Oddball engines and prototypes

[WilDun]

Willy, you brought back memories.

Yes Ken,
Bet you were really enjoying the moment when that photo was taken, looks like it was near the max angle for lean! - It was a lethal machine (H1A) but bloody exciting at the time!

In those days narrow powerbands and 6 speeds were considered to be state of the art! - I remember I was trying to buy a little RM 80 for my kid and the guy who was selling it told me that it had a 'power band' as well - he wasn't exactly sure what that was, but he obviously considered it a plus!

I never owned an H1 but had a ride on one - I was riding a Suzuki T20 on the road (and on the track as well - every man and his dog raced one of those) - it was almost as diabolical to ride (only smaller) ie narrow powerband and handled like a wet sausage and when you braked hard, the forks didn't work because they were so skinny they used to flex and cause all sorts of chatter! - the chatter wasn't so bad after the first lap when the front drum brake had lost a lot of it's effectivness!!
Everything became worse when I tweaked the engine - but if you weren't scared, and let it do it's thing, it was a lot of fun and still capable of blowing off the big Beezas, Nortons and Triumphs on our short street circuits - I loved it!

Now I've got to stop dreaming, get out of my chair, go out into the garage and try and make something - hard to do these days, but I'll be ok when I get out there! - I think

[Frits Overmars]

Willy, you brought back memories. Here's me on one of the first H1s in Melbourne, racing it at Winton in around 1972. Poor handling reputation was surpassed by the drum brake. Later I made up a set of expansion chambers based on Gordon Jennings articles in Cycle World magazine.

It brought back memories for me too. As the proud owner of a Kawa H2 I must of course start by saying that the H1 was for sissies, but I will admit that the H2 had a much stiffer frame. And after lightening the cylinders by way of a little grinding, replacing the standard carbs with a trio of 38 mm Mikunis and the standard pipes with some gizmos of my own I also felt the need to fit a second front disc brake and clip-on handlebars. It made the bike even front-heavier than it already was but from 3000 rpm onward I could control the extent of my wheelies with my right hand; no clutch required (to be honest, the wheelying had to be done from one petrol station to the next )

I had been preparing a couple of Suzuki T500 racers for some friends and on my H2 I used to watch them through the corners and show them the way on the straights. Ahh, those were the days.

[WilDun]

It brought back memories for me too. As the proud owner of a Kawa H2 I must of course start by saying that the H1 was for sissies,

My most vivid memory of the H2 was of a guy going round the bottom loop at Pukekohe, highsiding it and gliding gracefully through the air at high altitude, (only thing that spoiled it was the great thump at the end!).

If the H1A was for sissies, then I'd better not talk too much about my Suzuki T20.

[Frits Overmars]

If the H1A was for sissies, then I'd better not talk too much about my Suzuki T20.

The H1A's lack of handling and braking was more demanding than the H2's power, I'll grant you that .

[WilDun]

The H1A's lack of handling and braking was more demanding than the H2's power, I'll grant you that .

From memory, they tamed everything down in the later versions of the H1 but they just couldn't compete with the (RD 400?) Yamaha twins.

[WilDun]

I came across this new "breakthrough" in engine design. Of course it has it's merits but it sure 'aint no breakthrough' as far as the mechanism is involved!

http://www.fishertechnologies.net/index.php
http://www.fishertechnologies.net/howItWorks.php

The same basic idea was used on shaping machines from the year dot! It was used in shapers mainly as a simple way to save time on the non working return stroke.
Also it could be ajusted for stroke by undoing a nut and moving it in a slot on the crank wheel (moves the crankpin relative to the crankshaft) - Beats me why that system wasn't used on hacksaws as well!

https://www.youtube.com/watch?v=Jx5nOn0tf_k
This is a detailed description by Tubal Cain (good guy). definitely worth a look if you've got the time!

I have seen many "breakthroughs" in my time - I can remember the Suzuki T500 coming on the market in around 1970 in the US and being hailed as " The world's first dual cycle twin" - (dual cycle? - what the hell is that?) - Scott, whose two stroke twins were 'yowling' their way through the countryside more than 50 years previously would have turned in his grave to have heard that line!

[WilDun]

I should have mentioned that I thought Flettner was using the same basic concept when toying with a beam type engine with a "straight line" piston idea (except that the pivot end of the beam was allowed to 'float' by way of a pivoted rod).

Am I right Flettner, or have I strayed from reality.... again?

[Frits Overmars]

From memory, they tamed everything down in the later versions of the H1 but they just couldn't compete with the (RD 400?) Yamaha twins.

Riding the Kawa H2 was hard labour, only rewarded by the fact that I could zap everything else on the road.
I also used to own a Yamaha RD350. Riding that was pure joy, even if the Kawa was 50 km/h faster in a straight line.

[F5 Dave]

My 350B wasn't a joy. Someone had mounted the size up tyres and it didn't turn with any urgency.

It also oiled the rhs plug with monotonous regularity. I changed the crank seal twice but I was told by the parts guy I could lever the old one out, file off the outer ring and push the new one in, as I was 17 and too dumb to split the cases. Or learn from my first mistake as it seems.

Probably a good thing, might have stopped me having a worse crash on it than I did after a mate helped me bleed the brakes.

Had the obligatory 250 stickers over the 350 ones.

[Niels Abildgaard]

Please help me.

I have had a BMW R25/3 and drove 45000 km ,a BMW R50S drove 2000 and bent it,a R27 and drove 70000,a BMW R96S but could not afford it and sold it very shortly after in 1975.

