Advice needed on Rapidor Saw

Not if you weld on the attachment for pulling. I'm beginning to wonder if I should have started this!

Henry

In message , Mike Whittome writes

Hope This Helps

It took me about two years to work out what ROFL meant...

I see what you are driving at, but I maintain that my fingers and the top link are in fact pulling down. If you hung a weight on the chain, would you say that gravity was pushing on the weight?

All the best

Pete

Ha Ha my origianl statement said "mechanical method" this rules out gravitational attraction magnetic effect etc lol but a good try!

Mike -

Its NBG if you don't know your TLAs ;-)

Regards, Tony

OK - next time I want to help my buddy out by towing his car, I will attach the rope to the back of his car & the front of mine, and push - right?

Regards, Tony

That should work bit difficult driving in reverse though :-)

Tony Jeffree, unusually misguided in this instance, writes ...............

Actually, Tony, if you think about it , it goes like this.

Let us assume (a) that the rope is tied around the axle of your buddies car in the good old fashioned way. Further (b) that the rope is tied to a hook on the back of your towing vehicle.

The hook of your vehicle is pushing the eye of the rope. The rope eye at the other end is pushing the axle. Thus your buddie's car is being pushed down the road. QED

The rope itself is in tension.

Many laugh at me, some sneer, whilst the polite ones just smile! :)

Mike

So it's pulling the eye at its end :-)

Cheers Tim

eye eye

-- Regards,

John Stevenson Nottingham, England.

An ingenious analysis.

No, it's pulling the bit of rope in the eye, which is of course pushing the car :)

Tim

Trust the fool to reverse physics again.

Reminds me of an exhibit on flight that I saw once at a theme park in the USA. The exhibit explained how a wing generates lift - the path the air has to follow ovet the top of the wing is longer than the path under the wing, so the airspeed is higher above the wing, causing its pressure to be lower than the air pressure below the wing, hence lift is generated by the difference in pressure. So far, so good.

The second part of the exhibit explained that a jet engine works by air being taken in at the inlet of the engine at a low speed, and the engine compresses the air and mixes mit with fuel, which ignites, forcing the air out of the back at a higher speed, hence generating thrust.

But wait a minute...from the aerofoil description, slow air in at the inlet, therefore high pressure, fast air out of the outlet, therefore low pressure. Net pressure difference means that the resultant force should be forwards, not backwards! So all of the world's jet aircraft have their engines on back to front!

Regards, Tony

Nice test question Tony.

All I can say is "Non Linear System". Since a jet engine creates large volumes of combustion products, the mass and volume of gas out is much greater than the mass and volume of gas in.

So the engine really does create thrust (phew) Now, back to my hacksaw........

Mike

I hope you remember that the next time you try to "push" a bird... ;-)

Regards, Tony

Speaking from experience and misty memory you can't push birds. Although I must admit some of the ones I've pulled in the past would do serious damage to the reduction gears on a Scammell winch.

I fondly remember one in my early courtship days who went by the name of Crane Driver.

I think this all stems from my Granddad, he told me "Never go out with loose women" so since that day I have always set forth with a pocket full of allen keys and a set of Bahco grips.............

-- Regards,

John Stevenson Nottingham, England.

Tony Jeffree writes further on this topic, and in so doing he helps me to make my case .....................

In deed, Tony, very good. The higher pressure below the wing is pushing up the aircraft.

You have to agree (well I hope you do) that thrust is push, within the terms of the current and enjoyable discussion.

Mike Crossfield has answered this point far better than I ever could in an adjacent posting.

Mike

ps, when we have finished here, perhaps we can start a whole new string (possibly off topic, dependant on your point of view) on whether the bung hole in a timber cask is animal, vegetable, mineral, or abstract. :) M

Hmmm. Actually, I don't think Mike quite got the full answer there - true the mass & volume out is greater than the mass & volume in, but the key thing is surely that the larger mass & volume is being forced out of the back of the engine, and accelerated, so there is an equal and opposite force acting on the engine in the forward direction (which is significantly bigger than any force that might result from pressure differences in the two airflows).

Regards, Tony