Author Topic: Coles C-611  (Read 4667 times)

Offline Laurentic

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Re: Coles C-611
« Reply #105 on: June 09, 2021, 10:45:29 PM »
Can you not just chuck him another Snickers ice cream to keep him quiet Jo, to pacify him a bit, after all, anything for a quiet life? 

Online crueby

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Re: Coles C-611
« Reply #106 on: June 09, 2021, 10:51:59 PM »
Can you not just chuck him another Snickers ice cream to keep him quiet Jo, to pacify him a bit, after all, anything for a quiet life?
Hmmm, mold some chocolate ice cream in the shape of a flywheel or cylinder to make him think its a bronze casting? Though he will scream when it melts!

Offline Jo

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Re: Coles C-611
« Reply #107 on: June 11, 2021, 09:54:23 AM »
I have found a way to keep him quiet so lets get on with the engine. I mentioned doing some measuring this is it:



What I am doing is measuring the height to the top of the piston rod. If I subtract half the diameter of the piston rod from this dimension I will get to the ideal height for the centre of the crankshaft. Having mentioned that the odd mm up and down on a model is not a concern but on full size it would cause additional bearing wear  :-\ Measuring the height to the top of the soleplate where the bearings are going to mount and found there was about 3mm to come off but only 1mm to come off the surface under the cross head guide bars.

Moving over to the mill and making sure we centre on the piston rod to provide the centre for later machining:



I also checked the measurements to the bearing surfaces and there is a slight bias to one side but it is less than 0.5mm not a problem  :)

Time to mill the top surfaces:



I then drilled and tapped for the crankshaft. First I tested the alignment through the bearings with a straight rod:



I then mounted up the crankshaft in the same position and found it was a little sticky as it went round:



This tells me that the crankshaft has "moved" i.e. bent slightly. This is probably because during the machining the crankshaft warmed up and then cooled slightly bent (the crank webs would have acted as a bigger cooling surface on one side and hence it cooled faster on that side  :Doh: ) I will sort that later.

In the meantime I am tackling the cross head design - you may note that I have not yet drilled the mounting holes for the slide bars as this is all part of the design problem that needs solving.

I have two cross head castings (so I have a second chance if I go wrong) and one piston rod and as you know no drawings  :ShakeHead:



and using my 3D CAD package I have started looking at the problem. The photo implies one slide bar but that means that the small end pivot will be very short and cannot be removed without unbolting the slide bars so I am first looking at two bars:



As you can see the pair of slide bars at 8mm wide does not leave much in the middle.... This is work in progress in the mean time I have a Qigong Class  :cartwheel:

Jo


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Offline Bluechip

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Re: Coles C-611
« Reply #108 on: June 11, 2021, 11:14:23 AM »

Offline Jo

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Re: Coles C-611
« Reply #109 on: June 11, 2021, 01:38:33 PM »
I still think the original design had a single bar on the side so this is what I am going to attempt for the first try:



Either way the slide bars would be more appropriate at 6.35mm wide so I can now go ahead and drill/tap for the two bars on the soleplate  :)

Jo
Enjoyment is more important than achievement.

Offline Jasonb

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Re: Coles C-611
« Reply #110 on: June 11, 2021, 01:50:22 PM »
Looks like a single square bar to me too when you blow the photo up and quite substantial too. Would it be possible to thin the small end of the rod a little so you have a bit more pin in each side of the crosshead if you feel it's a bit short on housing length?

Single bar is probably a bit easier to set up too as you only need 4 supports and no spacers and the captive pin saves having to do something to stop it coming out :)