V-twin compressor pump...

[Ian S C]

vile fly, I have a small set of kitchen scales, and things like that con rod get weighed, machined, weighed again, just to see how much weight I can get rid of, its amazing how much you can lose, and every gram/ounce, as long as you leave enough strength, helps. Extra weight means more friction. A compressor is built heavier than a motor, its working at high compression, and needs a strong con rod and crankshaft. Ian S C

[bowie]

I'm doing this project as well but on a 2hp model. I've modified the heads and taken off the bearings so far. I'm taking a bit different approach so Im following this thread carefully. Just reading this thread I've learned a great deal that will save me some time.

Those bearings were pretty tough to get off. I had to sacrifice a chisel. They had to go, they are simply awful. Taking off the Piston rings freed it up quite a bit. Connecting rods are much lighter than expected, the pistons weighs more. Im going to change out everything except the

If anyone has a good source on super-slick bearings please let me know.

[jimlarsen]

A good supplier of bearings in the US is Applied Industrial Technologies.
http://www.applied.com/

They offer a free catalog. It is like a dream book for engineers.

[bowie]

A good supplier of bearings in the US is Applied Industrial Technologies.
http://www.applied.com/

They offer a free catalog. It is like a dream book for engineers.

I cant wait to get it. Thanks!

[Ian S C]

bowie, theres a fair chance if you are going to use original pistons, you can get rid of a lot of weight from them. With the piston mounted in the chuck, held by the head you'll be able to thin the skirt up to the gudgen bosses. Then try and take some thing off the inside of the head of the piston, and take some metal off the bosses. Ian S C

[vile_fly]

Wow. I leave for a moment, and it takes off on its own. Nice to meet you, bowie. Yours may very well end up better than mine, since I never have done this on such a big scale. I think it is important for us to go in different directions so the we can explore the potential of this configuration fully. Did you say you were keeping the original crankshaft? Seems a bit heavy to me. I will more than likely end up narrowing my connecting rods to match the skinny bearings I picked up on ebay. I just got to make sure that I get the cylinder heads right.

I will be making several versions of cylinder heads with different diameter tubing. 3/16", 1/4", and 5/16" o.d. tubing will be used. I haven't had much time to get much further as of late, but hopefully I will have the hot side all wrapped up. As for bearings, I have found out using a skinnier bearing will reduce the frictional surface area. I have found the McMaster-Carr website to be useful for finding the industrial bearing number and for many other supplies. They ship pretty fast in the U.S.

http://www.mcmaster.com

[bowie]

bowie, theres a fair chance if you are going to use original pistons, you can get rid of a lot of weight from them. With the piston mounted in the chuck, held by the head you'll be able to thin the skirt up to the gudgen bosses. Then try and take some thing off the inside of the head of the piston, and take some metal off the bosses. Ian S C

Thats what Ive been thinking about but Im going to hold off until I can figure out the right displacer before I modify the pistons. I wish I had more time these days!

[bowie]

Wow. I leave for a moment, and it takes off on its own. Nice to meet you, bowie. Yours may very well end up better than mine, since I never have done this on such a big scale. I think it is important for us to go in different directions so the we can explore the potential of this configuration fully. Did you say you were keeping the original crankshaft? Seems a bit heavy to me. I will more than likely end up narrowing my connecting rods to match the skinny bearings I picked up on ebay. I just got to make sure that I get the cylinder heads right.

I will be making several versions of cylinder heads with different diameter tubing. 3/16", 1/4", and 5/16" o.d. tubing will be used. I haven't had much time to get much further as of late, but hopefully I will have the hot side all wrapped up. As for bearings, I have found out using a skinnier bearing will reduce the frictional surface area. I have found the McMaster-Carr website to be useful for finding the industrial bearing number and for many other supplies. They ship pretty fast in the U.S.

http://www.mcmaster.com

Well thank you for your kinds words and nice to meet u too. McMaster Carr is awesome. I have a feeling both of us are going to be successful with differing approaches. Yes orig crankshaft is quite husky. Im going to keep it as stock as possible. At this point I have loosened it up enough that the flwywheel is turning quite easily. I cant make any decisons until those bearings get here so tomorrow Im just going to start the regenerator. I look forward to learning from you.

