Double acting Double cylinder Oscillator

[NickG]

I've just been publicly whipped by someone on another forum. I had suggested that the engine would run "smoother" with better balance if the crankshaft was set up for 180 degrees. I was wrong.  With the crank throws at 180 degrees, you only get a power stroke twice in one full revolution of the crankshaft. With the crankshaft set for 90 degrees, you not only get self starting capability, you also get a power stroke every 90 degrees, so consequently the engine should run much smoother and slower with a 90 degree crank.---Brian

I was going to say the same then saw this post. Still, will be interesting to see the real difference if you can configure both ways.


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[Brian Rupnow]

In the picture you see $105 worth of material. $25 for the 2" diameter cast iron and $80 for the aluminum angle and 2" thick bar. I worked for about 3 hours to salvage $50 worth of bronze that I had laying around my shop.--Not very sound economics, but these small engines never make sense  from a $$ point of view. I have finished turning the two cylinder end caps for the non rod ends, and I have  the material for the other two cylinder caps up in the lathe. That will be tomorrows job.

[NickG]

Brian, why is it costing so much? I reckon I could get enough material for 10 engines for that price over here.


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[Brian Rupnow]

I pay that much because that is what material costs in Canada. I don't know where you are, but if you can buy the same material cheaper, then I'm happy for you.

[NickG]

Sorry, It just sounds an awful lot, it’s a shame that.


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[Jo]

Nick: Half the dollar cost to get an idea of the cost in pounds … College metals would charge more than that over here 

Jo

[Jasonb]

As Jo says 12" of 2" CI bar would be about £25-28 here so actually more than Brian is paying. Those a quiet big lumps of metal in the photo.

[Brian Rupnow]

This morning I finished machining the cylinder end caps, except for the counterbored holes for #6 shcs. I managed to break my 1/4" reamer. It started to squeal a bit and then "grabbed" in the bronze and twisted off. That reamer owes me nothing. I've had it for 10 years now, and it has reamed a thousand holes. It was getting dull anyways, and I don't think you can sharpen a reamer without it ending up "undersize". If you wonder why the counterbore in the non rod end caps is so deep, it's because the one piece of bronze I scrounged up had a deep drill hole at that end, and I had to go deep enough to get past the drilled hole. It won't affect the way the engine runs, as it's just a cosmetic feature anyways.

[NickG]

Fair enough if he bought a foot of each. But you can buy large by the inch here. Those two pieces of aluminium £40? A foot of each I could possibly understand.


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[Brian Rupnow]

Cylinder end caps are finished, and I'm done for the day.  Each end cap has a milled pocket  to let air into or out of the cylinder. There will be a few holes in the cylinder body that connect to these pockets, and as the engine oscillates the appropriate holes will be covered and uncovered.

[Brian Rupnow]

Nick--The 2" diameter cast iron was 12" long for $25. Somewhere in that price, there is a cutting charge for the worker to pull a length out of the rack, take it over to the saw, cut off what I need, and then return what is left to the rack. There will be enough in that 12" length to build two or even three engines. If I bought a number of shorter pieces, I would have to pay that cutting charge every time, and the guys I buy it from would hate me. The aluminum angle is 6" x 6" x 1/2" x 16" long, the 6" x 2" aluminum bar is 12" long. The angle and the bar were purchased at a different shop. It made my eyes water a little bit when I paid $80 for the aluminum, but unless I find another supplier right here in my home town, then I pay the price.--And really,--what would you have to pay for the same material?

[Jasonb]

It's the same here Brian, as I said about £25-28 for a foot length but if you buy by the inch you are looking at something like £6 and inch

Nick try this e-bay shop and see how the price goes up if you buy the shorter lengths, College that Jo mentioned are about £6.50 an inch too but don't reduce it for longer length so you pay about £80 for a foot

https://www.ebay.co.uk/itm/50mm-approx-2-dia-meehanite-cast-iron-round-bar-1-12-lengths/263651805198?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D31d599fa697e4da2ae4aa96d840677c1%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D263651805198%26itm%3D263651805198&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3A744bd1ab-611a-11e8-997a-74dbd18076f8%7Cparentrq%3A9de914f31630a688a74dd2d7fffd297c%7Ciid%3A1

[Bluechip]

This place is about the cheapest I know for aluminium. There may be better deals around in UK locally

www.aluminiumwarehouse.co.uk/6-in-x-6-in-x-1-2-in-aluminum-angle

To the best of my knowledge they will not supply bespoke lengths of angle.

It ain't free by any means.

Brian is quite right to point out the 'hidden' costs. As a percentage they can be very significant.

( Some years  ago a shop in Derby was selling transistors in singles actually made a loss on each if you work it out. A 2N2907 was 6p,  by the time the assistant had got it, put it in a little bag, taken the cash, possibly given change about 5 mins. had elapsed. At that time the labour rate for a shop assistant was far more than some 72p per hour! )

Dave

[NickG]

Haven’t checked it all but as Jason says about £25 for a foot of 2” cast iron. Where I go it is sold by the inch at £2.16.


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[Art K]

I have to admit being on vacation and missing a bit. Gas_mantle your link had me chasing down the rabbit hole and finding Fred Dibnah. I was loaned some of his videos some time ago and the boat made me think of him. Won't get me climbing a 150 foot ladder.
Art