Atom Minor Mk III

[Vixen]

You have gone a bit further than just roughing out that crankshaft.

Sounds like you are on the mend.

Mike

[Roger B]

Glad to see your health and another engine progressing well   

[Nick_G]

.
Have you chomped the collet with the cutter.? 



Or is it just a reflection.? 

Nick

[Jasonb]

Final thin shim of metal dropped off on the final cut

[Jo]

Thanks Guys, recovery is slower than I would have liked 

Have you chomped the collet with the cutter.? 

Yee of little faith  That's one of Mr Silky's collets - H would have been thrown out of the workshop by now if he had done such a thing.

I have the excuse for a bit of casting fondling to decide how to machine the crankcase  .

Jo

[Nick_G]

That's one of Mr Silky's collets -

Jo

.
Well you will insist on using 'disposable' import tooling. 

Nick 

[b.lindsey]

Very nice result Jo. Just don't push too hard or you may be on the sidelines for even longer.

Bill

[Jo]

I chose to mount the crankcase casting up in the four jaw but it might have been better to mount using the four mounting holes 

So with the crank end pointing forward the outer end was faced to an appropriate depth to make the raised bit of the casting central (once the other side was taken to width) and then bored to 32.5mm. A tight fitting mandrel was turned then the other side taken to width. I  chose to leave it there as I need to have a think about the vertical bore...

The rough bearing housing was easily mounted in a collet and the other end tapped central and supported while the pads for the bolts were turned flat. Then it was easy enough to turn the other end to depth and to fit in the crank casing. As everything is nice and true it can be bore, reamed (not actually required  ) and counter bored. I was pleased that the bore came out true.

Jo

[Jo]

It is important that the surface for the contact bracket is parallel to the bore so this is easily achieved by mounting the bearing housing on a piece of bar on the collet chuck. this allows it to be taken to length and for that important surface to be machined.

The resulting housing is a nice snug fit in the crank case but until the bearings are done no round and round testing can be carried out so I will have to go and make myself some fresh pizza. I love this having time to do some real cooking 

Jo

[bent]

Jo,

Never thought of turning the crank sides with a boring head, but duh, I'm new to this.  Do you just run the rpm's down low to keep the chatter and vibration down?

Fun to watch this build, maybe someday I will tackle an IC engine...

[Alan Haisley]

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

That's small enough to start by hand - or at least by "chicken stick".

[Jo]

Never thought of turning the crank sides with a boring head, but duh, I'm new to this.  Do you just run the rpm's down low to keep the chatter and vibration down?

The Boring head is run at a normal feed relative to the diameter it is turning so in this case about 400rpm 


To enable the required round and round testing a couple of bearings are required: In this case best pinky coloured Ph Br  Not that Mr Silky has any concerns about turning it 

The two bushes fit one in each end of the bearing housing and have been left at 6.2mm bore for now. I chose to secure them with 638 Loctite. Once secure they could be hand reamed from the inside out (at which point I remembered it was that Pinky Ph Br and have the blister to prove it    ) Which gives a crank that swirls nicely in its housing.

The next challenge is to work out how to hold the other cover 


I nearly forgot to mention the Doctor has given me the green light to start driving again  So best hide your castings   

Jo

[Vixen]

 

[Jo]

 

following extensive fondling I decided that the starting point for this casting was to true up the screw holes. Because of the carb lug it cannot be done on the lathe but needed to be done on the mill.

At this point I had to decide: make a jig or try holding on less than 3mm of material over those lugs  I chose to hold on the little bit of material and provide tailstock support. Because the casting was not held by much I took small cuts first turning up the part that fits into the crank case then the undercut which extends the casting out to where the rotary valve fits and finally taking as much off as I could while keeping that important tailstock support. I decided against parting it off  Instead gently hacksawed it off and took a final 0.1mm cut to finish the surface.

As part of the centre drilling I had remembered to put in the pilot hole for the 6BA tap  ;)Which just left a quick check it fitted the crank case before taking it out of the chuck and praying that the 6BA hole had come through in the centre 

Jo

[Stuart]

Well Jo you've not lost your touch at casting fondleling 

With regard to your post on the Stuart Williamson build that governed is just a twirly thing and does not operate

It's a nice model just done one

Filling in time at the moment before a long term build gets under way just waiting for the casting to be cast  so a 3inch weir boiler feed pump is on the bench


Stuart