rules you are given for using a lathe safely!!! When spinning, there are two different approaches. If you force the ally around the mandrel whilst keeping the ally disk flat/radial, you are in effect pressing the mandrel through the ally and extruding it. This thins the ally much like pushing your finger through taut rubber sheet. Any section that’s parallel will get too thin and probably sheer off. This pic shows this effect. The other way is to “lay” the ally onto the mandrel by forming it into a cone (similar to the drawing at the top of the 1st posting) and done by sweeping strokes towards the outside of the disc. Unfortunately, if you wrap a sheet of paper around the mandrel it will wrinkle and crease which we don’t want. Spinning is therefore a mixture of the two methods above. We want to lay it down to keep thickness but have to extrude it enough to keep it from wrinkling. You are in effect moving the metal about like clay on a potters wheel! The first version of the spinner I made, I extruded it too much and ended up with a spinner 0.6mm thick (too thin). My next attempt resulted in a 1.6mm thick spinner, much better! During the making of my second spinner, the ally started to wrinkle which first shows as a judder felt through the tool. Don’t try to get rid of it by carrying on, it rarely works. It’s a good time to take it off and try to minimise the wrinkles with a hammer. It doesn’t have to be perfect, just remove the worst of it and re-anneal. The wrinkles are then removed by concentrating the force at the mandrel to extrude, ie push the cone further to the left. This action should cause the cone to open up and the wrinkles disappear (or it ends up a knackered mess ready for the bin!) Its very difficult to put this whole process into words you just have to try it and spot the various behaviours for yourself.   Edited By dave windymiller on 04/04/2018 20:23:14