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xpylonracer

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Thanks for the pictures of all your kit. Far more than I need. I guess you have the test bars and gauges for calibrating them as well.
Cheers,
K2
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Hi Steamchick
I don't have any setting rings so have to rely on a mic to set the bore gauges.
I do have some gauge blocks, bought the imperial set from a firm closing down sale in the UK and the metric set from a Russian dealer when visiting Czechoslovakia in 1984 at we now call a car boot sale , it was at an airfield where I was competing in a model plane pylon racing contest, about 50 cars where goods were displayed. The exchange rate was excellent at that time and from memory I paid £15 for the metric set.

xpylonracer
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Imperial Slip Gauges.jpgMetric Slip Gauges.jpg
 

Steamchick

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Hi Xpylon, I guess you use the gauge blocks on your surface plate to set heights and set sine bars. If you have any ball or roller races in your spares bins, then you have some gauges... as these are ground to sub-thou tolerances. Easy to look up in the maker's table for bearing sizes. External mics should come with a gauge bar in the kit. But you can use your gauge sets. Internal mics need a gauge, or calibrated mic. ALL my second-hand mics were out of calibration... but make good consistent comparitors, so gauges are most useful. When I was a teenager in the machine shop I was taught to check the mic against the gauge (zero) every time I took it from the box for use. Also with every mic with interchangeable anvil it must be confirmed to the gauge after every anvil change. As I had small hands then, I had the smaller boring jobs as I could get my hands with internal mic down the bore. But even internal mics were always confirmed against external mics when close to finished size. And when possible, Go/No go gauges were used. Often these were made before boring commenced: 0.001" oversize, Size, 0.001", 0.002", 0.003" undersize in 1/2" sections on the end of a test bar - and with tapers and shoulders if appropriate.
For finish Honing, Brian describes a method that is good. Remember, honing is to improve the surface finish of a bore (by taking the peaks off the machinning marks), and eliminate tiny irregularities from the machined bore. It is not a recommended practice to remove quantities of metal if the bore is badly made. The hone will follow the "average axis" of the peaks, not the true axis from machining. So excessive honing can misalign or distort a bore (even microns will lead to excessive wear in use). Think of this... 0.001" ovality or taper from "bad" honing means you need 0.001" wear of high spots before you "run-in" the piston to get a good bore (circular and cylindrical). That is more than 1/3rd of the lifetime of most engines!
Cheers,
K2
 

ajoeiam

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Hi aj
Nothing wrong with Mitutoyo mics, silky smooth operating adjustment, as I said you are comparing the feel of a turned part and polished carbide mic anvils, all you can do is check at least once to be sure of the reading.
I also use dial calipers in bores, especially useful to check parallelism of the bore.

xpylonracer
wasn't trying to imply anything negative.
IMO there is even better than Mitutoyo and its that absolute top end Swiss tooling.
(Haven't run into others at that level but bet there would be a few more though.)
 

CFLBob

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I got a break between the other things I have to work on, so I got back to the cylinder using the method in that Abom79 video that ShopShoe posted. It dramatically improved my measurement repeatability. I even used my existing telescoping gauge for this, concentrating on the feel and tightening the barrel until it would hold the gauge until a light touch made it fall out of the mic.

Within the last couple of weeks, I had brought the cylinder to just under the 1.000 it's supposed to be. This time, in two sets of four measurements at both ends of the cylinder, my repeatability is .0001 to .0002".

The top (outer) end of the cylinder is 0.9962 and the measurement deep in the cylinder was 0.9976. Yesterday, I decided to press on and finished machining the outline of the cylinder, and cut it off to length. All that's left is eight holes to drill with four to tap. I'll do that using the mill as a precision drill press.

It's time to make the piston to match. First, with the cylinder off the lathe, I can look at some of the leveling questions and other things that have come up.

Footnote: chances are Florida is opposite from where you are if you work in the shop all winter. Around here, I work in the shop all summer to stay out of the sun. If I have anything that needs to be done to the house, the first question is "can it wait til winter?" As a result, every year I have a backlog of projects that start with "when it cools off, I need to..." I was doing the biggest project from about New Year's Eve until Tuesday, and now have just a couple left. One will be "a couple" of days and the other one day.
 

CFLBob

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It's time to declare the piston is ready to be put aside so that I can get the piston and conn rod ready for their role in this.

Rdy2PutAside2B.jpg


The inside of the cylinder hasn't been lapped, and I'm pretty sure that's something I should do. That will open the cylinder up a little, so it's probably best to do that first, although it can always be used to open it up some more.

One of the things I wanted to do was to verify the numbers for inside diameter that I talked about in the last post. It took me a long time to get numbers I was comfortable with and I wanted to cross check on the completed cylinder. With the cylinder parted off the blank, I get the big advantage that I can now use the telescopic gauge exactly the same way on both ends because I don't have to work from just the one end. Now I can just turn the cylinder around and test from either end.

The numbers I got testing today matched the previous numbers.

I found earlier this week that while I thought I'd ordered the #5-40 screws that hold the head onto the cylinder, I actually hadn't. I need to order some hardware and the piston ring this engine specifies (a Vyton polymer ring).
 

Steamchick

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Hi Bob,
Just going back a bit, to clarify some odd points:
  • Post #126. I had a small boring bar much like this, but it wasn't good for the smallest bore, as the bottom corner of the tool bit was touching the bore before the proper top cutting edge. So I made my own stuff so I could grind away the underside to a smaller radius than the smallest bore the tool could be used in. (I smashed the carbide tool with a hammer, then brazed a suitable shaped piece onto an old boring bar and ground it afresh with a carborundum stone, before I found out about the new diamond "stones".).
  • Post#102 and a few following discussion points: I have recently been boring a cylinder - using my cheap and nasty mill-drill. A perfect bore - as far as I can measure... See pickies attached. Bore is perpendicular to one end face - as I sat it on parallels while setting the vice. The other face and bore were machined in the same setting. (locked bed). I think this is self-explanatory? Oh, it also shows I don't just write "boring" stuff, but practice a little boring, myself. The calliper was set to "just touching" and measured in a micrometer pre-set to the size I expected, then +0.001" and -0.001" settings until I got "exactly" the same touching feel. If you "screw" the micrometer onto the comparator, you cannot simulate that "feel". It is the "comparator" hand that has the feel, not the measuring gauge. Callipers just happen to be my preferred "comparator".
  • On Lapping the bore - see my comments back around post #104-ish (or wherever) about honing: You are ONLY going to take off the machining peaks, not the whole machining marks, otherwise you risk losing all the PRECISION MACHINING of the shape of the bore. If the V-shaped valleys are (say ) 10 microns deep, you only want to remove "Max" 5 microns. Lapping/honing is NOT the right way to get size of fit, except within the scope of the surface finish from machining. Take out 0.001" with a hone and you'll have to make a new piston - to avoid the noisy, damaging piston slap.
Enjoy,
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P1202361.JPG

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Ken
 
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Brian Rupnow

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Bob--the cylinder looks good. Try and make the o.d. of the piston so that it is a light press thru fit into the cylinder. You should be able to press the piston all the way thru the cylinder bore with your fingers, but if you stand the cylinder on end, the cylinder shouldn't free-fall thru the bore.
 

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