[bowie]

I installed new crankshaft bearings today...Nachi NU204 (20x47mm) and NU205 (25x52mm) and I must say I am very impressed with the huge reduction in friction. The crank is now turning very freely. It's hard to imagine finding bearings any faster than these.

Ian, I did exactly as you stated and trimmed up the pistons, a great deal of weight is gone!

Let's see how things go with the displacer tomorrow.

Fly, I hope your work is going well. I am very excited to see your progress. I hope at some point we can compare notes.

[vile_fly]

Had to rebuild my transmission in my truck, so I lost a bit of time and money. So, I am posting a picture showing how the hot head will assemble. Basically, the two steel and two copper plates will go together with the bubble flares on the tubes trapped between the 14-gauge copper sheet metal plates with the steel plates on the outside. A stainless foil gasket will be against the top of the cylinder to reduce any thermal short circuit. I decided against using copper washers, and went with this. Oh, and this weekend is a bust, also. Have to go to seminars all weekend.

[bowie]

Sorry to hear that Fly, about the transmission that is, and the seminars, yikes. Hot head is looking tight!

Not much going on so far on the outside for me. I pieced it back together for this picture. Thats the heatsink on the cold side that has a copper plug which nests inside the exisiting cold cylinder head with small heatfins.

I ve been turning the crankshaft and now its really loose.

I've been sketching out regenerators but in the end it's most likely going to be a large heatsink with a steelwool chamber.

[vile_fly]

Not to worry, I am still at it. It looks like I may favor the 1/4" (6mm) tubing in my build. The key to sealing is going to be the enlarging of the pilot holes of the upper plate to allow pass-through for the tubing. All drill holes were started with the 4 pieces bolted together. (2 copper, 2 steel) The inside diameter of the tubing was matched to a drill bit. Behind both is the 3/16" plates. Most of you guys already know this anyway, but some beginners with fewer resources may find it useful.
Frankly, I could have used a better type of flare besides the metric bubble flare, (push-connect fuel line flare) but the flaring tool for those is prohibitively expensive ($400.00 typical), so I am sticking with it to keep a cheap ISO-type standard going in this project. (By the way, I have the flaring tool in my toolbox, because of my job)

6mm cylinder head.JPG (251.25 KiB) Viewed 9600 times

[Ian S C]

The flared tubes gets around the usual brazing, I hope it will be a possitive seal under heat. I can imagine stainless tubes TIG welded to a stainless head. Some of the more sophistecated motors have had the tubes brazed in by a vacuum system, using a high temperature alloy. If your system works, it will be a great saving in the construction. Ian S C

[vile_fly]

I think I should be successful if I don't exceed 1984.32 °F (1084.62 °C), Ian. I can also layer as many annealed copper gaskets as needed, too. I will make it work if at all possible. Here's a shot that shows the sealing surface area that will press against the tip of the bubble flares.
And now, a word on tube displacement.......
3/16" (4.7mm) O.D. brake line tubing displaces 2.414cc per foot [1/8" I.D.]
1/4" (6.35mm) O.D. brake line tubing displaces 5.431cc per foot [3/16" I.D.]
5/16" (7.93mm) O.D. brake line tubing displaces 9.656cc per foot [1/4" I.D.]
3/8" (9.52mm) O.D. brake line tubing displaces 15.088cc per foot. [5/16" I.D.]

My de-stroked engine will displace about 150cc per cylinder. [300cc total] Stock displacement is 300cc per cylinder. [600cc total]
This will impose some limitations on how much tubing I can use. Total dead volume (including regenerator) cannot be allowed to exceed engine displacement, according to my research. This is the part where I count and measure every tube, since not all will be able to be the same length after a 90 degree turn.

[Ian S C]

vile fly, I don't think you have too much to worry about with dead space. I have an artical in Model Engineering (1977) by W.D.Urwick on Stirling Engines, he did some experiments, and ended up with 6ft of rubber hose conecting the power cylinder to the displacer, with very little change in performance, just a pulsing in the tube. Ian S C