Author Topic: Freelance mill engine from Stuart castings.  (Read 32820 times)

Offline Gas_mantle

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Re: Freelance mill engine from Stuart castings.
« Reply #60 on: December 28, 2017, 02:18:04 AM »
Looking good, the bearings turned out rather nice  :)

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #61 on: December 28, 2017, 03:39:57 AM »
Hi Chris , here is a drawing of the innards of the bearing but it is not as clear as it could be... i do have another pic somewhere that shows the tapered parts more clearly.these ones may be based on the cam principal which is why the bolts are in slots ?!!

Willy

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #62 on: December 28, 2017, 06:23:54 PM »
HI, Here are more drawings of what is going on inside those bearing blocks.........Some clever stuff going on there but quite difficult to model in our sizes !!!!

Offline crueby

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Re: Freelance mill engine from Stuart castings.
« Reply #63 on: December 28, 2017, 06:35:08 PM »
Oh, now that is quite clever!!  Thanks for the extra details!

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #64 on: December 28, 2017, 06:55:32 PM »
And some pics of real engines........with quite elaborate lube boxes !!

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #65 on: December 31, 2017, 01:22:31 PM »
The works so far......I have sort of put the 3 bearing blocks in place and will finish profiling them at a later stage. I now need to make the con rod so am looking at various prototypes to copy! also the allen valve gear needs to be designed so still pursuing that....

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #66 on: January 01, 2018, 02:19:29 AM »
I have been looking at lots of valve motion angles for forward/reverse engines and there is quite a variation  between 30 Degrees and  3 degrees past 90.  Anyway i have decided on 12 degrees and see what happens....I have turned up a piece of perspex with the angles marked out and will use this as a template when milling the slots in the crankshaft.

Offline crueby

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Re: Freelance mill engine from Stuart castings.
« Reply #67 on: January 01, 2018, 02:23:35 AM »
The slots you mention are for keys to the eccentrics?

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #68 on: January 01, 2018, 03:50:59 PM »
Hi Chris ,yes i have decided to do it this way but there is a lot of compromises to contend with  Lap/Lead/angle of obliquity to name just a few !!! I have been trying to decipher this book on valves but it is full of compromises !

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #69 on: January 02, 2018, 12:14:47 AM »
The slots have been milled out using the perspex template and the crankshaft loctited  into place again using the perspex to sight through to the web....I will leave this till tomorrow to set ..

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #70 on: January 03, 2018, 01:20:13 AM »
The crankshaft is now pinned to the webs and the central part sawn off, then filed to shape. the engine has now been transferred to a piece of perspex.....

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #71 on: January 04, 2018, 01:26:28 AM »
I have now made a mock up of the eccentrics and sheaves from SRBP and perspex. I have made the eccentric offset 5/32" however when i measured the travel with them in position it was  .274" rather than 5/16"  >3125"  ie twice 5/32" so is this normal  ? or is it  because i measured it wrong ??!! The keyways were cut out with the broach and the keys were filed up from rod...

Offline crueby

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Re: Freelance mill engine from Stuart castings.
« Reply #72 on: January 04, 2018, 02:28:55 AM »
Something wasn't centered or slipped if it came out less like that. One easy way to goof is if you don't have both axises (axes? Directions!) properly centered on the mill and move over one axis by the offset, it will wind up short. Good that it just the mockup!

Offline steam guy willy

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Re: Freelance mill engine from Stuart castings.
« Reply #73 on: January 04, 2018, 11:08:08 PM »
Hi Chris, yes i think the drilling was not quite accurate enough  however it was only 18 Thou..!! I have also gone back to basics and have measured the actual valve travel required. I made a temporary valve from perspex and calculated the travel required by visual means . this travel is different from the ST drawing, but it does suggest that one should adjust it from the actual port dimensions. However in mid gear there is no movement of the valves, making the offset greater then will allow ample movement of the motion by the lever for the full forward and backward direction to take place. The slots will then be filed into the quadrant to achieve full power once the engine is tested....The Allen valve gear will be designed next using the hints and tips in the valve design book.....

Offline crueby

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Re: Freelance mill engine from Stuart castings.
« Reply #74 on: January 05, 2018, 01:30:06 AM »
What is the 'Allen' valve gear? There are so many variations its hard to keep track. Do you have a picture of it from one of the books?

 :popcorn: