V-twin engine from scratch - yet another interpretation of how (not) to build a

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madjackghengis:
Looking good Sorveltaja, if the push rod angle is too great, and that depends a lot on the depth of your ends, and how much your rockers flex on their stanchion, set your valves half way open, and your cam half way up, line the valve end of the rocker perpendicular to the valve travel, and split the angles between the rocker and pushrod, and the lifter and pushrod, and make the rocker such that all these things come to be at the same time, or are adjustable to come together at the same time. As long as they open and close, and nothing jumps out of place, they ought to work fine. After all Harleys run, and they don't bother with engineering. Harley engines are still dealing with a cylinder stud problem which the Japanese bikes had figured out in the early sixties, and have never had a problem with, while Harley's still going the exact wrong direction toward "curing" their problem. Mad Jack :thumbup:

sorveltaja:
Thanks for replies :wave:.

Bit of progress:

Valves are lapped, and installed with springs, and I threaded both inlet, and exhaust ports to M5. Also flat surfaces were milled for nuts.

At this stage, everything seems to rotate and move freely when rotating manually, except the pistons are still bit tight.

Mad jack, thanks for the tips :thumbup:.

Making longer rocker arms might be one possible option also, to lessen the angular stress.

Forthcoming run-in sessions on the lathe hopefully reveal if such problems exist on the engine :coffee:.

Stilldrillin:

--- Quote from: sorveltaja on April 05, 2010, 03:02:59 PM ---
Forthcoming run-in sessions on the lathe hopefully reveal if such problems exist on the engine :coffee:.

--- End quote ---

Good Luck! :thumbup:

David D

sorveltaja:
Crankshaft started to wobble during the run-in session. Reason:

One of the silver solderings failed. Similar thing happened on my previous test engine also :scratch:.

I guess the reason for that is, that I have made shaft and holes too close fit, so there isn't much room for solder.

Anyways, I replaced the end axles, reamed holes to 4mm(0.157"), and drilled them partially to 4.1mm(0.161"), to provide bit more room for silver solder to flow between the parts.

madjackghengis:
Hi Sorveltaja, current studies show the strongest joint of this type is a technically proper press fit, lubricated with locktite, I would use 609 stud and bearing mount, and the smoothest surfaces of both the shaft ends and the holes they fit in being the last factor. If you can freeze the shafts, heat the wheels, and make it a shrink fit with the above properties, it should be stronger than a single manufactured piece. When I braze or silver solder such a joint, I almost always knurl the shaft ends, but avoid doing so in such circumstances that require accuracy in more than one plane as knurling allows shafts to wobble and the like. Press fits are best served up with square shoulders to stop against, and wheels faced dead parallel to each other with either a jig or alignment pins to allow the pressing be done in one fell swoop. If the crank is never to come apart again, you can drill holes for pins to run through both the crank pin, and the two shafts once they are all aligned, I like taper pins, and peening the small end over, after it comes out the other end. I wish I could have discovered my shafts were not straight by running, instead of by dial indicator, at least it would have seemed like progress. Looking good otherwise, you should have this solved in a jif, and be well running soon.- :headbang: Mad Jack

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