Vertical Cylinder I.C. Rupnow engine

[RayW]

Hi Brian.
Love the engine and glad to see that you are making it work for a living, and what a useful piece of equipment, a ball raiser!! No man should be without one.
Don't know if you have seen the updates I have been posting on my Otto build, but it is going well and I think the end is somewhere in sight now.

[Brian Rupnow]

Heads up builders---The two cylinder head bolts that fit into the holes on the sloping side of the head--make sure that they aren't too long. I just noticed today that on my engine those two bolts were too long and had actually bent the third fin down from the top of the cylinder. Considering that the cylinder is all made from cast iron, I'm lucky the cooling fin didn't break.

[Brian Rupnow]

When you go to build the carburetor, that inlet cone on the main body, (that for some perfectly weird reason is dimensioned at 15.77 degrees included angle) isn't all that terribly critical, at least not to two decimal places. If you have a very small boring tool, then you can simply set your topslide over to 8 degrees and bore the taper after the 0.195 diameter thru-hole has been put in. On the other hand, if you don't have a very small boring tool you can build a D-bit like the one in the attached drawing. (which is what I did). There is a little story behind this. I first paid good money for a tapered spiral reamer with a 16 degree included angle to use for this operation. In the process of posting about it, I was warned by Gail from New Mexico that a tapered spiral reamer would "grab" and taking advantage of any backlash in the leadscrew nut would pull itself very deeply into the work. I decided to try this on a test piece of aluminum with a 0.195" hole in it. Gail was right. As soon as it started to cut, it grabbed and pulled itself into the work so badly that it stalled the lathe. so---I built this D bit to do the job, and it worked like a charm. The one critical thing on that carburetor body is that the taper must stop before it reaches the 0.394" center bore of the carburetor. There must be at least some of the 0.195" diameter hole between the end of the taper and that .394" thru-hole, otherwise the carburetor won't work right.

[Ian S C]

A taper reamer for this sort of thing should have a reverse spiral, so it tends to be pushed out, rather than screws in, the D bit is the best way to go.
Ian S C

[Brian Rupnow]

For those of you who are toiling away on this build, I have a bit of advice for setting up the carburetor to run the engine. For an initial setting, open the needle valve one full turn. Set the throttle to about 1/4 of the way open. If you are lucky enough to have the engine start and run (hope--hope---) then let the engine warm up. Try screwing the needle valve in or out SLOWLY until the engine seems to be running at it's best. Back the throttle off until the engine is running at a medium idle, and set the idle adjustment screw so it prevents the throttle from closing any farther. At his point, you can start adjusting the air bleed screw. You will find that there will be a point of adjustment on the air bleed screw where the engine begins to rev faster. When this happens, adjust the idle adjustment screw to slow the engine down to it's original idle speed. Keep adjusting the air bleed screw until it doesn't change the engine rpm any farther, and lock it down there. I used the springs out of a pair of ball point pens and slipped them over both the idle adjustment screw and the air bleed screw, (captured under the head of the screws) to keep the screws from vibrating out of position. You will find that you probably have to cut the springs to the correct length.

[bruedney]

Hi Brian

Just letting you know I am looking to make your engine but in Metric.

I started today redrawing your plans in Autodesk Inventor. I must say that imperial to Metric conversion is not a fun pass time.

I belong to the same club as David Lloyd and he showed his build at club night a week ago.

Regards

Bruce

[Brian Rupnow]

Bruce--That is wonderful!!! When you get to the stage of making chips, please start a thread on your build.--Brian

[bruedney]

Hi Brian

I Have most of the major components drawn and assembled in Inventor and I just have a question about the amount of compression space when the piston is at TDC. It appears to be about 0.165" (4.2mm). Does that seem right?

Just wanting to confirm that I haven't made a gross error in my conversion calcs

Cheers

Bruce

[Brian Rupnow]

I just checked mine, and when it is at top dead center there is 5.8 mm from the top of the cylinder to the top of the piston. Best bet is to shorten the con rod 1.6 mm, or take 1.6 mm off the crown of the piston if there is room to do so. Note that when the piston is at bottom dead center the bottom of the piston skirt extends 2.03mm beyond the bottom of the cylinder.

[bruedney]

Thanks Brian

My calculations were with the cylinder head on (1.2mm boss) so I am pretty close. I will check the other dimensions as well.

Cheers

Bruce

[bruedney]

The gear cutting went very well. I have a set of dummy shafts set up at the correct center distance in a scrap of aluminum plate, and all the gears I cut are checked for correct mesh before I tear down my rotary table set-up.  The second picture shows both gears finished, and the hub ring attached to the smaller gear. I'm probably going to go ahead and finish the valve cam and install it on the large gear before I install the gears in the engine. I still don't have my oilite bushings anyways, so I may as well get the cam finished now.

Hi Brian

Can you please give us some details on the Gear cutter(s) you used to make your gears?

Cheers

Bruce

[Brian Rupnow]

I bought a complete set of 7 or 8 gear cutters for 24 Diametral Pitch gears from either Litlemachineshop.com or from travers.com and I bought the arbor they fit on at the same time. It cost me about $500 for everything, however the cutters may be purchased individually for about $45 each. You will need two different cutters to make those two gears, as each cutter will only do a certain "range" of teeth. You need a #7 cutter to make the 15 tooth gear and a #4 cutter to make the 30 tooth gear. In a pinch, you can make your own arbor. If you choose to use MOD gears of the same approximate diameters instead of the DP gears, you can do that as long as you keep the ratio at 2:1, and remember that the center to center distance of the gears (determined by the pitch diameters) is what establishes where the cam shaft hole sets in the main frame of the engine.

[bruedney]

Thanks Brian

Very helpful

I have nearly finished the metric conversion and redraw. Just need to do all the drawings now.

I have started to look at what stock I already have and what I need to buy.

I am going to start making swarf soon 

Cheers

Bruce

[roboguy]

Bruce, you are just too productive! You are putting the rest of us to shame.

Can't wait to see your build of Brian's engine. I'm almost motivated to give it a crack.

Cheers
James Fitzsimons

Sent from my SM-G920I using Tapatalk

[mnay]

Brian,
Great engine build article in Home Shop Machinist.
I look forward to the next issue.
Great engine for those of us that are not retired and don't have time for a radial or more complex engine.
Mike