Opposed twin Onan engine in half scale
- Thread starter teeleevs
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Hi Mark, the model, second pic, runs on 7 and a quarter inch track 184mm the engine is a Victa 160cc much modified, it will run either way, has car pointless ignition with 2 wings to activate the magnetic pickup 18 degrees before TDC in either direction. In operation the engine runs backward to its original direction smoothed out by a 5kg weight flywheel. Will pull easily 2 wagons loaded with 16 adults and children.
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Shortened Toyota engine.
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That looks like it took some doing to seal off all the coolant passages, especially in the cylinder head. That's an interesting project to complete.
AlexS
Member
Some people make from single engines multi, but you did the opposite!
Engine runs quit smooth on your video. Congrets for winning the price
Latest on the Onan opposed twin in half scale, have run it several times lately and it is starting better and will almost idle. Some more work, pictures 1-3, a few days ago this was a perfectly good 20lt drum (4 gallon) picked up on the side of the street (thrown out for annual trash pick up by council). Picture 4, making spot weldable nuts for the wire fan safety part.
Will look better with some paint. Picture 5, the back side, showing twin air filters and oil seperaater with drain back through rear bearing, coil and wires also fuel tubing, both carbies have their own fuel pumps worked by pressure variation in the valve covers.
Ted
Will look better with some paint. Picture 5, the back side, showing twin air filters and oil seperaater with drain back through rear bearing, coil and wires also fuel tubing, both carbies have their own fuel pumps worked by pressure variation in the valve covers.
Ted
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Your tin work is beautiful. Looks like this project is almost finished.
Yes but I have a porosity problem with the sump casting, it leaks oil when not in use, not very much but it only holds a cup full. Have to take things apart and seal it with Locktite. I know that the 1920s Buicks had the same problem with the crankcase castings in alloy.
Ted
I've seen single cylinder engines, like the Lauson I worked on that used a red oxide enamel paint in the interior side to seal iron casting from oil leaks.
Glyptal is a name that comes up for this paint. It's expensive at $50USD/quart.
Hopefully you can get the oil removed so you can seal it. Do you have a favorite solvent to do this? I ask, as I'm curious for any future issues I may have.
I use a product we call Acetone available from hardware's, there is another product the Auto Painter's use to remove grease and finger prints off cars before painting, Wax Off or similar.
Thanks for the questions,
Ted
I use Acetone as well, available in every home construction supply in gallon cans. It will curdle dry paint. Worse I seem to get skin problems on my fingers when using it. And it eats nitrile and latex gloves. Oddly it's sold as fingernail polish remover.
I've used denatured alcohol in recent times for cleaning metal before painting. That worked well getting residual grease and oil off an antique truck chassis.
By now, you probably have the crankcase sealed from oil leaks, and doing finish work on your engine.
An update on the Onan opposed twin in half scale, See it running After stripping it down and sealing some poor casting issues I still was not happy with starting and idling. Brian Rupnow's figures on cam design would have been very handy if he had uploaded them a couple of weeks earlier. Armed with DTI I began checking the valve events and was horrified with what I found and it actually ran, suffice it to say I wrote across my scribble paper. " This engine has a better chance of running backwards ." So I reworked the cam shaft, it ran much better but still not happy, it was obvious something was amiss when the heads ran at different temperatures. I removed the linkages from the carbies, wound the idle stops all the way in and started it up, then backing one screw out until I got near similar reading on both heads, refitted the linkages. It then sounded retarded, on checking the ignition timing it was firing at 8 degrees, I shifted the ignition pick-up back to where I originally had it. Now starting easily, even with a rope and once so far on the starter, but much better with a battery drill. It will idle down to 1200 Rpm and rev out to 4300 not bad but I never want to work it at that revs.
Ted from down under.
Ted from down under.
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More on the Onan opposed twin in half scale, after a lot of fiddling we reworked the manifold and set up single carby, runs and starts much better. Then we revisited the shop made carby with some cheating, fitting the fuel pump/diafragme block to the side of a block of alloy with my original throttle body on top, it starts much better will even start and run on one cylinder. I've experienced before once your solve one problem it will throw another up at you, now I'm having problems with crankcase vacuum and it's ability to work the fuel pump.
Ted from down under.
Picture 1 the bought carby, 2 ĺooks more original, 3 parts needed for the shop made carby, 4 & 5 final carby in place.
Ted from down under.
Picture 1 the bought carby, 2 ĺooks more original, 3 parts needed for the shop made carby, 4 & 5 final carby in place.
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Reasons I was not happy with the dual carbys was after only a few minutes running heat transferred to the carbys and petrol began to boil, we have seen this problem in older cars especially in tropical areas. The balance between the two was very difficult to achieve. I mentioned cheating above but the parts used only supplies the fuel to my throttle body which is fully adjustable and also the main jet advances with the throttle. All works fine now and it will start easily on the starter which doesn't swing it over all that quickly.
Ted from down under.
Happily creating swarf.
Ted from down under.
Happily creating swarf.
