What did you do Today 2018

[SamsarandaParticipant @samsaranda]

Certainly look like Ariel cylinders, I remember reboring my Ariel Leader, back in the sixties, because it was rattling, that was a waste of time it was rattling just as bad after 1,000 miles. Wish I had the bike now, I used to commute long distances every weekend when I was in the Air Force, it had brilliant roadholding for a bike of that era and never let me down, not that much to go wrong with a two stroke.

Dave W

[MuzzerParticipant @muzzer]

Posted by Neil Wyatt on 08/11/2018 17:18:43:

I like the idea of rattle harmonic balancers.

They could fit them to Mondeos and you wouldn't have to wait 60,000 miles before they sound like a bag of spanners.

:-0

N.

Haha, yes, I heard that the Mundano DMF is prone to premature failure!

It's not an inherent problem with DMFs so much as the supplier / engineers who cocked up specifying / validating them. I recall spending hours with an Indian customer who was very wary of them on account of a bad experience with them, as if they were somehow beyond being properly designed but most diesels have them these days and there are many examples that are trouble free. They give the effect of a massive flywheel with much reduced moment of inertia.

Murray

[GoCreateParticipant @gocreate]

I have a futrure project that requires spiral milling so today I have been busy converting a Drummond lathe head stock into a spiral milling attachment for my mill.

The first photo shows the head stock straight from the lathe. I stripped it down and machines the pulley casting, (which includes a gear for the back gear) then shrunk fitted and aluminium sleeve. The Aluminium sleeve was turned and milled to take a T5 timing belt, see second photo.

The plan is to use timing belts to get a drive from the mill lead screw. I think using the Drummond lathe head stock has benefits in that I can drive it in its high gear or in back gear. In backgear it gives me a 9:1 reduction not an ideal figure. The first job will require a 10:1 , so will use the back gear and have a small reduction from the lead screw using toothed belts.

The last photo shows the Drummond head stock converted, now I need to arrange for an intermediate shaft between the mill lead screw and the Drummond lathe head stock, that's tomorrows job, details to follow.

Nigel

[Joseph Noci 1Participant @josephnoci1]

Some more experiments with the Rattle Dampers..

Paul White asked some difficult questions – How to base a 'rattle' damper design on mathematical foundation, so that led to a whole divergent exercise, one which I am happy to say, I simply gave up on! I managed to develop a convincing mathematical model of the stepper motor, and the toothed belt compliance , but a model of the rotary table, worm gear, and friction assumptions became awkward, And then trying to derive a model for variance in stepper torque related to table friction versus stepper mechanical position against the torque vector….

It was easier to make a half dozen variations of the rattle damper and test them!!

What I found- ( slugs always 10mm diameter, 18mm long)

1). Keeping the slug size constant and increasing the diameter of the slug hole in the flywheel from 11mm to 14mm reduced hugely the tendency for step-loss at low RPM ( sub 30 rpm), but adversely affected the ability to avoid stall at high RPM.

2). Increasing the diameter of the the flywheel in 1) above, to keep its weight the same as a flywheel with non-increased slug-holes had no obvious positive or negative effect. The increase was done by simply adding a sleeve of material over the outer of the flywheel.

3) A flywheel of 60mm diameter, with 6 slug holes of 11mm, centered on a 22.5mm radius was the benchmark and worked well, as previously described. Bringing the slug holes closer to the center, on a radius of 15mm, resulted in the high speed end being unaffected ( worked well), but the low speed end was almost as bad as with no damper fitted.

4) A 50mm diameter wheel was made, with 11mm slug holes on a 17mm radius was made. The slugs were 10mm diameter x 18mm. made in lead. This wheel performed VERY well, both at low rpm and high rpm. However, after a 15 minute cycle running from 0 rpm to 100rpm and back, each cycle taking 30 seconds, the lead slug had reduced to 9.8mm diameter (approx..) and the length had increased to almost touch the sides of the covered hole.

Obviously the slugs are being hammered! Just shows the amount of harmonic vibration in the stepper cycle. A huge advantage of the lead slug – dead quiet! No rattle at all. However, the slug would most likely need to be encased in a thin walled steel tube to prevent slug deformation – Although I suspect that thin tube would wear through fast..

