Author Topic: 45CC Wall Wizard  (Read 13360 times)

Offline Jasonb

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Re: 45CC Wall Wizard
« Reply #105 on: September 18, 2018, 04:10:16 PM »
Don't tell the little fellow I have the castings for that Fairbanks on the front cover of his comic :-X

Offline Jasonb

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Re: 45CC Wall Wizard
« Reply #106 on: September 18, 2018, 05:13:29 PM »
I am hoping to do it using the dividing head: I can get 5 degrees by using an 18 hole wheel, then I just need to work out the offsets  :noidea:
Jo

Back to the cam, why do you need to workout offsets? it has flat flanks so you only need to know the base radius as that is the only height needed. If it had curved flanks and you were also machining a radius to the lobe then it would be worth doing by offsets but not for a simple profile like this.

I'd use the rotary table as you are going to want angles smaller than 5 degree intervals to get those tangental flanks in the right place.
« Last Edit: September 18, 2018, 05:19:16 PM by Jasonb »

Offline Jo

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Re: 45CC Wall Wizard
« Reply #107 on: September 18, 2018, 05:24:14 PM »
That was the problem it all seemed too simple... We had to check if I had missed something. The dividing head set up with a 18 hole wheel gives 0.5 degree increments  :).

Surus says best he does a quality check on your Fairbanks casting set just in case you are not looking after them to make sure they are not getting that pre aged patina that Graham specialises in  ::)

Jo
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Offline Jasonb

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Re: 45CC Wall Wizard
« Reply #108 on: September 18, 2018, 05:43:49 PM »
Not much point in working it out to 0.01 degrees then if you are only working to half a degree.

Offline Jo

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Re: 45CC Wall Wizard
« Reply #109 on: September 18, 2018, 06:39:09 PM »
The critical measurements are that one cam is machined round until 5 degrees either side of the datum and the other 10 degrees either side. Having first set the milling cutter to leave 11.8mm diameter on the root of the cam. 

Machining wise: do the shared face first and then the two outer ones and then remove the waste in what ever steps you fancy finishing with a file or as I will be some abrasive paper on a stick  :)

Jo
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Offline Jasonb

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Re: 45CC Wall Wizard
« Reply #110 on: September 18, 2018, 06:51:04 PM »
Not sure where you are getting your 5 and 10 degrees from, if you want to end up with the 1/8" and 1/16" widths shown on the drawings then the angles are nothing like that.

Also no shared face, draw it out in Alibre and you will see that.

Offline Jasonb

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Re: 45CC Wall Wizard
« Reply #111 on: September 18, 2018, 07:23:09 PM »
I would set it up at "zero and make the first cut down to the base radius as pic 1

Then rotate one turn of my handwheel and make another pass as pic 2

Then repeat until I get to 248.29deg. Pic 3

For the other lobe with the 1/16" dim start at 119.95deg and work round to 18.13 degrees

* just check the cams are the right phase I I did not bother with that just the 115Deg

Bit like this one except your can will be horizontal and cutter vertical

« Last Edit: September 18, 2018, 07:30:48 PM by Jasonb »

Offline Jo

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Re: 45CC Wall Wizard
« Reply #112 on: September 18, 2018, 07:23:27 PM »
 :headscratch:
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Offline Jasonb

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Re: 45CC Wall Wizard
« Reply #113 on: September 18, 2018, 07:37:56 PM »
Now try it with the correct base radius of 0.250" :insane:

Offline Jo

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Re: 45CC Wall Wizard
« Reply #114 on: September 18, 2018, 07:47:28 PM »
The base radi is not given   :disappointed:

Jo
« Last Edit: September 18, 2018, 07:56:35 PM by Jo »
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Offline Jasonb

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Re: 45CC Wall Wizard
« Reply #115 on: September 18, 2018, 07:58:51 PM »
Or it was missed off your later Coles drawing, it is shown on the original Wall Drawings as per my post above

Offline Jo

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Re: 45CC Wall Wizard
« Reply #116 on: September 27, 2018, 10:12:42 AM »
Mr Silky has taken the four cams down to the required 18.4mm and the exhaust have been marked in blue and the inlet red. At this point I realised I need to machine the opposite way to the drawing  :facepalm:

Mounting the cam blank in the dividing head the rough position of the tops of the cams were marked as a safety feature and I started doing the first cut. At this point I realised I had not checked that the worm would engage in the position that I had cut the flat :Doh: But luckily the last job I did used the worm and the 18 hole wheel so I got away with that one   :-X  As things were looking potentially a bit flexible I decided it was a good idea to add a machinist's jack under the cam while cutting.

The cutting chart has been put up on the white board for marking up  ;)

Before starting the second cut I checked the line of the cutter at the rear (why is it always the rear  :ShakeHead: ) of the work. At this point I felt a desire for strong coffee and a couple of Jaffa cakes before continuing  :paranoia:

Jo
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Offline Jo

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Re: 45CC Wall Wizard
« Reply #117 on: September 27, 2018, 11:55:06 AM »
Having machine the flats for the exhaust the inlet was tackled in the same way. Then the wanted parts of the lobes coloured to make sure I didn't over cut. I initially chose to cut flats but the last bit I used the handle on the indexer to free rotate the cam as it cut. I rounded one pair first then the second pair.

Checking against the drawing it looks like they are in the right position  :)

That wasn't as bad as I thought it was going to be :thinking:.

Jo
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Offline Roger B

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Re: 45CC Wall Wizard
« Reply #118 on: September 27, 2018, 12:12:17 PM »
Cams are fun  ::)  That looks good  :ThumbsUp:  :ThumbsUp:  :wine1:
Best regards

Roger

Offline Jo

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Re: 45CC Wall Wizard
« Reply #119 on: September 28, 2018, 04:09:08 PM »
Thanks Roger, yes they have lots of opportunities for adding unintended features on camshafts ::)

Having turned up the other end of the camshaft it was time to start looking at assembling it into the crankcase and checking the alignment of things. When I originally machined up the crankcase I noticed that one side of the case was thicker than the other and put it down to a slipped core - the crankshaft halves are symmetrical and on looking to fit the camshaft gear it is clear that one way round fits and the other doesn't.

The supplied Boston gear for the crankshaft originally had a 9.5mm bore and needed to be 12.7mm bore so it was bored out to fit the crank. When I came to the cam gear I noticed the hole in the gear is also 9.53mm but the drawing shows 7.94mm  :facepalm: just the sort of thing you need last thing on a Friday afternoon  :(

Enough joys for this stressful week of retirement. I have just presented Surus with a 500mm long 40mm diameter piece of EN8 and he has suggested that I should make us a nice meal then we could do a bit of casting fondling :wine1:

Jo
« Last Edit: September 28, 2018, 06:49:04 PM by Jo »
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