Today's work on the Onan opposed twin half scale. Photo 1 the valves and seats 2 shop made saddle stop 3 valve guide insert 4 pressing in the insert 5 the press 6 cutting the seat 7 drilling the guide. You can check out the Grandchester Model Live Steam Club Inc in our website, or in Australia Chanel 7s Creek to Coast Saturday 20th March.
Opposed twin Onan engine in half scale
- Thread starter teeleevs
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Thanks Mark, they took 2 hours to produce our 5 minutes of fame see if you can view this link
Hi all I have not been on for a while, had carpal tunnel operations March 25th, all's well. Photos 1 and 2, drilling the ports, 3, welding the exhaust system 4 and 5, muffler and intake manifold, just tacked in the photos, 6, starter in place. Maybe a trial start soon.
Ted from down under
Ted from down under
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After much work the Onan finally kicked in and ran. Some work to do yet, maybe a bought carby might improve things, we had it running on a petrol soaked rag, and on a gas torch.It runs.
thanks for watching Ted from down under
thanks for watching Ted from down under
the engineer
Well-Known Member
brilliant well done
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That runs very well, and smoothly.
I'm lookig forward to the fully finished version.
Congratulations,
--ShopShoe
I'm lookig forward to the fully finished version.
Congratulations,
--ShopShoe
Thanks Guys, it does run smoothly bolted down to a one ton lathe. I spent the day attending to oil leaks and other problems, perhaps another day or two before we try again, then I need to make the most visible part, the fan cover.
Thanks for watching
Ted
Thanks for watching
Ted
Someone suggested that the way I made up the crankshaft was risky, well sure enough it came back to bight me, after the run & after a few more trial starts the engine got stiff & the flywheel was noticeably out true (photo1) So the Onan looks like this at the moment, (photo 2) We replaced the bigend inner bushes with a hardened steel pins, (photo 3) Rebored the crank webs, pressed the pins in, tack welded after lining up each part, (photo 4) All ready to go back together. (Photo 5)
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AlexS
Member
Welding the crank is the wat to go with a pressed crank. Would likely to see it running again!
Thanks AlexS We have had it running again, we started it on the lathe and lets say I will not need to oil the lathe for a while! Still having trouble with valve sealing, had issues with timing and in the process put a piece of wire through the plug hole, finished up bending the intake valves (when I say bending ? a .001" miss-alignment would cause a bad leak in such a small part) I re-lapped the more serious one but both need more attention. During the course of trying to get a re-start I finished up with twin carbs on it (Honda weed basher ones) I have given the Onan a rest and attended to an upgrade of the tractor, replacing the 46 year old Suzuki 2 stroke jeep engine with a brand new Chinese V twin air cooled one, sounds good.
Thanks for watching. Ted from down under.
The latest on the Onan opposed twin in half scale, it runs The Grandchester Model Live Steam Club Queensland Australia (of which I am a member) a new engineering trophy has been created in honour of 2 very resourceful and respected engineering men, it is my honour to be the first person to win it with my Onan engine. See photo. Apparently I need to work on the video.
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You probably know this, but it was a recent lesson to me, I was rebuilding a 2.75HP Lauson engine (USA made in Wisconsin, and now owned by Tecumseh) they used a check valve, which I now know was common so that the crank case operated with negative pressure. It had ball bearings for the mains, and just simple metal shields, and no rubber seals, and never leaked oil. I see this in all engines now, just never realized they did this. I never thought what the PCV was for on my V8 engine I had as a teenager.
I assume you put such a check valve on your engine to fix the oil leak issue.
That engine runs nice!
I just rebuilt a Fairmont engine for my brother for his two seater Fairmont , the engine was a single cylinder with hopper style cooling and a radiator on the hopper. Unusual engine with poppet style valves in the carb/manifold!
Had it running nicely just last Thursday.
cheers
Mark
Had it running nicely just last Thursday.
cheers
Mark
Yes Ignator I had too strong a spring in the valve and nowhere for the oil to go. The PCV valve on a multi cylinder engine actually works differently, it allows a small draw on the crank case at idle and a large amount at revs. My Onan powered welder began to leak at rear main oil seal but I couldn't remove the generator to replace it subsiquent owner ran it out of oil, problem I found out recently on the web if the valve clogs it will cause oil leaks. Single cylinder engine, (also opposed twin and vee twin) have a great amount of crank case volume changes due to piston displacement, I found this out when I cut down a Toyota 6 and made a single, remembered that Brigs and Straten have a valve in the breather, solved the problem. On my model I have used 2 truck compressor silencers for air cleaners and one to separate the oil blown up the breather valve, all working fine,
Some interesting engines about, some 2 stroke boat engines run with valves in the manifolds, allows for oil in the sump. Ted
