CHUK, yes another one

[Jo]

In Graham's detailed build instructions he suggests two options for attaching the A frame to the base:

1, A pair of bolts from underneath going into the centre of the A of the frame so nothing shows. I was not convinced on having only two bolts holding the entire top of the engine in place   

2, Four bolts on the corners of the A frame but because of the positioning of the frame these will have to be inside the feet rather than outside. 

I opted for the four bolts and decided to drill through with the M5 tapping drill and thought to myself that's odd its sounds like there to be some sort of flashing on one side of the hole  then it did the same noise on all four holes.... When I took the casting down and turned it over it all became obvious  No one mentioned that the base casting had a reinforcing beam across it and the four holes lined up right on the ramp area of this 

I feel some studs coming on. Luckily I drilled the four holes 4.2mm for tapping an M5 tapping thread.

Jo

[Jo]

The bearing blocks came as two bronze castings, one of which looked like someone had been machining it  the other had a slight banana shape to it 

The only 'feature' on these is the boss so that is what is used to mount the block up in a four jaw to face the front and drill/ream the centre 6mm. Yes I know the crankshaft is bigger than 6mm but there is method in her madness... Machine the other the same. The reamed hole can be used to remount the casting in the four jaw chuck and we know the hole is central to the boss (now hidden behind the casting) so the next stage of boring will also line up with that boss. 

Boring through for the crankshaft and to fit the bearing: I have chosen to reduce the crankshaft to 3/8" diameter as I have masses of stainless steel that size (shafts out of old printers  ) and because the ball bearing is 4mm smaller on the outside than the bearing for a 10mm shaft. There is no dimensions on the works drawings for the depth of the bearing hole but we know the hole must be deeper than the bearing: this allows a gap behind the bearing so you can get a bearing puller in it if needed and prevents the centre from rubbing on the casting. The bearing was 7.1mm wide, I made the pocket 8mm deep.

We can now look to shape up the outside of the two blocks. They both must be the same height and ideally the same shape, so to do this I have joined them together using the bearing bores and mounted them back to back ready for the next bit of machining.

Jo

[Jo]

The bearing blocks have been cleaned up using the milling machine, the height being determined by the already machined block and I have found a feature   

There is no dimension for the crank centre height on the works drawings but we do know that the throw is 1" and the crank pin head is 10mm - This means that it needs 30.5mm over the top of the base to allow for the crankweb and pin. But we also have to take into account the small end there is no dimension on the drawings for this but on my CHUK2 I made it 19mm to allow me to fit a small bearing in it I also increased the throw to 28mm which would require 37.5mm over the top of the base. The actual measurement from the centre of the crank bearings to the top of the base is 32mm 

On the other side of the bearings is a groove in the side of the base to clear the flywheel. On the previous engine I achieved a flywheel diameter of 175mm. The distance from this centre line to the groove is 78mm, with the fillet on the casting its tight.  So I would prefer a bit more space there.

Maybe a packer would be a good idea but how thick and could I improve the lines of those blocks by adding it 

Jo

[Jasonb]

Packer would probably be better off added to the base and than blended into the existing fillet all hidden by paint. or you could scallop out some clearance for the crank rather than pack.

Boring and facing head would give the flywheel more clearance but I think I would be inclined to machine it all off and just have a flat side.

[Alyn Foundry]

Hi Jo.

What's the height from the top of the ( rough ) part of the base casting to the centre of the crankshaft please?  We have 35.5mm.

Cheers Graham.

[Alyn Foundry]

Sorry about the wonky picture, can't seem to rectify....

CHUK 1 Mk 2 with R.L.E. flywheel removed and Robinson replaced.

[Jasonb]

Looks like the one on the left of Jo's photo should have been extended rather than reducing the right hand one to match

[Alyn Foundry]

Hi Jo.

It would appear that I gave Colin a " used " Brass casting rather than two " new " ones, my apologies.

Luckily I have two remaining on stock, PM me your address and I'll get them in the post to you.

Kind regards, Graham.

[Jo]

What's the height from the top of the ( rough ) part of the base casting to the centre of the crankshaft please?  We have 35.5mm.

I have 32mm 

Jo

[Jasonb]

As bearings are being used is there a need for brass? bit of flat stock or plate would do or a couple of alloy home castings may even suffice for those that prefer castings

[Alyn Foundry]

'Twas just a " Bling " thing really Jason, many like the " exotic " look !! 

[Alyn Foundry]

What's the height from the top of the ( rough ) part of the base casting to the centre of the crankshaft please?  We have 35.5mm.

I have 32mm 

Jo

Hi Jo.

Three " extra " millimetres are in 2nd class post, they should reach you before the weekend. 

Cheers Graham.

[Jo]

The postman's days are numbered 

Jo

P.S. thanks Graham 

[Twizseven]

At least the original delivery man did not get blamed.

Colin

[Jo]

The flywheel as not as easy as it should have been 

There was lots of hard chilled flashing all over it which I had to resort to grinding off and the two halves of the pattern had slipped as can be seen from the turning pattern on the outside of the wheel and the sides were also chilled.

Fitting the wheel on the existing bearing stands the fit of the wheel in the groove can be considered  If it came up 3mm it might fit rather nicely in there 

While I pondered on the flywheel fit I decided to rough out the cam disc only to find it too was hard as  So it will join the crank and be taken out of some pieces of cast Iron bar.

Jo