To see the wear effects, I ran the 60mm benchmark flywheel with steel slugs for 60 minutes, 30 sec ramp up, 30 sec ramp down, with a 15 sec dwell at 1000 rpm. On completion I removed the aluminium side cover ( keeping the slugs in place) and each cavity was black; a microscopically fine black powder covering the entire hole and slug. Collecting all the powder in one hole amounted to maybe a 1/4 of a match head worth..

This implies a high wear rate, although I guess this would be of little consequence in our workshops where the use is infrequent and of low period..

I will most likely go for a lead filled tube slug, and the smaller diameter wheel – it is easier to get a belt cover over it all in my setup

Murray, you are on the right rack – The slugs appear to form a pendulum damper, being located in the centred position ( of the outer periphery of the hole) by centrifugal force, although this only applies to the medium, upper and higher speeds – at low speeds the slugs just seem to bang from side to side, and I suspect their benefit comes mainly from an almost random perturbation of the stepper resonance, in effect breaking up the resonance.

Such a simple device, with some amazing benefits, but its simplicity certainly belies the underlying complexity!

And I was just doing some software for a gear hobber for some friends…

Joe

[Ian PParticipant @ianp]

Joe, what an interesting description of your trials and results, I'm trying to get my head round it all but I am impressed with how well you have got it to work. I suspect getting the materials and dimensions right for a perfect answer would take a long time.

The energy to wear away the slugs or change their shapes must come from somewhere so theoretically introduces a loss of power, not that it matters if it does the job. I wonder whether the wear occurs mostly because the slug is rotating (relative to its pocket) its being forced into changing direction rather than just a straight hammering.

Great work, more power to your elbow

Ian

[Trevor Crossman 1Participant @trevorcrossman1]

Joe, your interesting exercise reminds me of long past times flying in Blackburn Beverleys and watching the numerous harmonic dampers, which consisted of a pair of heavy cylindrical weights with bonded rubber cores mounted on a shaft within open boxes fixed to the fuselage frames, all oscillating merrily and absorbing some of the vibration. Radial engines have harmonic dampers fitted into the crankweb, though how the design engineers arrive at the right mass and positioning is beyond my grasp of mathematics! You might find this article interesting___http://www.enginehistory.org/NoShortDays/TV.pdf

Trevor

[DrDaveParticipant @drdave]

After months of procrastination, I finally bought a 32mm hole cutter and made the holes for my milling chucks. Appologies for the photo being the wrong way…

Now, what can I get to fill the vacant holes?

[EmgeeParticipant @emgee]

Hi DrDave

You could fill 1 with a tapping head, maybe a Tapmatic 30 size.

Emgee

BTW the control panel has a new life !!!!!!

[Cornish JackParticipant @cornishjack]

Trevor Crossman1 – Bevs – when and where?? Self, 58 – 61, 'Dirty 30' at Dishforth and 53 at Abingdon. PM if appropriate.

rgds

Bill

[Joseph Noci 1Participant @josephnoci1]

Posted by Trevor Crossman 1 on 09/11/2018 22:11:49:

Joe, your interesting exercise reminds me of long past times flying in Blackburn Beverleys and watching the numerous harmonic dampers, which consisted of a pair of heavy cylindrical weights with bonded rubber cores mounted on a shaft within open boxes fixed to the fuselage frames, all oscillating merrily and absorbing some of the vibration. Radial engines have harmonic dampers fitted into the crankweb, though how the design engineers arrive at the right mass and positioning is beyond my grasp of mathematics! You might find this article interesting___http://www.enginehistory.org/NoShortDays/TV.pdf

Trevor

Trevor, that is a very interesting link! Fascinates me how the Math of 50 years ago, even centuries ago, remain a constant. Many advances in many fields of engineering and technology in the last 40 years, but the basic Math simply endures, refined maybe, but unchanged!

Joe

[John MCParticipant @johnmc39344]

Posted by alan lloyd 3 on 09/11/2018 18:45:58:

John mc, are those Ariel Arrow/Leader cylinders?

It certainly is, the "rebuilt" engine spat out a gudgeon pin circlip damaging a cylinder, hence the need for a rebore.

Is that a 900SS? Just put mine away fro the winter.

John

[DrDaveParticipant @drdave]

Posted by Emgee on 09/11/2018 22:50:53:

BTW the control panel has a new life !!!!!!

