Flywheel turning hits a problem – 4 jaws to big!

 

Just had  a short session this morning and continued with the flywheel project for the Seal engines being built. However after getting the outside turning round and facing off I was left with 2.6315" diameter (need 2.5" finished size) so was pleased with progress. I don't know what specification the brass is made to but it machines great!

So feeling smug I thought I would rough turn the inside of the cavity (will be the rear of the finished flywheel) and using one of my home made boring bars before reversing the blank and bringing the front to roughly the correct diameter so that finishing cuts could be made all the better when running the lathe at faster speeds than the unbalanced blank would allow. This is when I hit a snag! One that I did not expect or had come across before using the Turner lathe.

The diameter of the cavity when finished, will be 1.75" and when I reversed the jaws, they were too big to go inside the cavity! So my smart thoughts went out the window! I will now have to remove the remaining excess by another method.

I did however resolve a question I had about the small diameter of the valve liners for the Seal. The answer came to me when studying the drawings last night and the reason is the need for the valve spring to sit over the outside of the valve guide. Mystery solved and I will just have to be careful when making them!

When I resume work on the flywheel I will hold the turned part in the 4 jaws as normal. A few photo's below show progress........

About Mike Freeman

Hello, my name is Mike Freeman and I am a retired Chief Fire Officer from the United Kingdom with a keen interest in model engineering, silver caddy spoons and sea fishing. I live in the pretty fishing port of Brixham, South Devon, in the United Kingdom. I am a sufferer of degenerative osteoarthritis, which impacts on the amount of time I can spend in the workshop, and is the reason why you will see seats and a stool in some of the photo's. I have only recently added the above sentence after a discussion with one of my Doctor's from the excellent pain clinic, based in Torbay. This does affect concentration one of the reasons why I double then re-double my measurements and set ups. Before completing nearly 30 years of public service I and my wife Sandy, owned and ran, a small restaurant in Okehampton Devon. Prior to marriage I worked for my father in his various businesses, in the early days these were garages, which he bought in a run down state, then built them up before moving on, to start again. I took every opportunity in those early days, to work in his workshop's learning 'on the job' rather than as an apprentice. This, I suspect, is the reason why my building various model's in the early days, turned into model engineering, when funds allowed the required equipment to be bought. My workshop comprises one half of a detached double garage. It has a stud wall separating the two halves and unusually perhaps, its own shower/toilet/washbasin compartment! (the true reason for buying the bungalow - don't tell the wife!!!) It is fully insulated with a ceiling and fluorescent lighting supplementing the one window. Several double electrical sockets are dotted around in relevant positions. Equipment consists of 2 lathes (1 Myford ML 10 and 1 Chinese variable speed motor with etched glass DRO's), 1 milling machine (RF25 far East) floor standing pillar drill, Proxxon bandsaw, Warco bandsaw, 6" wire brush and polishing mop motor, 6" coarse and fine grinder, Proxxon mini drill, various benches and an engineers vice. I have just acquired a third lathe, a Myford ML7 which I am at present evaluating so I can decide which of the Myford's I will keep. I have only just bought the Chinese lathe and had it fitted with DRO's prior to delivery. And what a bonus they are! So good in fact that I decided to buy another set for the Milling machine. Whilst my engineering experience can only be described as limited, I find the use of DRO's has affected my accuracy levels which have improved tremendously (although that's not saying much!) and would recommend their fitting to any model engineer. Prior to retirement I built for my son's 17th birthday a Locost car. This was a tremendous project and a great feeling when it passed its test. The book it was based on suggests it can be built for £250. Ours was nothing special in the sense of all new parts but still cost about £900 to build!
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5 Responses to Flywheel turning hits a problem – 4 jaws to big!

  1. Mike says:

    Why can’t you use a 3-jaw to clamp on the inside diameter of the cavity?

  2. Mike Freeman says:

    I can use a 3 jaw chuck as suggested, but the accuracy difference between 3 and 4 jaws is such that flywheel wobble is easier to create with three jaws, and I want wobble free flywheels!

    That’s not to say I won’t use the 3 jaw because the final turning will be made when the flywheels are mounted on a mandrel and turned between centres. I have yet to make my mind up as to the approach to take. Perhaps the first step will be to check the size the 3 jaw will take……

    Mike

  3. Dave H. says:

    Maybe a hollow aluminium stub mandrel to match the inside diameter (maybe 1/2 to 1 thou’ interference fit), with a shoulder for the faced end, brass in the oven, ally in the freezer, pop together and allow temp’s to equalise. That would leave the outer surface of the flywheel and the shoulder on the mandrel to check with the dti to true in the 4-jaw, then once you’ve finished (*Light* cuts!) either pop ‘em back in the freezer or machine away most of the ally then dunk in strong caustic soda for a few hours? Might mean sacrificing a chunk of scrap ally, though…. It looks like there’s not quite enough depth for an expanding stub mandrel, which was my first thought :(

  4. Ora Brymer says:

    Hello admin, I just wanted to give you a quick heads up that your Web address: http://mikes-models.com/blog/index.php/2010/01/flywheel-turning-hits-a-problem-4-jaws-to-big/ is being flagged as a possibly malicious web page in my internet browser firefox. I’d highly suggest having someone look into it. You can certainly lose a lot of guests due to this issue. Best of Luck.

  5. Mike Freeman says:

    Thank you but I don’t have it come up the same. Have you tried it in Explorer? I use Firefox myself and its fine.

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