Author Topic: Atom Minor Mk III  (Read 18874 times)

Offline Jo

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Atom Minor Mk III
« on: July 30, 2017, 10:44:16 AM »
The Mk III Atom Minor was the last of a line of "Atom Minors" which evolved from a long series of experiments conducted by  :NotWorthy: Edgar Westbury. The original Minors were rather larger at 15cc but by the time of the Mk III the engine capacity had been reduced to 6cc. I was lucky enough to get my hands on Westbury's own engine for a fondle :embarassed: but had to give it back  :(



So a picture of a standard Mk III made from castings alongside the Master's own engine:



Some of you may be aware I am currently on "light duties" in the workshop and have been roughing out crankshafts  ;D It has been too tempting so I am going to work my way through this one  :naughty: It is a nice simple little engine, nothing difficult:



I have three castings in my set which originally was supplied as a set of five. While I have a think about those I have started roughing out the crankshaft. Thi has involved simply putting the centres in for the crank and crank pin. First step it to reduce the EN8 down to the 31.75mm for the end of the crank with its pin.

Jo

P.S. Hemmingway can provide you your own set if you feel the need:  http://www.hemingwaykits.com/acatalog/The_Atom_Minor_Mk_3___designed_by_E_T_Westbury.html
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Offline Stuart

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Re: Atom Minor Mk III
« Reply #1 on: July 30, 2017, 11:39:52 AM »
Nice start there Jo

Now take it easy or I will send matron mum round to keep you in like but maybe Eric would be just as good  :stir:
My aim is for a accurate part with a good finish

Offline Jasonb

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Re: Atom Minor Mk III
« Reply #2 on: July 30, 2017, 12:39:13 PM »
So Jo are you going to stick a flywheel on it like Westbury's so that you can run it up yourself without worrying about your digits or fit a prop and leave it sat on a shelf without christening it?

What are the missing castings - Timing bracket and carb?

J

Offline Jo

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Re: Atom Minor Mk III
« Reply #3 on: July 30, 2017, 12:57:25 PM »
Thanks Stuart

Now take it easy or I will send matron mum round to keep you in like but maybe Eric would be just as good  :stir:

I was, I was, I promise, I promise  ::) I was doing so well then I listened to "I'm sorry I haven't a clue"  :facepalm: now I need to have another lay down .

JB: I have not decided on prop or flywheel. The missing castings are cylinder head and timing bracket. Cylinder head is easier from a it of bar stock and the timing bracket casting is not easy to hold.

Jo
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Offline Jasonb

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Re: Atom Minor Mk III
« Reply #4 on: July 30, 2017, 01:14:44 PM »
Have a lay down and watch the live F1, Oh no you can't can you  :LittleDevil:

Maybe once you get the big hole through the bracket it can be stuck to a bit of rod and held in a collet block so you can machine all the other bits then just heat it off the rod and slit the clamp.

Offline Jo

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Re: Atom Minor Mk III
« Reply #5 on: July 30, 2017, 02:01:55 PM »
Have a lay down and watch the live F1, Oh no you can't can you  :LittleDevil:

I wouldn't want to use up a good workshop afternoon watching sport when I can watch it later and I have better things to spend £432 of my money on than wasting it so I can watch the other half of the races live.

Jo
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Offline Jo

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Re: Atom Minor Mk III
« Reply #6 on: July 30, 2017, 03:23:04 PM »
While some have nothing better to do then sitting around with their feet up drinking watching the goggle box, others of us have been busy making swarf  :pinkelephant:

Its a very thin crankshaft on this engine  :o Its been turned down to 6.35mm diameter, with the required small radi as it joins the main web. It was not possible to get rid of the sharp edge on the outside of the web with the drive dog in the way so the crank was mounted up in a collet and a file used to clean up the side nearest Mr Silky's nose.

Last bit for today was to mount the faceplate and play find my crankshaft turning jig that the Workshop Gnome had been looking after  >:( As I mentioned the crank is very thin and I had to turn the clamp over to be able to clamp it up to hold the crankshaft firmly. Then it is just a case of brining  up the centre and tightening up the jig on the faceplate.

So we are all ready to go for tomorrow  :cartwheel:

Jo
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Online Vixen

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Re: Atom Minor Mk III
« Reply #7 on: July 30, 2017, 08:34:25 PM »
Jo

Metal therapy is good for the mind and soul and is sure to speed the healing process. Go at it slow and gentle, just don't rush or strain yourself.

