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| Spurry:
Peter I am taking a particular interest in your build as I have the castings for the same build. Is it an optical delusion or are the PCD's of the holes on the cylinder ends at a different pitch? The plan shows the cylinder ends at 1 3/4" diameter, but my casting is not completely cleaned up and it's less than that already. I will have to stick a piece onto one of the feet as the caster must have had a new belt on his sander and been a little too enthusiastic. I have made an excel speadsheet whereby you enter the fractions in one column and metric dimensions are churned out in another. This sheet is then kept with the drawings for constant referral. :) Pete |
| klank:
Thanks Stew, Benni and Rob - I appreciate the encouragement. Pete - yup, you spotted my unfortunate error. The casting as provided had a rough bore, a little out of true with the shoulders of the casting - particularly so at the "outboard" end. It was only after finishing the bore as shown that this became more evident. I should have originally set up to bore the casting, based on the casting's shoulders as a sort of datum, rather than taking the centre(ish) of the wood filled original bore. After completing the cylinder bore, I machined the outboard end shoulder at the same setting as for the bore itself, to get it to look better - but the outer shoulder diameter, once round and true had reduced by a couple of mm. from what it should have been. I made the outer cover to fit, but had to reduce the PCD for the bolt holes accordingly. So, yes, one end cover is slightly smaller than the other, with a reduced PCD. A mistake I have learned from for the future. This error in original setting up was pointed out to me by a friend - but I didn't really understand what was meant at the time. There is an article in the recent ME about doing this sort of det up properly properly, by Dave Clarke - when he machined the cylinder casting for a "Monarch" engine. I wish I had read that in time and understood that the way I went about it was wrong! As a legacy of reducing the PCD - I may have a latent problem now in steam leakage around one of the securing studs being too close to the steam "pocket" edge. I shall possibly have to deal with that later! Anyway - I do hope my mistakes may help you avoid doing the wrong set up. Best wishes Peter |
| Spurry:
--- Quote from: klank on May 30, 2011, 01:20:51 PM ---Anyway - I do hope my mistakes may help you avoid doing the wrong set up. --- End quote --- Peter Thanks for sharing the info. I do have to learn from the mistakes of others, as I do not have enough time left to learn from just my own. :thumbup: Pete |
| klank:
Just a few bits to add - its been very very hot in the garage/workshop - we're in a bit of a drought down here. The piston rod crosshead is machined out of a piece of 1/2" sq. bar :- Machining is quite straightforward - ends up like this :- I should add that the "rounded" inner face of the fork needs to be fully "squared off" afterwards - or the little end of the piston rod will not fit properly. The slide bars are machined from two pairs of castings - two each of tops and bottoms - bolted together, but held apart by 1/8" brass spacers. The main points to watch are that the slide faces, both in the vertical and horizontal plane are truly at right angles and that the lower horizontal face of each is exactly the same and at centre height of the cylinder, less half the thickness of the crosshead slipper. I machined the lower slidebars together in the milling vice, using parallels and a spacer between them. :- The slippers are againg machined from the remaining (supplied) 1/2" square bar stock. They are, I suppose, like a pair of thin T nuts, with a blind hole inset in the base part. To ensure concentricity, I marked out the centre point of the hole using an optical centre pop, but then, having set the work up in the milling vice, cross checked using a laser edge/centre finder in the drill chuck and finding centre by dial reading from the edges. You can just make out the laser dot on the right hand slipper :- The hole, according to the plan is supposed to be "reamed" 3/16" to a depth of 4mm! I used a 3/16" drill after pilot drilling and finished with a "D" bit. I then tried a "dry run" to fit some components together prior to final marking out for drilling/tapping the baseplate. :- At last its starting to look like an engine! Best wishes Peter |
| klank:
Its taken a little while to pluck up courage to write this next chapter, but a good friend suggested I should, in order that it MIGHT prevent other beginners from making the (potentially very) harmful mistake(s) I have recently achieved. For those more experienced builders who may read this - look kindly upon me please - I made a complete male chicken of the flywheel and nearly killed myself! Here goes. Having seen all of the recent really beautiful engines being built, I decided that before I carried on with the build, I should make the finish on my flywheel look a bit more professional. It will be painted later, but compared to other engines on display, I could do a lot better. It ran quite true - no sign of wobble, but the surface finish on the shoulders of the rim and spoke web was poor. Probably as a result of tool chatter and not using HSS tooling (I don't want to get into the argument of tipped vs. HSS tooling here). Anyway, I set up the flywheel again in my 5" four jaw with the jaws reversed, clocked it true to the outer rim and tried to gently skim the offending area on the side of the rim first. The flywheel is approx. 6" dia, and the chuck scrolls were not on their limits. However, I put some "squashy" plastic card packing under each jaw to prevent marking the rim. I was using a right hand tool, bringing it towards me across the rim shoulder with very light cuts only at about 350 rpm. A nice hissing noise, with fine dust being produced. I got to the end of the final cut, and just as the tool met the corner of the edge of the shoulder/rim face, I became aware of something coming rapidly at my face. Now I do wear protective kit :- safety 'specs, a heavy leather chest apron and a hide gauntlet on my left hand (hot swarf protection). I moved my head to the right without thinking and the flywheel, spinning like a gyroscope, struck me on the left side of my chin, ran down the side of my throat, bounced off my collar bone and landed, spinning, on my left foot! At the time there was no pain. I picked it up - no obvious damage, and decided to go indoors and get a cuppa tea. My wife asked about "all of that blood on your neck!" and realized then that the rim corner - as sharp as a scalpel, had left a fine cut all down my neck. Just a fraction deeper - is that where my jugular is? Anyway - my completely stupid errors - learned a lot from this! :- I should have used copper or thin aluminium packing (drinks' can or some such) under the jaws. The tool should have been going away from me. I should have brought up the tailstock with a centre in it, against the hub of the wheel. I guess I was lucky (this time!. Yes - I should have done it better - but I did not realise the potential for injury/damage with the wrong set up! Anyway, I re-machined the rim shoulders again on each side (doing it the correct way and with better non-slip packing), and realised that overall, the thickness of the 'wheel was a little less than it should be. As a "sop" to my stupidity, and to give the engine a bit more texture (and try and replace some of the missing inertia of a fatter 'wheel) - I sourced a small cast iron flywheel from RDG Tools (usual disclaimer). They are selling off some surplus Stuart cast iron 'wheels of various sizes at quite attractive pricing. I machined this to resemble a grooved pulley wheel to drive steel ropework, and mounted it on the overhang of the crankshaft with a key. Not my idea I must hasten to add - I have seen other competed Tina engines with this "extra" - but it does add a bit more to the overall look of the thing I think. :- A sobering episode! |
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