In 1995 I got a MZ251 with a turkish 300 ccm engine and drove it 80000 km on two sparkplugs and two chains plus tires ,petrol and oil.It stopped once unwanted in pouring rain.After a silcone spray on HT lead no more problems and I rode sumer and winter ,wet and dry.

It was by far the best bike I have met.
It is sold as I am 70 and is pulling a sidecar somewhere.On a like scale from 1 to 10 it scored higher than family.

Only thing is I feel engine would have been even better made as drawing.

My question is:
Please help making a formulae for exhaust valve diameters versus RPM( fourstroke) and what is basecirkel diameter of the OHC.
This based on present OHC engines
If such a formula can be made the 120 years of fourstroke plaque has not been totally in wain.

[tjbw]

Please help me.

...

My question is:
Please help making a formulae for exhaust valve diameters versus RPM( fourstroke)

...

Sorry I don't have a RPM formula, but I guess it would include the number, and size, of exhaust and inlet valves per cylinder, bore/stroke ratio, type of valve actuation, and more.

Anymore images of the uniflow sidevalve engine?

[Niels Abildgaard]

Hello tjbw.
I can make any picture of anything as it is only a computermodel,so what do You want?
I have made a V2 90 degree two stroke Ducatti beater.

http://i.imgur.com/kgeUWsJ.jpg

To be realistic I need a rough idea of what present ,real valve trains, fourstroke engineers have made to work.As You can see the crankshaft actuated valve works more or less like an overhead camshaft valve from a fourstroke.
What is the size of a F1 exhaust valve and how many rpm can it do before floating?
How big is an exhaust valve of a state of art 4 cylinder 600 ccm and what rpm can it do before floating?
I have some numbers for a VFR 750 anno 1988. 8 exhaust valves of 23 mm dia allowed 105 horses to pass.Each valve of 4 square centimeter took care of 13 horses, that is roughly 3 horses per square centimeter.This was at 10500 crankshaft rpm and redline has probably been at 12000.
This means a 23 mm valve took care 13 horse and could at least operate at 100 rps or 6000 rpm two strokewise.
The Aprillia 125 ccm people achived 17 bar as mean effective pressure due to very efficient exhaust system tuning.
My Mz ran 7.5 bar all day rain or sun.
7.5 bar at 100 rps means a cylinder of 130 ccm and 55 times 55 mm is nice to look at and give a mean piston speed of 11 meter per second.
A 13 horsepower machine for all eternity if the valve can be persuaded to obey crankshaft.

[Grumph]

One limiting factor in the valve train you propose is the weight of the parts and the accelerations you're asking it to perform.
You need to speak to a cam grinder. I have no idea if there are any local to you, but local to me here in NZ there are at least two who have analysis software. They can tell me if I'm trying to exceed known limits and what sort of spring pressure I'm going to need with that profile.
Base circle problems - and inevitably you'll have a base circle bigger than you'd really want - can be dealt with. Roller followers come to mind.
I have to say that the valve area as proposed looks to be a major limiting factor too...The layout is effectively a sidevalve. Due to the odd shape of the chamber and the need to maintain some sort of compression, the chamber wall will limit the effective area of the valve to around half the circumference.

[tjbw]

Hello tjbw.
I can make any picture of anything as it is only a computermodel,so what do You want?
I have made a V2 90 degree two stroke Ducatti beater.

http://i.imgur.com/kgeUWsJ.jpg

To be realistic I need a rough idea of what present ,real valve trains, fourstroke engineers have made to work.As You can see the crankshaft actuated valve works more or less like an overhead camshaft valve from a fourstroke.
What is the size of a F1 exhaust valve and how many rpm can it do before floating?
How big is an exhaust valve of a state of art 4 cylinder 600 ccm and what rpm can it do before floating?
I have some numbers for a VFR 750 anno 1988. 8 exhaust valves of 23 mm dia allowed 105 horses to pass.Each valve of 4 square centimeter took care of 13 horses, that is roughly 3 horses per square centimeter.This was at 10500 crankshaft rpm and redline has probably been at 12000.
This means a 23 mm valve took care 13 horse and could at least operate at 100 rps or 6000 rpm two strokewise.
The Aprillia 125 ccm people achived 17 bar as mean effective pressure due to very efficient exhaust system tuning.
My Mz ran 7.5 bar all day rain or sun.
7.5 bar at 100 rps means a cylinder of 130 ccm and 55 times 55 mm is nice to look at and give a mean piston speed of 11 meter per second.
A 13 horsepower machine for all eternity if the valve can be persuaded to obey crankshaft.

I would be interested to see a cross section of the combustion chamber, also inlet and transfer ports.

Your V twin has a nice simple exhaust valve. That configuration is called side valve, and the side valve engines are also called flat head engines.

Side valves were outperformed by overhead valves, which were then outperformed by overhead cam designs.

Some F1 engines can rev to more than 20,000 RPM, they use pneumatic valve springs and overhead cams, however current regulations limit maximum revs to 15,000 RPM.

For your engine I think you should go for the largest valve area you can get, and the maximum valve lift, with whatever compression ratio you want to run the engine at.

I've read elsewhere that poppet valves don't open fast enough to create the exhaust wave action that is utilised by high performance two-stroke engines.

If you want a high power Ducati beater I suggest you consider alternatives to the side valve. Honda have recently patented a uniflow two-stroke with overhead poppet exhaust valve, but I wouldn't expect that to be a Ducati beater either.

[ken seeber]

Niels, I must say that I just love the finning on these MZs. Beautiful raw simplicity. I had a Jawa 250 Californian for a while, that was similar, but no big fins though.

As a digression, have a look at this: https://www.youtube.com/user/RaceEngineTechnology.

Not much in common with bikes, other than the skinny front wheels