Wonderful things, flywheels.

Hello Guest,

As PWSlack has stated.

You can test this by removing the flywheel.

The engine will not run.

Kind Regards....

Pull the flywheel off of any engine and it will not run regardless of the number of cylinders. This obviously excludes any that do not use one. I only say this because some where there might be one that does not use a flywheel. Have not seen it though.

If you really want to have fun, take the blade off of your neighbors push mower. It wont run either. He will pull the rope until he gets fed up and pushes it to the curb. You take it home and put the blade on it and start mowing. This should get a really dumb founded look. Be sure to give it back after the prank. Most push mowers use the blade as a flywheel. Older models had cast iron flywheels and would run without the blade. The new ones have light weight aluminum flywheels and need the blade to run.

The Mechanic

Sorry for not logging in.

Working at a different terminal and forgot password.

You will just have to be our guest then.

I am not sure but this little beast might fill the bill.

http://en.wikipedia.org/wiki/Delta_engine

I first came across them in mine sweepers as they have a high power to weight ratio, therefore less draft on the vessel, less chance of contact with a contact mine. The block was made of aluminium alloy so it also had a small magnetic signature. All this is very reassuring when you are in the engine room on active mine counter measure duties.

I never got the chance to pull one down as we never had any problems with them.

BAB

This is why I love this site. I learn something every day. Very interesting engine design. Before reading the article the first thing that came to mind when I saw 2 pistons on one crank was my Puch SGS 250 Twingle. I am now wondering if the Puch design was a take off of the Delta.

Pull the flywheel off of any engine and it will not run

Lets be careful what we say Guest..............that statement is incorrect............have you ever worked on a Napier Deltic diesel engine.........sorry, that was a silly question.......obviously not........because Napier Deltic diesels do not have a flywheel.

Basically they are a two stroke engine with a triangular configuration, they have opposed pistons and 3 crankshafts and 3 cylinders/bank. Usually in main propulsion or traction engines they have 6 banks = 18 cylinders = 1 power stroke every 20⁰ of crankshaft rotation, therefore no flywheel required.

Bear in mind that the flywheel is used to store energy from one power stroke to the next and assist in the smoother running of the engine. Generally speaking the greater the number of cylinders an engine has, the smaller the mass of the flywheel.

Thi is a scematic section of the Napier Deltic diesel engine.

Pull the flywheel off of any engine and it will not run

Lets be careful what we say Guest

Hello MOBI, I was trying to be careful in what I said. The next sentence states "This obviously excludes any that do not use one."

Never claimed to know all of the types of engines made, thus the disclaimer. Just passing on what I know and stand behind the original claim of removing a flywheel from an engine that is supposed to have one it will not run. I will submit to a slight change in that it may run but not very well. Are you saying that an engine that is designed to have a flywheel will work just fine without it? My first experience in changing out flywheels was converting a push mower engine over to run an 8 roller chemical pump. I was building a spot sprayer for apple trees. Like to have broke my wrist when the motor kicked against the pull rope.

Hi The Mechanic,

...........oops.............that will teach me for not reading your comment correctly.

My apologies.............I suffer from foot and mouth disease...........whenever I open my mouth I put my foot in it..............it's now spreading to the written word.

No worries mate.

No apologies needed.

Sometimes what I think I write and what it actually reads are 2 very different things.

Must be that special form of dyslexia where the words just don't come out right.

Probably put it down to temporary insanity.............no..............just insanity.

It's those sane ones you need to watch out for.

That's that disease you catch from your kids, isn't it?

My kids aren't too bad it's the grand kids..................I made a big mistake............my wife wanted me to build a granny flat..........I agreed, in a moment of tempory insanity.

I have 9 grand childeren............fortunately only 3 of them reside here. but when they all come...............I get into trouble, my wife thinks that I am a big bad ogre.

That's because I wont let the kids "destroy" everything.

A flywheel increases its energy with the square of speed, so fast engines in which low speed idle is not important can have small flywheels. Some racing two strokes have essentially no external flywheel weight, with the crankshaft serving as the flywheel.

Big old motorcycles were infamous for darn near breaking the legs of riders who tried to start them with an insufficiently hard kick. When the spark occurred (at perhaps 20 degrees BTDC) the piston would quickly decelerate and be forced back down the cylinder before making it over center -- causing the kick starter to kick back.

