Tentative first Four stroke

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One of the results of mixing imperial and metric designs is that you always miss out on the appropriate tools. Off-size drills are the favourite lacking tools. As I mentioned on another forum I started my career in the great Machine Shop of Philips (that now under another name produces the positioning hardware in the ASML chip making machines). An old hand in the shop once showed me how to grind a drill for an off-size. In principle it is quite simple. Say you need to drill dia 7,8 mm. You take the next smaller drill size available, say dia 7,5 mm. Difference is 0,3 mm. Now you grind the point of the drill half the difference i.e. 0,15 mm excentric. It takes building up some experience, but it works well. As long as you start drilling from a good starting indentation, so no centerdrill but a short stiff 120 degree top angle starting drill. For a blind hole this works ok, with a thru hole you put a sacrificial piece of material underneath.
 
It's very easy to just substitute the nearest standard metric size on the Webster, for mine I just printed out the plans and annotated them with my alternate sizes as I made parts. Most bolts ended up being M3 (a couple of the larger ones were M4), shafts were made from standard metric sizes of silver steel, etc.

There are a few improvements to the design that can easily be incorporated into it. The main one I suggest is to add a counterbalance to the crankshaft. Mine has one and still shakes like crazy, so I'd hate to think what the stock design is like! If I had my time over again I'd also put a keyway in the crankshaft and the flywheel rather than relying on roll pins as in the stock design, as my roll pins worked loose during a power stroke and shattered my cast iron flywheel hub.
 
Robin
I would also vote for the Webster as a starter engine. I have made (making) the Kiwi and I must advise that there are many tricky machining operations not to mention castings which are on the dimensional limit. A mill is a necessarlty. There are however some excellent posts on the building process.
Best of luck!
Mike
 
I wonder at the problems some people have with metrication. I was reading recently of a British Motorcycle from 1930s with 65mm bore and 82mm stroke, while the rest of the engine was imperial sizes. As far as I know, only the USA used imperial bores and strokes?
In the 1960s, when I was re-boring car cylinder blocks, all the pistons and crank journals were metric standard sizes with imperial over-sizes. E.g. a 65mm piston with 0.020" oversize.
We just got on with it and converted from tables posted on the wall of the shop.
K2
 
I think the metric/imperial discussion will go on for ever and I don't think that is a problem! I work with both systems and continually convert between the 2 systems. I usually keep my DRO on metric and my mics and vernier will switch. I keep a conversion chart on the wall and offer this as a simply way to keep tabs on dimensions.
Enjoy!
Mike
 

Attachments

  • Imperial-Decimal-Metric.pdf
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It does need some careful application when mixed dimensions are used. There was a Mars lander that crashed - allegedly because it was planned for the parachute to open at some value in metres, but was set for that value in feet.... Ooops!
I had a colleague in Korea measured something in Imperial inches, but the local manufacturer used Korean inches to make it.. There are 10 Korean inches to the foot = 12 Imperial inches... The Korean steel rule had K" on one side and I" on the other....

K2
 
Never heard of Korean inches - I can only just coup with American gallons! When I worked in the US I purchased my steel rules there - inches on both sides and tape measures in inches so no confusion. I now have separate rules in inches and metric. Interestingly I make fewer mistakes using an imperial tape than a metric tape probably because the numbers are clearer and the numbers smaller for the same dimension.

I can however confirm that I have no hang-up about either system!
Mike
 
Hi Tom
I didn't think the site would accept Excel files. It turns out that .xls will load but .xlsx will not. I removed all calculations so I believe this is a true copy of the pdf I previously posted.

I find I use this chart all the time!

Thanks

Mike
 

Attachments

  • Imperial-Decimal-Metric to 1-5inch - 2003 format.xls
    40.5 KB · Views: 20
Hi Tom
I didn't think the site would accept Excel files. It turns out that .xls will load but .xlsx will not. I removed all calculations so I believe this is a true copy of the pdf I previously posted.

I find I use this chart all the time!

Thanks

Mike
I think I remember that one work-around for file types that are not accepted is to put them into a .zip file. Can anyone else confirm this?
 
Andy. Yes you can ZIP them but many people don't like ZIPed files as they can be a security risk - but I guess that comment could apply to most attachments.

Fortunately Microsoft allows you to save in many new and old formats. Interestingly I always save my AutoCad (2D) files in a 2000 dxf format so I know the file may be opened in any version of AutoCad!
Mike
 
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