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Author Topic: K&B Green Head 45  (Read 2805 times)

Online Robert Zambelli

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K&B Green Head 45
« on: May 17, 2025, 09:26:12 AM »
I acquired this engine in the lates 60s.
It has an internal balance wheel driven off the crankshaft.
The wheel supposedly cancels out vibration.
Well, it doesn't!
I mounted it on a test stand and then on a profile.
Made pretty impressive power but vibrated so much I thought the nose was going to break off!
Anyone have experience with this beast?
Inquiring minds want to know.

Bob Z.
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Offline Colin McRae

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Re: K&B Green Head 45
« Reply #1 on: May 17, 2025, 11:32:43 AM »
Did you also notice excessive vibration on the test stand, or just on the model?

I don't have specific experience with this engine, but I did have excessive vibration with a McCoy 35 on a CG Shoestring. Funny thing was I had the same engine on a Ringmaster with no undue vibration, but on the Shoestring some major vibration. Some type of resonance on the particular model/engine combination.

So, might your issue be the model/engine combination, and not just the engine?
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Online Brett Buck

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Re: K&B Green Head 45
« Reply #2 on: May 17, 2025, 03:23:53 PM »
Quote from: Robert Zambelli on May 17, 2025, 09:26:12 AM
I acquired this engine in the lates 60s.
It has an internal balance wheel driven off the crankshaft.
The wheel supposedly cancels out vibration.
Well, it doesn't!
I mounted it on a test stand and then on a profile.
Made pretty impressive power but vibrated so much I thought the nose was going to break off!
Anyone have experience with this beast?
Inquiring minds want to know.

    Are you sure the balance wheel is timed correctly with the rest of the engine? I haven't even seen one, but in other situations, you have to have the offset wheel/offset weight timed accurately, or it makes the vibration much worse (basically, doubles it).

    Brett
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Online Robert Zambelli

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Re: K&B Green Head 45
« Reply #3 on: May 17, 2025, 08:11:15 PM »
Colin - yes, it  also shook like hell on the test stand.

Brett - good point.
The wheel can only go in one way.
The face is flat except for a small recess to accept the crankpin extension.

BUT, I have a plan!
More to come.

Bob Z.
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Offline Brian Hampton

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Re: K&B Green Head 45
« Reply #4 on: May 17, 2025, 08:16:59 PM »
There's a test report of this engine at https://sceptreflight.com/Model%20Engine%20Tests/K&B%20Torpedo%2045%20RC%20%282%29.html describing the balance weight and how it's driven so it's impossible to time it incorrectly.
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Online Brett Buck

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Re: K&B Green Head 45
« Reply #5 on: May 17, 2025, 09:58:02 PM »
Quote from: Brian Hampton on May 17, 2025, 08:16:59 PM
There's a test report of this engine at https://sceptreflight.com/Model%20Engine%20Tests/K&B%20Torpedo%2045%20RC%20%282%29.html describing the balance weight and how it's driven so it's impossible to time it incorrectly.

    Oh, it's driven like a rear rotary valve, never mind!

      Brett
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Offline M Spencer

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Re: K&B Green Head 45
« Reply #6 on: May 18, 2025, 12:21:50 AM »
.
« Last Edit: May 26, 2025, 07:41:05 PM by M Spencer »
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Offline Dennis Toth

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Re: K&B Green Head 45
« Reply #7 on: May 28, 2025, 11:27:01 AM »
Bob, interesting to hear the K&B 45 is shaking so much. This was the engine Lew McFarland used in his Shark 45 design that was a very successful design. In the construction article he praised the engine as being light, powerful and smooth (https://outerzone.co.uk/plan_details.asp?ID=4557). He used a 11x6 Top Flite prop with 4 1/2oz tank. I'm wondering if someone had tried to grind off some of the either shaft or rear counterweight to save some weight or smooth the fuel flow?

Best,   DennisT
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Online Robert Zambelli

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Re: K&B Green Head 45
« Reply #8 on: May 28, 2025, 03:46:17 PM »
Thanks to all for the replies.
Dennis - My K&B 45 was virtually new, only broken in, never mounted.
Before running, I removed the backplate and noticed that everything was in place.
I ran it with a new, perfectly balanced Rev-Up 11-6 wood prop.
5% nitro, 50/50 lube.
Easy starting, revved effortlessly, shook like a whore in church.
My flying buddy Walt was good friends with Lou McFarland and Lou gave him a kit.
Per Lou's suggestion, he powered it with the same K&B 45 as mine.
Lou claimed that it was as smooth as an electric motor.

Bob Z.
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Offline Dennis Toth

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Re: K&B Green Head 45
« Reply #9 on: May 29, 2025, 11:07:11 AM »
Bob, is it possible that some dried out castor or other oil got pooled in the inside of the piston and causing it to be slightly heavier than normal?

Other thing to try to see if the piston side is heavy is take an off-balance prop and set it so the heavy blade is opposite of the piston (an old FOX 35 trick). If it smooths out a little you know where to look for something in the piston or piston machining.

Best,    DennisT
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Offline Dave Hull

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Re: K&B Green Head 45
« Reply #10 on: May 29, 2025, 02:10:37 PM »
Bob,

You might also check the track and pitch of the prop. If the track is way off, it can also cause problems. If one blade has more pitch than the other that can be an issue too.

Dave
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Online Robert Zambelli

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Re: K&B Green Head 45
« Reply #11 on: May 29, 2025, 05:49:27 PM »
Dennis - good suggestion. I will investigate.

Dave - I tried a number of different props, 11-5 and 11-6, both wood and plastic, all precisely balanced.
No change in vibration - still unacceptable.
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Offline GERALD WIMMER

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Re: K&B Green Head 45
« Reply #12 on: May 30, 2025, 04:30:18 AM »
Hello
All sounds rather puzzling . I repaired a K&B GH .45 for my brother with new old stock parts .
It ran very smoothly and seemed similar to the old Enya 45's I like.

Regards Gerald
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