While rambling here... Also, many two stroke single motorcycles could be started in reverse if the kick was not quite energetic enough. The same scenario as described above would occur, but the two stroke would continue to run in reverse.

I had one of those old knuckle heads, with a tank shifter, suicide clutch, complete with leg breaker crank and reversed hand crank spark advance control on the right and throttle twist control on the left. Really screwed the Harley riders up big time. It was a 1946 Indian Chief. The original owner didn't make it home alive from Korea. A friend of mine bought it and couldn't handle it. I bought it for $200.00 in 1963. It still had the remnants of the leather saddle bags under the chrome retaining straps on the rear fender. It remained in a barn in Bucks County Pa. from the time the original owner got drafted for the war until 63 when my friend bought it. I got it with 6134 miles on it. I wonder what it would be valued at to day? DUM DUM DUM!!!

Sure wish I hadn't traded it for a boat, motor and trailer. Darn boat sunk. Gave it to my uncle. Blame on being young and foolish.

Have a nice holiday.

TMF

Funny, in exactly that year, I had an Indian 30.50 Sport Scout (and part of another, which was a 45). Yeah, the reversed throttle and advance were interesting -- and I think one was reversed not just from side to side, but in rotation direction. (Although Indian would say Harley had is reversed, I suppose.) If I recall, with my brother's Harley (I rode his flathead 74 a lot when I was 12 and 13 -- I was a scrawny kid, and had to be sure I didn't let it lean too far while stopped) you rolled both handles back as you accelerated, but with the Indian, you rolled one back, and the other forward. The Harley was a '47, and one of my Indians was a 43 -- the other unknown, but a little newer, I think.

I sold just the front fork from the Indian for substantially more than I paid for the whole bike (which was $15 in a basket, -- the Harley was $75, also in a basket, and with a completely scattered motor -- hundreds of piston pieces in the crankcase) I can't remember what it took to get the Indian running (but I think almost nothing.) The Harley was running and looking pretty good with Cadillac Firemist red paint, for $250 total investment.

I'd love to have the Indian now. As I would several other vehicles I've had.

At one point, I bought a Citroen SM, which was this exotic, Maserati-powered hydraulic school on wheels. I paid $7300 (in 1976 or so, I think). At the same time I could have bought a Lamborghini Miura for $9,000. The $7300 was a stretch, and the $9,000 was just too much of a stretch. The Lambo today would be worth $300,000 -$400,000; the Cit, still not much over $7300. Argggghhh. But I suppose I wouldn't have survived the Lambo.

I hope your holiday is fun too.

Yep, you got it. The flywheel is the 'main man' here. The more mass in the flywheel the smoother it'll run.

Experiment for you: If you have a vertical shaft rotary lawnmower, the blade disc is part of the flywheel mass. Take it off and try to start it. It's possible that it'll start but it won't idle smoothly. Every compression will be felt.

The ACTUAL working member of an engine is the flywheel. It takes up energy,stores it, and imparts it to the work,as required, to be 'topped up' by the power processes to which it's harnessed and which keep it spinning.

In modern race engines the actual flywheel member is a very lightweight item indeed, aided in it's job by the addition of the mass of the crank itself (in itself very much lightened).

The sum of all of the items which form the primary rotating mass, are to be considered the 'flywheel' mass.

Hope this clarifies it some. I've purposely left some out as it, as you'll get to see, isn't as easy, nor simple, as some folks think, and to illucidate to your ultimate satisfaction will take more time than I have just now.

Come to my workshop and I'll show ya.

Cheers

Stu

The 'magic' here is as a result of the flywheel. The flywheel provides the energy of required to move through the idle strokes (from one power stroke to the next). If u try a fly wheel of a mass less than the minimum required mass, it will not complete the idle strokes.

Sprint cars (360 and 410 CID small block chevys) do NOT have a flywheel. They run just fine. Idle is 1200 RPM.

mobi--thank you thank you.while back i was researching engine configs to eliminate flywheel.turned up deads ends.that engine was cool.gonna go read up on it.as proved my search technique seems to be flawed so if you have a good source let me know please.

ken--how does the crankshaft serve flywheel purpose?thank you too.i had never paid attention to backkick phenomenon.now i know why it happens.any easy solutions to avoid knee implants??:)

Hi shanky,

I will see what I can find out for you.

Search the web under "napier deltic"............there is a reasonable amount of info there. If you require more let me know.