Author Topic: Halfa, a DOHC inline Twin  (Read 21957 times)

Offline RReid

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Re: Halfa, a DOHC inline Twin
« Reply #330 on: May 31, 2023, 01:02:07 AM »
Thank you, Mike and Charles. I appreciate and understand the advice.

I have two generic ATV coils of the same type sold by the Howells, and they've both worked so far in bench tests. I also have a dual output coil coming that's meant for Briggs & Stratton twins. The vendor didn't list any specs for that one, but it was cheap enough to just buy. If the primary winding resistance isn't as recommended for the TIM-6 I won't use it. In which case I've also found a more expensive (~$45) "Dynatek style" dual coil with appropriate winding resistance that is an option, or I could just order a second module and treat each cylinder to its own ignition system using the ATV coils.
Regards,
Ron

Offline RReid

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Re: Halfa, a DOHC inline Twin
« Reply #331 on: June 01, 2023, 12:59:47 AM »
The low cost, dual output coil of unknown spec I mentioned earlier arrived today. I was hoping for a primary resistance of between 1.5 and 2 Ohms, and that's what this one has. Yay! Hooking it up to the the TIM-6 module and waving a magnet over the Hall sensor gave two good sparks. Yay again!


Speaking of magnets, they are going to go into the flywheel. I'll be using two 1/8” diameter magnets side by side to get the correct dwell angle. Since the flywheel is steel, I needto first embed a non-magnetic plug. I made a 1/2” diameter plug from brass, and JB Welded that into a flat bottomed hole drilled into engine side of the flywheel.




I'll let the glop cure until tomorrow, then poke in the holes for the magnets themselves and get them bonded in.
Regards,
Ron

Offline ddmckee54

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Re: Halfa, a DOHC inline Twin
« Reply #332 on: June 01, 2023, 07:33:16 PM »
Ron:

OK, the brass plug I can understand since it's non-ferrous and will disrupt the magnetic field lines.  But if you haven't installed the magnet yet, what's that in the center of the brass plug?

Is that just an optical illusion?

Don

Offline RReid

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Re: Halfa, a DOHC inline Twin
« Reply #333 on: June 01, 2023, 08:45:06 PM »
Hello Don. That's not exactly an optical illusion, but it is an artifact of the machining marks. That's the surface left in the brass by the parting tool, and the change in appearance may represent the point at which I paused to break the edge of the parting cut with a small file, which is my usual practice. Here's a photo with the magnets now installed.


They are a nice snug fit, so I didn't feel any chemical bonding was needed. Which meant I could immediately verify the result with the flywheel on the crankshaft and the Hall affixed to the engine - and got more LED flashing and plug sparking.  :whoohoo:
Regards,
Ron

Offline RReid

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Re: Halfa, a DOHC inline Twin
« Reply #334 on: June 07, 2023, 12:59:01 AM »
Yesterday I made the first attempts at starting this engine. Got some pops, including a couple of fairly strong ones, but no joy just yet. Still, it was encouraging as at least it seemed willing.

I did find that the #1 intake valve is not quite sealing fully, as I could see fuel in the fuel line being pushed back toward the tank on the compression stroke. Hopefully a bit more fettling of the valve/valve seat junction will address that. I also decided the piston o-ring grooves aren't deep enough and are producing too much friction in the bore. Unfortunately there is not much meat between the bottom of the groove and the conrod well inside the piston, and on the first one I tackled I went just a shade too far. So I'm making a new piston. For the other one I took I took a bit less off and got a better result.
Regards,
Ron

Online Kim

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Re: Halfa, a DOHC inline Twin
« Reply #335 on: June 07, 2023, 01:47:57 AM »
Encouraging pops are good!  :ThumbsUp: :popcorn:

I'm sure you'll work out all the many subtle kinks that are precluding a long series of sustained pops! :)

Kim
« Last Edit: June 07, 2023, 06:07:20 PM by Kim »

Offline Admiral_dk

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Re: Halfa, a DOHC inline Twin
« Reply #336 on: June 07, 2023, 10:06:07 AM »
Progress - even if not what you hoped for - but Pops are always better than silence  ;)

I'm sure you will solve this one too  :ThumbsUp:

Per            :cheers:

Offline RReid

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Re: Halfa, a DOHC inline Twin
« Reply #337 on: June 07, 2023, 03:17:13 PM »
Kim and Per - Thank you both! :cheers:
It's a process for sure, but I'll get there.
Regards,
Ron

Offline RReid

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Re: Halfa, a DOHC inline Twin
« Reply #338 on: June 09, 2023, 08:28:34 PM »
Well, it runs! I've gone from pops to quick bursts to finally a run long enough to pickup the camera, turn it on, and start a video. The actual run was maybe twice as long as what I captured. The task now is to get it to run as long as I want it to, not as long as it wants to.
<a href="https://www.youtube.com/watch?v=OQLor5iXTWM" target="_blank">http://www.youtube.com/watch?v=OQLor5iXTWM</a>
« Last Edit: June 10, 2023, 01:25:29 AM by RReid »
Regards,
Ron

Online Kim

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Re: Halfa, a DOHC inline Twin
« Reply #339 on: June 09, 2023, 10:40:05 PM »
Congratulations, Ron!  That is a HUGE step!  It's really a runner now!  :ThumbsUp: :popcorn:
Kim

Offline Dave Otto

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Re: Halfa, a DOHC inline Twin
« Reply #340 on: June 09, 2023, 11:49:52 PM »
Congrats on the first pops Ron!  :ThumbsUp:

Dave

Offline RReid

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Re: Halfa, a DOHC inline Twin
« Reply #341 on: June 10, 2023, 03:21:52 AM »
Thank you, Kim!
Thank you, Dave!

Regards,
Ron

Online Charles Lamont

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Re: Halfa, a DOHC inline Twin
« Reply #342 on: June 10, 2023, 09:04:22 AM »
Sounds very promising

Offline Admiral_dk

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Re: Halfa, a DOHC inline Twin
« Reply #343 on: June 10, 2023, 10:04:25 AM »
Nice Idle sound - it should be easier to solve the last bits or it might just improve with running time  :cartwheel:

Another one to be happy with Ron  :cheers:

Per

Offline Brendon M

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Re: Halfa, a DOHC inline Twin
« Reply #344 on: June 10, 2023, 01:37:09 PM »
Fantastic news! Congratulations :)
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