Making G80CS flywheels

[Triumph-Legend]

The Wolf flywheels are made from EN26.

I have been loaned a set of original short stroke wheels which i will get spectro analysed.

The wheels in my failed crank appear to be mild steel.

Well there you are then. Don't use mild steel. Go for something tougher.

Getting a lump of 50 year old steel spectro analysed. That will be interesting. Please post the results. (probably a mix of metal swarf sweepings and wood glue)

The interference fits are much greater on the factory wheels than the Wolf wheels. Both have excellent surface finishes in the bores.
By interference being greater, I assume that you mean that there is a greater tolerance on the fit. This I can easily believe given that the factory were probably still using machinery left over from WW2 production. As you are aware, modern machinery with DRO / CNC control can easily hold far closer tols. I would go with the tighter tol fit and a tougher material. Why not, the machinery can easily machine to any tol size you decide.

Do apply radii/chamfers at shaft fit edges to ensure correct seating.

Just a note: Fifty years ago I worked for a piston manufacturer that was still using WW2 era ward capstan machines. About 12 years ago I passed a large Herbert capstan lathe onto a friends machine shop. They needed to drill and some bloody big holes into some large bar stock. Again the machine was WW2 era and still doing a good job.

[Braaap]

Radius the edges to suit shaft corners. Jolly good point thank u.
EN26 is some nasty stuff. One web page i refered to gave 4340 as a lesser equivalent.
4340 isñt very friendly to machine either and would be well up to the task. At this stage it would be my choice.
Cut a couple of discs from 200mm round bar mite be a better way to go... and put the holes in manually.

The "greater interference", i refer to; the wolf big end fits have 0.001" interference. The used factory wheels have 0.003" press fit.
Perhaps the gnarly EN26 is best at the lighter fit?

[vincentvv]

Glad we have a member like you who can enlighten us with more mechanical knowledge then.

[pkr87]

Triumph Legend. Nothing to do with flywheels. By the way I could measure some of my flywheels but would not know what material they are made of so did not answer the rude New Zealander. In the mid Fifties the factory at Plumstead had nearly all their machine tools replaced with brand new Herbert equipment, at huge expense, so it is unlikely that they would have been using any ancient machines. Nothing wrong with old machinery, my pillar drill is ex Chatham Dockyard and was made during the First World War and is still reasonably accurate.

[Triumph-Legend]

Triumph Legend. Nothing to do with flywheels. By the way I could measure some of my flywheels but would not know what material they are made of so did not answer the rude New Zealander. In the mid Fifties the factory at Plumstead had nearly all their machine tools replaced with brand new Herbert equipment, at huge expense, so it is unlikely that they would have been using any ancient machines. Nothing wrong with old machinery, my pillar drill is ex Chatham Dockyard and was made during the First World War and is still reasonably accurate.

Thanks for the info. I stand corrected.

However back in the fifties the machining parts still relied on the skill of the machine setters and the person winding the handles. No DRO's nor CNC back then. Yes gauges were and still are commonly used but to some degree the use of the gauge was dependent on the feel of the fit when checking the part produced. Believe me after the fourth pallet load of parts one really did not pay too much attention to the fit being a bit on the loose or tight side. Also it was not unknown for the adjustable type gauges to move a bit in use. The trick is for the design of the product to accommodate the greater tolerance an still work OK. It also explains why modern engines work so well. They are simply made better both in terms of materials and component fits.

[Triumph-Legend]

Radius the edges to suit shaft corners. Jolly good point thank u.
EN26 is some nasty stuff. One web page i refered to gave 4340 as a lesser equivalent.
4340 isñt very friendly to machine either and would be well up to the task. At this stage it would be my choice.
Cut a couple of discs from 200mm round bar mite be a better way to go... and put the holes in manually.

The "greater interference", i refer to; the wolf big end fits have 0.001" interference. The used factory wheels have 0.003" press fit.
Perhaps the gnarly EN26 is best at the lighter fit?

If you think about it, the tolerance given make perfect sense given the manufacturing methods used back then. Assume nodular cast iron flywheels. Quite soft and easy to machine. Internal bores most likely finished to N5 or close to. 0.003 would be fine allowing for some surface deformation of the material.

Now go for a harder material, say EN24 and a surface finish of N4 or better. Modern machining methods and surface finishing will make a significant difference.
A standard interference press fit. For reference by members here is a link to a site explaining shaft / hole fits and tolerances. (not to tech and a good explanation).
http://www.cobanengineering.com/Toleran ... ndFits.asp

As mentioned previously, make sure that any radii or edge chamfer clears any internal corner radii on the shafts.

All you need now is a big old lump of metal. Have fun and don't forget to post a picture of the finished assembly.

[SPRIDDLER]

However back in the fifties the machining parts still relied on the skill of the machine setters and the person winding the handles. Yes gauges were and still are commonly used but to some degree the use of the gauge was dependent on the feel of the fit when checking the part produced. Also it was not unknown for the adjustable type gauges to move a bit in use. The trick is for the design of the product to accommodate the greater tolerance an still work OK. It also explains why modern engines work so well. They are simply made better both in terms of materials and component fits.

I don't wish to be drawn into a deep discussion on the topic (because I don't have sufficient engineering expertise) but it reminds me of comments by Bert Hopwood in his gripping book 'Whatever happened to the British motorcycle Industry' where he claimed that much of the success of the Japanese manufacturers was their ability to produce components to consistently fine tolerances. This meant that they could provide a superb global spares service of shafts, gears, pistons etc. to foreign dealers and owners who previously (according to British bike Owners Manuals of the 50's) were required to return their engines to the factory for parts to be matched.
In a fascinating (to me) interview in 1954 a Mr P Walker, the designer of the 350 and 500 H/W AMC engines, admits that parts were graded by size tolerances and 'matched' on assembly. The article can be found here: http://archives.jampot.dk/editorial/Roa ... _Baker.pdf

Here are two examples:

Tolerances. Heavyweight engine..JPG

Tolerances .2 Heavyweight engine..JPG

[Braaap]

Great resource thank u Spriddler.

To answer TriumphLegend... the original CS flywheels are steel. But what steel?
That aside... your observations re materials, finishes and fits is bang on. Thanks.

All the ducks are starting to line up.

Giving thought to getting 2 x 30mm thick slices of 200mm 4340 round bar...

[MalcW]

I have posted half a dozen times. The silence has mostly been deafening.
In my other life i ride a Ducati. Online help is abundant and forthcoming. Friendly chat is offered by riders without the specific answer.
Perhaps the difference is "Facebook"?
As a new member here i have been disappointed.
If this is the spiritual home of AMC worldwide.... we are in trouble as a marque.

Just telling it how i see it.

I have found that whenever I have asked a question, I have had responses from those with something useful to say. Others have remained silent, which to my mind is far more useful than the server getting clogged up with dozens of replies to each and everyone's query along the lines of 'I don't know, but best of luck'. I have posted a couple of queries with zero replies. I take that as meaning that no-one has the answer, and not upsetting myself by assuming that no-one can be bothered. Perhaps Ducati folk have more time on their hands?

With regard to this specific query, you seem to have far more specialist knowledge of this subject than most other people here, to the point that we should be coming to you for answers.

Malc

[Braaap]

My comments came after other posts re more general issues.
You are quite right this is a curly one.

My comments still stand however.

As a group we could learn from more vibrant forums?

Just trying to help ☺
Awareness is a good thing