Pleased to heard it, Emgee. They are impressive machines for their size.

DrDave

[Danny M2ZParticipant @dannym2z]

Today I repaired a Mills Mk1 1.3 model diesel engine that I picked up for $20 at the recent Aussie Nationals.

It ran quite well until I made a spinner nut with a tight thread that sheared off the cheesy crankshaft. It is threaded 3/16" Whitworth.

To make a new shaft is another day so decided to tap the broken shaft for a stud or screw and picked 4-40 as I have plenty of shcs in this size plus taps and dies. (3mm was the other option)

First problem, how to hold the shaft so made a collet from a scrap of aluminium alloy with a diagonal slit, it worked OK but required lots of tightening of the 4 jaw chuck – next time it will just be in 2 halves.

Once centered it was easy to drill and tap the shaft so decided to make a prop drive washer to fit over the pesky pins that were fashionable in 1947 but ruin a good propeller.

In the end it all worked out so test run in a few days when the neighbours are at work.

* Danny M *

[Mark RandParticipant @markrand96270]

3/16 Whitworth is one of those threads (like the US 10-24 threads) that is really too coarse for its diameter. If it's made in a hardened shaft it's ok. If it's soft, the small core diameter isn't really strong enough.

DAMHIKT!

[Ian S CParticipant @iansc]

With your collet, whether cut from square as you have, or from round as I do, after cutting through the side continue about half way through the other side, things get a bit more flexible, not so much heaving on the chuck key.

Ian S C

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Mark Rand on 10/11/2018 10:51:45:

3/16 Whitworth is one of those threads (like the US 10-24 threads) that is really too coarse for its diameter.

.

… a fact recognised by the British Association for the Advancement of Science.

MichaelG.

[SamsarandaParticipant @samsaranda]

I seem to remember that Renault formula 1 cars were fitted with some form of inertia/harmonic damper to their chassis, a few years ago but it was outlawed by the FIA because it gave them an advantage over every other team because none of them had thought about the idea themselves.

Dave W

[John MCParticipant @johnmc39344]

Dave W, could that have been an "inerter damper"? That was McLaren F1 who tried it, they called it a "J" damper. I believe there work was based on something Oxford uni came up with.

I did some work on an inerter damper before I decided to stop working for a living, must ask if the how its going.

John

[Les Jones 1Participant @lesjones1]

Screwcut a coarse thread (About 40mm pitch) on wood.

It did require a modified changewheel setup.

The gear ratio was too high to drive it from the spindle so I had to fit a handle to the input of the gearbox that drives the leadscrew,

Les.

[Jon LawesParticipant @jonlawes51698]

I was involve in some of the trials work for the Harmonic dampers fitted to the Seaking rotorhead. Thats some big dampers!

[alan-lloydParticipant @alan-lloyd]

John mc, yes it is a 900ss, it should be black and gold, but I liked the silver/ blue, not right for the year but so what, I don't have it now as I swapped it for a Harley 45

[Ian Skeldon 2Participant @ianskeldon2]

Les Jones 1, is that a Chester 9 x 20 Lathe? No real reason for asking, I am just curios.

[SamsarandaParticipant @samsaranda]

John MC, thanks for the correction, memory not as good as it used to be, I remember it was a formula 1 team but confused with which one, I remember the other teams all complained of unfair advantage so FIA banned it to keep the peace.

Dave W

[Les Jones 1Participant @lesjones1]

Hi Ian,
It;s a Chester DB-10G wich I susspect is based on the 9 x 20. It has had quite a few modifications made to it.

Les.

[Danny M2ZParticipant @dannym2z]

Posted by Ian S C on 10/11/2018 11:31:28:

With your collet, whether cut from square as you have, or from round as I do, after cutting through the side continue about half way through the other side, things get a bit more flexible, not so much heaving on the chuck key.

Ian S C

Thanks Ian. You way seems a bit easier than my 'Plan B' which was to drill the block for locating pins and split the thing in half. As it was a one-off job nothing lost and a lesson learned.

The reason for the square collet is simply that I had an off-cut that exceeded the diameter of the crank-web and was of perfect length for the job. With a 4 jaw chuck I thought 'well, why not?'

My biggest mistake was to break the crankshaft in the first place!

* Danny M *

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