Elliott 00 drive spline repair

[Wade BeattyParticipant @wadebeatty78296]

Thanks to Ian McVickers (https://www.model-engineer.co.uk/forums/topic/the-workshop-progress-thread-2023/) who had the same issue with his Omnimill 00 as I. The “drive ears” sheared off the plastic internal splined connection between the drive pulleys and the splined shaft of the mill vertical spindle.

A couple days later I had a new piece fabricated in aluminum in and back in place, I made 2 blanks but was tired of the project and did not broach the second but it is sitting in the drawer should there be a next time. Thanks to Ian for his post.

 

 

[Dave WoottonParticipant @davewootton]

Nice job, good to see some feedback on a post that helped a successful outcome, ready for another 50 years use.

[DC31kParticipant @dc31k]

Can we assume that the original machine was designed by a competent, experienced machine tool designer, and the components and materials designed (engineered) to give adequate service in an industrial environment?

If that is so, please could you outline your logic in choosing a different material for the piece you have made to the OEM original?

What has changed in engineering, metallurgy or machine design over the last 40-50 years that has made the original choice unsuitable?

[Wade BeattyParticipant @wadebeatty78296]

I have a bar of aluminum that was asking to be used, I don’t have whatever plastic that was available in the 70’s when this was manufactured. The plastic that was used is now hard and brittle (was that a design consideration?), I don’t think the qualities of the aluminum will change in the time I have left to live.

I have upgraded from a .55Kw motor to a 1.1Kw motor as has been discussed by other Omnimill 00 owners and I have surely worked this machine beyond what was originally intended, knowingly. Also carbide mills and insert tooling was not available as it is now.

I have made a vertical spindle support that steadies the column to provide for additional support and steadiness that was lacking even with the original hp motor.

I am a marine (chief) engineer that has had access to machine tools onboard ships since I was 19 years old.

And, I just wanted to. My machine, my choice.

 

[Wade Beatty]

On Wade Beatty Said:

[…]

And, I just wanted to. My machine, my choice.

 

Bravo !

MichaelG.

[DC31k]

On DC31k Said:

Can we assume that the original machine was designed by a competent, experienced machine tool designer, and the components and materials designed (engineered) to give adequate service in an industrial environment?

 

Well, we all know what they say about assume.

The plastic part was most likely designed by a production engineer (I assume!) because it was cheaper to produce than a metal part, not because it was the best possible choice of materials or the only choice.

In the home workshop I’d be doing it in aluminium too. Very nice job done there.

 

[John Doe 2Participant @johndoe2]

…….And, I just wanted to. My machine, my choice.

Well said Wade, and by the way; a really lovely job and a very good result.

Looks like an improvement on the original to me………..

[Paul KempParticipant @paulkemp46892]

Wade,

Did you make a drawing of it whilst you were about it?  If so I would be interested in a copy.  My mill was no spring chicken when I got it, still turns out good work and it’s done me very well on most of the bits for my half size traction engine – had to extend the table with a heavy plate when I machined to con rod!  Being able to swing and extend the head was a godsend!  Having the horizontal spindle also served well in cutting the gears!  It does have a rattle in the quill though depending on what you are doing and I am expecting it will stop turning one day!

Paul.

[Wade BeattyParticipant @wadebeatty78296]

Paul,

I will make a drawing up this week and post it for you. No problem.

 

Wade

[DC31k]

On DC31k Said:

designed (engineered) to give adequate service in an industrial environment?

You forgot “at a reasonable cost”. Injection molded plastics is very cost effective.

 

What has changed … that has made the original choice unsuitable?

That’s binary thinking. A more suitable option does not make the alternatives unsuitable, only less suitable.

[John Doe 2Participant @johndoe2]

Having thought about this overnight; I suspect that the original connecting sleeve was made from plastic for several reasons :-

a)  To provide a small amount of ‘give’ in the rotation; thus increasing resilience and possibly help reducing chatter.

And:

b)  To act as a torque limiting mechanical fuse, so in the event of a catastrophic jam at the cutting face, the plastic part would break and strip before any of the metal components of the quill or motor gearing could be damaged.

c)  It might possibly also have reduced noise levels and resonances of the mechanism.

d)  To accommodate small inaccuracies, (offsets), in the drive-train centre-line.

 

I think  b)  is the most likely reason. Sounds like a job for 3D printing !

[Wade Beatty]

On Wade Beatty Said:

Paul,

I will make a drawing up this week and post it for you. No problem.

 

Wade

That would be very kind, many thanks.

Paul.

[CirclipParticipant @circlip]

Correct answer JD2. NOT a cheapskate solution. What is the next weakest link in a jam up? How many 13A fuses are fitted to a 2A circuit? DoHHHHH

 

Regards  Ian.

EMCO V10 owner, (The one with the TUFNOL main drive gears)

[Circlip]

On Circlip Said:

Correct answer JD2. NOT a cheapskate solution. What is the next weakest link in a jam up? How many 13A fuses are fitted to a 2A circuit? DoHHHHH

 

Regards  Ian.

EMCO V10 owner, (The one with the TUFNOL main drive gears)

I worked on a few Ford V6 engines (2.5L and 3.0L) many years ago and the camshaft gears were made of TUFNOL.

[Michael Gilligan]

On Michael Gilligan Said:

On Wade Beatty Said:

[…]

And, I just wanted to. My machine, my choice.

 

Bravo !

MichaelG.

Agreed! 

[Vic]

On Vic Said:

I worked on a few Ford V6 engines (2.5L and 3.0L) many years ago and the camshaft gears were made of TUFNOL.

I had a number of Scimitars over a period of some 30 years and the early V6 3l engines had the Tufnol gear, all the later ones had a nylon outer bonded onto a cast iron centre.

Apparently the Tufnol ones used to shred teeth until the gap between missing teeth was too great at which point the whole lot dynamited.
The nylon ones worked perfectly until they didn’t – no warning, just disintegrated. The cam gears drove the camshaft directly and clearances were such that a gear failure ensured that every valve was thumped by the pistons – I had one let go at not much more than tickover and another at around 3500RPM – same result, full strip to remove the debris, full replacement set of valves.

[Nick WheelerParticipant @nickwheeler]

Another problem with the V6 Fords(the German Cologne family have them too) stripping their timing gears, especially at speed, is that the oil pump is driven off the camshaft via the distributor. I’ve seen a couple that killed the crank bearings as well as the valves.

[John Doe 2Participant @johndoe2]

Many many moons ago I owned a couple of cars with the “Essex” V6 engine, with the Tufnel cam drive gear.

One day the engine started behaving very strangely, and, combined with the auto gearbox, it was doing weird things, sudden power, sudden no power, changing engine speed with no throttle pedal movement etc.

In trying to find out why, I eventually took the cam gear cover off and discovered that the oval plate that held the camshaft into the block had become loose and had been allowing the cam to move forwards and backwards. Because the drive gear teeth were helical, this movement changed the camshaft timing and therefore the power and torque curves of the engine.

I think that…….ahem……..perhaps I had not torqued or locktited the camshaft oval plate bolts correctly during my rebuild of the engine, but luckily, the cam gear cover prevented the camshaft moving too far, and it stayed within a range such that the cam followers did not “fall off” the edges of the cam lobes – which would have caused instant destruction – but stayed working and moving the valves.

So I owned the first ever engine with variable cam timing – although the timing was completely random and uncontrolled and useless !!!

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