Engine Vibe with Stroke Increase and Counterweight Deletion

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Martti Mattila

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Help needet, I have these silly engine conversion projects coin on. I ´m planning to use different motor crankshaft to get longer stroke. Case space is a problem exspecialy room for counterweights. I have studiet crankshaft vibration theories BUT they are all from racing enviroment talk. Nothing to us under 3000 rpm. direct driwe guyis. My Vauxhall from seventies doesend have counterweights, only heavy flywheel. I´m talkin straight four now. Do I need cw.s to crank that spins under 3000. Those old sidevalve Fords and Aircraft inlines have no cw.s. What if I cut them away.
 

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TFF

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If you cut them, they will act like an old style engine. Will it break? You will find out. It’s a do and see. I would think trying to keep as much as you can would mitigate it. It’s going to come down to how big and heavy the prop is and how much the crank wants to twist as to it surviving.
 

Martti Mattila

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If you cut them, they will act like an old style engine. Will it break? You will find out. It’s a do and see. I would think trying to keep as much as you can would mitigate it. It’s going to come down to how big and heavy the prop is and how much the crank wants to twist as to it surviving.
Thats were I am now leaving leaving as much as possible. From 66,6 mm. to 78 mm. now and running. But like to go 88mm. Honda crank or even 97 with Hyundai 2.4 l they all have close 95 mm. cylinder intervals. The only hope that stupid and envy has that it will not run.
 

TFF

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You still have rods and pistons that have to fit. That’s a pretty big jump if you go 97mm. You must have a very friendly crank grinder.
 

Martti Mattila

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Whittout internet no can do. Max Speedingrods tels what rods are in the world, lenght and diameters and you can try to find standart ones cheaper. Piston compression height varies too. Cylinders can be trimmed with Lathe and spacer plate thignes is my to choose. I only need to know how to add in math wise.
With this 78 mm. trow, deck high is les than original because Mazda Miata piston are shorter than originals.
Yes my engine machinining shop operator is hobbyist friendly because nowadays theres no other work. I bought this crank welding machine cheap but I ´m not planning to use it for now because theres the other option. But thanks for building up the cuts.
 

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proppastie

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I made drawings of machinery for a living ...that would be how I would try to find out if everything is going to fit before I started banging away.....Granted a crank case drawing is pretty complicated but you do not have to fully draw it to see what you need to see. Of course if you have parts in hand seeing how they fit will also work. Ballance and resonance vibration will be issues, this is not easy stuff...sounds like you are having fun.
 

Martti Mattila

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I have had short test run with 78mm. stroke, but not having it taken to the limit. It has a dual blugs but I havent got done the ignitionsystem for douplers. Like to have it totally independent like some things that I´v heard that flys. Plenty teething proplem for sure, but we need a hobby. And how good it is to have internet, if you wanna re educate your self from issues like: Piston ring end cap, Piston clearance, Bearing clearance, Con rod ratio. Induction air speed. Valve spring stifnes. and so on.
My mother language is Finnis but luckkily I can handle the engine enviromet vocabilary in English und bissen Deutch. I already know that 88 crank will reguire plenty case rework. Better run this 78 first and see what happens. But there is a notion that I have made. Motor mounts in inline engines are all in different breed comparing flat AC. engine. Trust side member look weaker than that one on up,sideways diagonals are not used, no space for them either. They usualy are calculated by professional AC. engineer so they must be ok. but they look weak. Many times the lover member in treadet for fine lenght adjustment.
This picture shows how badly Walter Mikron motor is burning oil and they only had 600 hours TBO if I remenber correctly. It too has this weak looking engine mount.
That plane has once had a world record from distance flying under 500kg. clas. 2700 kilometers from Madrid to my home town Turku Finland.
 

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TFF

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Is it oil or fuel or both? Could that carb can not lean out at altitude and were they running bean oil? 1960s metallurgy, machining, and operation is not as precise as now. In fact, today we know so much more, that we can cheap out and get similar performance, where past was using best available and still not right. I always try and put achievements into period context. Because it can be better today doesn’t erase the achievements then.

What case are you trying to use, and the other components? Curiosity. Because you are working it out gets different respect than someone just coming up with combinations on paper. Very old school making something work that’s not supposed to, is always interesting. On paper, not so much.
 

Martti Mattila

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I am so sorry that this same pic. is here again. but its more easy to tell what I´m doing. Motor on the right pic. is the one that I have build with not original cylinders and crank. This is a German NSU Prinz 1200 car motor from sixties. Fiedel Mynch build motocycles with that motor.
Mynch Mamoth was the name, it was imported to U.S. too. Cylinders are from Ukranian Dnepr bike and long crank is from VW K 70 car that was originaly NSU
K 70 but NSU went liquidation because they spent so much money to Wankel engined NSU RO 80. When NSU designed this watercooled e. they use aircooled as a pattern somehow. thats why cylinder interwals are the same. I can adjust the cylinder height with that spacer plate thignes that now is 20 mm. same plate works as a oil return chanel. When I cut cooling the ribs away from two side of the cylinders they went oval and a wrong direction and reguired force honing. I dit that by my self with cheap Indian made honing head. So there my tecnology compairs the old times. Pistons are Mazda Miata 78 mm.
Left pic. is from HK-1 plane and show typical inline motor mount. One pic. text said Walter Mikron engine has stardet to oil. So I think that it is a piston bypassing oil burn.
 

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TFF

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I know of a NSU dealer in the US. Showroom, parts room, and all. I don’t think it will be there too much longer. It’s a time capsule. It’s just a general repair shop now. They use to have Lancia Fulvas in the back along with other cool stuff, and had a VW drop side they used parts getter with hand painted lettering from the 60s. Once the dad is gone, the last son will sell it all. Mostly junk new stuff in the back, but there is still some good stuff. About four cars left in the showroom. Sold one about 15 years ago. Not in a good neighborhood anymore. It’s probably time to drop buy again and see what’s up.
 

Martti Mattila

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No wiseman would start this and stupid cant pull it tru so where I am. Definetly a masokist but what else. But it was this German guyi who made it at first in sixties, he end up bying LOM engine and designed a doppeldekker arround it. Grassmuckke was the name of that plane. I just thought that I can do better than this gentleman in Germany from NSU.
About the spare parts in that U.S. NSU dealer, my advise is to put them for sale in ebay. Now there is a small money to make from those parts, ten times more that scrap metal man pays. My problem is that I cot exited about new projects and when it is 95% phase I lost my interest because I can see it was doable. But I do have finished projects too when some outsider is ordering it or I prag to someone that I will do this and that. One thing I´m sure, nothing is so expensive than to be a poor and save the money doing it by my self.
 

TFF

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I get it. New projects are exciting and old ones are work. I have a friend who can complete stuff. He goes up and down, but gets them finished. He also can let go of them. He enjoys them and then it’s time to go. He built four airplanes and owned multiple others and doesn’t own one now. It’s the most amazing thing.
 

Martti Mattila

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"New projects are exiting and old ones are work." I will use that frase nex week when one team comes to see my my doings. Thanks.
 
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