Project Auto powered hacksaw so far....

[daleyd]

Thank you...

Anything above about 10Hz you should be fine, I would normally consider forced cooling if it's expected to be run below this for long periods, though the motor manufacturer may give some more info on this.

 

[Noods]

I'm not getting into an argument about it, but you are incorrect.

Physics, the laws of, ye cannae change...

I'm not getting into an argument about it, but you are incorrect.

Physics, the laws of, ye cannae change...

a quote for you..

A four-stroke engine (also known as four cycle) is an internal combustion (IC) enginein which the piston completes four separate strokes while turning a crankshaft. A strokerefers to the full travel of the piston along the cylinder, in either direction.

The piston in this instance is a hacksaw blade..

 

[armalites]

Yes and that only proves exactly what we are saying, the piston is the hack saw blade and it's range of motion is governed by the crank in this case the pulley the rod is connected to, changing the rod length only offets the movement in one direction it doesn't change the distance travelled

 

[Noods]

Yes t

Engine Stroking & Engine Boring: Component Stack-Up
Rod length or piston compression height (piston-pin location) do not affect the bore size or stroke length, and hence do not alter displacement. However, rod length and/or piston-pin location changes may be required after a change in stroke to properly locate the piston top in the block for a desired deck height clearance at Top Dead Center (TDC).

http://www.hotrod.com/how-to/engine/ccrp-9812-engine-boring-and-stroking-fundamentals/

Yes that's basically what I said.. If you read it!

 

[armalites]

No it's not, you said changing the rod length will affect the stroke, it won't. Nobody is arguing that rod length and piston height won't affect performance but one that is 100% is they will not affect the stroke

I am more than happy to learn and see a demonstration where changing rod length changes the length of the stroke.

 

[Crater Creator]

Changing the con rod length does not affect the stroke.
What it does is change the angle of the con rod around the 90 degrees BTDC and ATDC position - which would alter an engine's characteristics. Piston acceleration/deceleration is also changed. But the overall stroke is not changed whether the con rod is 4" long or 20 feet long.

 

[Noods]

Yes and that only proves exactly what we are saying, the piston is the hack saw blade and it's range of motion is governed by the crank in this case the pulley the rod is connected to, changing the rod length only offets the movement in one direction it doesn't change the distance travelled

Wrong.. If you change the connection position on the pulley it will affect the rpm and also the stroke to a degree! The connecting point should be viewed end on vie as the equivalent to a journal on a four or two stroke crank, the stroke of an engine is defined by the movement from Bdc to tdc it's a lateral movement.. If you lengthen the con rod it lengthens the stroke and vide versa if you shorten it.. Yes the comp ratio would change with it as I said earlier.. There's lots of combinations you can come up with to alter these parameters ..

I studied for 7 years for a MV technicians cert, some of which involved technical drawings we had to create to produce different scenarios..

Failing that I will happily give you my Sons tel number at Durham Uni where he's a Doctor of physics .. He will happily discuss it with you..

Anyway, when it runs I will put a video up and then see how many doubters reply.. Might be a while, due to work commitments but, it will happen.. X

 

[armalites]

Noods I think you are confusing two things here, the location of your rod on the pulley has everything to do with the stroke, that is correct. If you keep the location on the pulley exactly the same and then making the connecting rod longer it will not affect the stroke. There is no way your son as a doctor of physics will agree with you.

If your are talking about changing the effective length of the rod then will change the stroke but that is governed by the position on the pulley not the length of the rod.

 

[Noods]

TBF I think there's confusion here as to what some of you guys are using the term STROKE as opposed to the definition we were taught and practice..

What you guys I believe are saying is.. The position of the pin on the pulley will affect the distance between BDC and TDC which is correct I have no issue there.., it would on an engine, along with knifeing the cranks webs, help to create a difference in rpm..

My theory is.. I need no difference in speed, due to running an invertor .. So, your definition will, state how far the hacksaw travels from its nearest point to the pully and the furthest point away from it as it travels along its slide.. And yes lengthening the rod would not make any difference to this window of travel..

However, engine builders define the stroke of an engine to where it positions the piston in the bore which can be defined by the length of the con rod.. Which obv affects comp ratios etc..

I hope this helps as I can see where the confusion is here.. Mine and your definitions differ somewhat .. Debate is healthy though.. X

 

[armalites]

I sorry but you are completely wrong, the stroke is the distance the piston travels in half a revolution of the crank and rod length has nothing to do with that at all. Engine builders do not use the term STROKE to define the postion of the piston in the bore. That is just not true!
Not sure why you are treating like a debate, we are talking about maths and physics with absolute values not someones artistic impression of an engine

 

[dobbslc]

All I've got to say about it is.....​

WANKEL!

 

[Noods]

TBF I think there's confusion here as to what some of you guys are using the term STROKE as opposed to the definition we were taught and practice..

What you guys I believe are saying is.. The position of the pin on the pulley will affect the distance between BDC and TDC which is correct I have no issue there.., it would on an engine, along with knifeing the cranks webs, help to create a difference in rpm..

My theory is.. I need no difference in speed, due to running an invertor .. So, your definition will, state how far the hacksaw travels from its nearest point to the pully and the furthest point away from it as it travels along its slide.. And yes lengthening the rod would not make any difference to this window of travel..

However, engine builders define the stroke of an engine to where it positions the piston in the bore which can be defined by the length of the con rod.. Which obv affects comp ratios etc..

I hope this helps as I can see where the confusion is here.. Mine and your definitions differ somewhat .. Debate is healthy though.. X

 

[Noods]

All I've got to say about it is.....​

WANKEL!

The old NSU used to have those.. Now I think it's Mazda ?

 

[Gareth_16V]

However, engine builders define the stroke of an engine to where it positions the piston in the bore which can be defined by the length of the con rod.. Which obv affects comp ratios etc..

I hope this helps as I can see where the confusion is here.. Mine and your definitions differ somewhat .. Debate is healthy though.. X

That's not stroke, it's deck height and squish clearance.

 

[dobbslc]

Yep and the Suzuki RE5, Norton's, Mazda RX8,
Not a con rod to be seen!

 

[brewdexta]

There's also the car named after a nasty itchy disease, the NSU Ro80

 

[brightspark]

its got 2 chances. it will work or it wont. all that will be lost is some time .providing u have the basic measurements ect which he has it can be improved upon as u go along the only thing I would sugest at the mo is fit a countershaft with a large pulley on it and reduce the speed down to saw so the motor doesn't have to run slow . it wont be happy if it does . edit thinking about it the kenedy hacksaw has an 8 inch pulley on the saw and a 2 inch pulley on the motor belt driven

 

[RichardM]

fan - if running the motor slow is a good idea, I have fitted a 12v computer fan to my mill motor as it started to melt some of the plastic insulation one day

 

[rory1]

If you find you are only using or wearing out the front or back half of the blade then pack out your workpiece with a block, ( or move your vice if you can) and then you can use the other half of the blade.