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Another Paddleducks build log
spuddevans:
--- Quote from: NickG on August 24, 2009, 04:45:34 PM ---Presume the crank journals set 90 degrees apart on this engine? Do you have a method of achieving this or just by eye?
Nick
--- End quote ---
Hi Nick, yes, as I understand it ( and that is quite a statement :lol: ) the cranks are set at 90degrees. I think that it is set by trial and error ( in my case, probably more error than trial :bang: ) I could be in error in saying that, I have read through the plans a few times but I have the memory of a fish.
I got a bit more done today, worked on the flywheel recess.
I started off by re mounting the flywheel in the 3jaw, I wasnt too worried about it being precisely concentric. I ground up a new Hss blank to do the job and then had at it.
I then changed tools to a 6mm round profile and put a little radius to take the sharp edges off.
Then I had to tackle putting the 3 holes in the flywheel. This meant breaking out the rotary table. I now have yet another item on my "To Make" list, as I need a means to attach my 3jaw self-centering chuck to the rotary table. But until then I have to make do with a slightly more convoluted means of attaching items to it.
So then, how does one secure a round item, ie my flywheel, to the Ro-Tab and get it centred up?
Well this is how I did it, there's probably many other ways, and maybe easier ones too :lol:
I eyeballed the flywheel into the center and attached with 2 clamps, but only tightened them thumb tight. Then mount a Dti on a mag base mounted on the table, with the finger set against the inside of the 5mm mounting hole. Then just rotate the table and "bump" the flywheel ( or whatever you are centering ) until the Dti reads the same all the way round the flywheel, or within reason ( I haven't finished the outer edge of the flywheel yet, so it still has some marks which bounced the Dti needle a bit, but I just got the reading at an average all the way round it )
Then drilled the three 4mm holes at 120degrees spacing.
Then I drilled and tapped m3 for the securing screw.
And this is the resulting flywheel,
That's all I got done today.
Tim
bogstandard:
Tim,
I don't think there is anything in the writeup about how to get the cranks at 90 degs to each other.
But it is easy enough to do by setting one vertical and lining up the other by eyeball against say the edge of the baseplate. As long as it is near enough, the engine will run perfectly. They could be up to about 5 degs out either way, and it would still run OK.
The secret is to tighten up all the crankwebs and pins except for one at the centre bearing position, then once that is in position, tweak it up and everything should be in line. The critical bit is the 90 degree lead on the eccentrics for the timing, and if you took my advice and marked a line on the eccentric, that makes it much easier. Each end is timed individually, to the crank nearest the steam chest, that is why the crank position isn't so critical. That is ok for a piston valve engine, but not for a slide valve twin.
Hope that hasn't confused too much.
John
spuddevans:
--- Quote from: bogstandard on August 25, 2009, 02:37:06 PM ---I don't think there is anything in the writeup about how to get the cranks at 90 degs to each other.
--- End quote ---
Well that would be why I cant remember reading it then :lol:
--- Quote ---But it is easy enough to do by setting one vertical and lining up the other by eyeball against say the edge of the baseplate. As long as it is near enough, the engine will run perfectly. They could be up to about 5 degs out either way, and it would still run OK.
The secret is to tighten up all the crankwebs and pins except for one at the centre bearing position, then once that is in position, tweak it up and everything should be in line.
--- End quote ---
That sounds like a good plan to follow, thanks :thumbup:
--- Quote ---The critical bit is the 90 degree lead on the eccentrics for the timing, and if you took my advice and marked a line on the eccentric, that makes it much easier. Each end is timed individually, to the crank nearest the steam chest, that is why the crank position isn't so critical. That is ok for a piston valve engine, but not for a slide valve twin.
--- End quote ---
I havent made the eccentrics yet, but when I do I will make sure to mark a line as the plans call for :thumbup:
--- Quote ---Hope that hasn't confused too much.
--- End quote ---
No, that has cleared things up quite nicely.
I just have to say that I really appreciate your advice and helping me out, it is good enough of you to have taken the time to write the plans in such a clear and easily-followable format and make it freely available to all, but you go beyond the call and carry on giving advice and tips to help others out. I really really appreciate that :thumbup:
Thanks again,
Tim
spuddevans:
Got a bit more done, started work on the crankshaft rods, I only had 5mm stainless ( got some 4mm stainless rod on the way ) so I just cut the 3 lengths of the 5mm, sized them on the lathe and then polished them while still on the lathe with some wet-n-dry.
Then I set up the spin indexer on the mill and milled the 2 flats on the longer 5mm rod, and then the flat on the other one.
Then I moved on to the eccentrics, I grabbed some steel and chucked it on the lathe. Turned it down to 18mm and installed the 4mm groove's on each eccentric.
The next step will be drilling the offset hole and then drilling and tapping for the fixing screw.
Tim
edit: If anyone wants to see larger versions of the pictures click Here
spuddevans:
Got a bit more done today, got some 4mm stainless rod so I cut off 2 pieces for the big end pins.
Then I turned to the eccentrics, and the slight problem as how to hold them in order to drill the offset hole in both of them. It occured to me to try clamping my little 3 jaw self-centering chuck directly onto the mill table, and what do you know, it worked!!
Then after drilling both, it was back over to the lathe to re-mount them using a 5mm rod that was tapped M3 and a M3 screw.
After a little turning
One lesson I have learned is to keep your mouth in the closed condition when turning steel (or other metals too), if you think the little chips are a bit hot on your bare arms, wait til you get one shoot into your mouth :bugeye:
Anyway, after that I drilled and tapped the fixing holes, then I discovered that I dont have any M3 grub screws left, so at the moment the eccentrics are fixed by faith. Being the excitable type I quickly assembled the bottom plate, bearing blocks with ball races, crank assembly (in my hurry I mounted one of the crank webs the opposite way round to the others, it doesnt make a real differance I think, but it looks a bit odd) and flywheel and eccentrics.
Whoo hoo!! It's starting to look more like an engine and less like a collection of parts :headbang:
Next will be the support posts I think :scratch:
Tim
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