Here is a list of all the postings David Fox 3 has made in our forums. Click on a thread name to jump to the thread.
Thread: Simplex machining the pieces. |
15/02/2018 11:04:38 |
Last year I decided to make the Simplex 5 inch gauge tank engine. It was described as a beginners locomotive. Now I have been on a very steep learning curve and have produced a very high quantity of swarf and various paperweights which now stand on the sill in the shed! BUT I am learning and slowly progressing in my task. But certain items are, I'm sure, there to defeat me. One is the axle pump. Now the pump itself although it holds a few large challenges is not the problem but the outlet tee is. It seems to combine the top of the outlet valve the two outlets and nut to tighten it down all in one piece. How are you supposed to machine an item like that and when tightened down it points in the right direction? Is it supposed to be silver soldered from more than one piece of brass or what? In the book of words for Simplex - although I'm trying to build the later alternative pump - there are no construction details whatsoever! Beginners? Hoping for a positive response Dave F
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Thread: What have I done wrong?? |
29/10/2017 11:34:41 |
Thanks. It's too late to change the order of machining, and next time I will do as suggested, but the suggestion of tailstock support though is certainly worth doing. Thanks. |
28/10/2017 15:21:35 |
Well I've been busy in the workshop and I think - surprisingly - that it WAS the reamer as it seems that if I re bore the wheel it is again all ok. I mounted the wheel on the faceplate (thanks Duncan) centred as accurately as possible then skimmed the bore until a continual cutting noise was heard from the boring tool then one more fine cut passed through twice. I then used the old mandrel. There was sufficient mandrel stock left to remachine to the new diameter thankfully. Now all I have to do is machine the other wheels to the same size as the mandrel. So I'm using Bobs suggestion here. I still think it is a bit of a mystery, as each wheel was so similar, but why a four jaw rather than a self centring three jaw? Well the simplex wheels are just over the maximum capacity for that while the four jaw was ok - just. I was conscious of the dirty taper potential but did clean with cloth and finger!?! Thank you one and all for all your suggestions and I hope I can finish these wheels without any more fuss.
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28/10/2017 09:11:25 |
Posted by JasonB on 28/10/2017 08:58:13:
Has the mandrel that you made been removed and refitted to the lathe between making it and mounting the wheels. If it was not seated right when machined or ha snot gone back in the same then that would give a constant error on the wheels. Is there a slight radius on your mandrel where the spigot meets the flat face, often left by an insert tip, if you the edge of the holes needs to be chamfered/CSK to clear that and allow the wheel to sit down flat I would have thought movement in the castings would not be the same for all wheels. Easily checked by placing the machined face on a flat surface and see if it is shaped like a Pringle. Also not sure chuck jaws would cause the issue as the surface and bore would be true to each other as machined at one setting no matter how wonky the wheel was mounted. You could check the bore is true to the machined face by turning the end of a bar to a good push fit in the 11/16" hole and then without removing from the lathe push on a wheel and see if it runs true. Great thoughts. Will report back in a couple of hours when I've been in the workshop. I did use an insert tip but. Cut slightly further and use its side face to give a slight inner taper on the mandrels side thus avoiding that small radius if you get my thoughts!!
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28/10/2017 08:54:33 |
Posted by Chris Evans 6 on 28/10/2017 08:52:34:
All is not lost. There should be enough metal in the bores to true up to 18mm after all you are making both parts so can use whatever size you want. Thanks. I think this will have to be the way forward! |
28/10/2017 08:52:53 |
Thanks it certainly seems to have released some stresses. But mine have gone through the roof. Bizarre! |
28/10/2017 08:46:18 |
That's what I would have thought but surely if that were the case the rear face of the wheel would be slightly off or am I making assumptions here? |
28/10/2017 08:31:32 |
Hand held. But all the wheels are exactly the same. |
28/10/2017 08:03:20 |
The six wheel on the Simplex shouldn't be too difficult surely? I am fairly new to model engineering but thought this should not throw up any great problems. I mounted each of the castings on a 4 jaw independent chuck and faced the back of each. Then whilst still in the chuck centre drilled then drilled through with a 1/2inch drill. Then bored it out to just under 11/16" and finished off each with a 11/16" hand reamer. I had bought a 3mt soft end 40mm x 40mm arbour which I turned down 15mm of which to be a tight fit on the newly bored and reamed wheels leaving a shoulder to support the back of each wheel. I then tapped an M8 thread in the end of the arbor so a bolt could then hold each wheel firmly in place. On trying the wheels on the arbor they fitted perfectly sliding on tightly with a little friction but on running the lathe the rim of each wheel moves from side to side by about 2mm when firmly against the shoulder! WHY? What have I done wrong?
2 The lathe is a Seig SC4 about 8 years old but not at all heavily used. The wheels cast iron and the 3 mt stub bought recently from the midlands model engineering exhibition. Any help gratefully received!
Dave F
Edited By JasonB on 28/10/2017 08:19:03 |
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