Nice little engine, but it must have a prop not a flywheel.

Are you sure you cannot make the Bristol Show at Thornbury next weekend? The offer of a lift home on Saturday evening is still open.

Cheers

Mike
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Sometimes, it can be a long and winding road

Offline Jo

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Re: Atom Minor Mk III
« Reply #8 on: July 31, 2017, 08:18:57 AM »
Are you sure you cannot make the Bristol Show at Thornbury next weekend? The offer of a lift home on Saturday evening is still open.

Sorry Mike, I have no way of getting there and I do not have the stamina to walk round yet  :( The advantage of my workshop is when I feel tired or any twinges I can go and lay down for an hour. All this having to go lay down I am still not cleared for any gardening  :wallbang:

I hope to get the green light to start trying driving again this week but it has been nearly 4 months. I am planning to start with a trip to the grocery store next week and maybe the following week try a longer trip and visit my Supplier (assuming he has some castings to tempt me with  ;) )

Jo
« Last Edit: July 31, 2017, 05:58:50 PM by Jo »
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Offline Jo

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Re: Atom Minor Mk III
« Reply #9 on: July 31, 2017, 11:11:11 AM »
I decided that I did not like the idea of turning the crank pin with a gap between the end of the crank and the turning jig so added a support and used to tailstock to push the crank face up tight against brass ring and the jig.

Then started to turn across the face down to the point that my tool holder hits the rotating centre. Then take this to depth taking slices off the face each time.


Hopefully my camera battery has now re-charged (and I have recovered from the tiredness  :-[ ) so time to make some more swarf  :)

Jo
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Offline Stuart

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Re: Atom Minor Mk III
« Reply #10 on: July 31, 2017, 12:38:16 PM »
Jo
You are an inspiration to us all getting up from your bed just to provide us with a new build to follow  :stir:

That will be a nice engine when finished

Take care and be safe
Stuart

Yes I remember Linda lacking any stamina, I had to do the ironing ,vacuuming etc.

But it was not up to her standards but it got us by
My aim is for a accurate part with a good finish

Offline Jasonb

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Re: Atom Minor Mk III
« Reply #11 on: July 31, 2017, 12:40:31 PM »
You will have it finished by Friday at this rate ;)

Is there any provision for getting oil to the front bearing ? seems a long way from the crankcase.

Also the sectioned assembly seems to show the end of the crankpin threaded to take a CSK screw but the drawing of the crank just shows an 1/8" hole?

I did find a photo of a full set of castings, the head is definately not great loss and probably easier starting with some solid bar.

J
« Last Edit: July 31, 2017, 12:44:27 PM by Jasonb »

Offline Admiral_dk

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Re: Atom Minor Mk III
« Reply #12 on: July 31, 2017, 12:56:38 PM »
Jason - regarding lubrication of the front bearing - crankcase presure will lube it, as long as it is lubed when you start it.

Nice to see you back in the shop Jo  :)

Offline Jasonb

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Re: Atom Minor Mk III
« Reply #13 on: July 31, 2017, 01:10:21 PM »
Jason - regarding lubrication of the front bearing - crankcase presure will lube it, as long as it is lubed when you start it.

Nice to see you back in the shop Jo  :)

I was just going by the fact you often see oil holes and grooves or a hole up the crankshaft to help get the lub upto the bearings on Westbury's designs but could not see anything on this one, particularly as it is rear induction.

Offline Jo

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Re: Atom Minor Mk III
« Reply #14 on: July 31, 2017, 05:30:28 PM »
Yes I remember Linda lacking any stamina, I had to do the ironing ,vacuuming etc.

But it was not up to her standards but it got us by

I am looking into the idea of buying myself a little robot vac, rather a robot dustpan and brush, to help with the cleaning  ;)

You will have it finished by Friday at this rate ;)

...

Also the sectioned assembly seems to show the end of the crankpin threaded to take a CSK screw but the drawing of the crank just shows an 1/8" hole?

I am in no rush: I won't have a full week this week as I have a day out at the Doctor's so she can inspect my bullet hole  ::)

That pin is a 3.18mm diameter and is riveted onto the rotary valve.

Nice to see you back in the shop Jo  :)

Thanks Per  ;D

Back to the swarf making:

A bit of undercutting then take the pin to diameter and finally ream the pin.

Mount in a 5C block, using the split in the collet as a guide for peeking through the crank hole while squaring the crank up. Centre the crank by using the outside of the block. Then it is a simple case of using a boring head to mill the two recesses.

Jo
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