45 degree 4

[okjim]

In a design for a scraper that is to skive off flooring, such as linoleum, tile etc, I am trying to prove that a 45 degree angled blade is the best choice for wear and capability. The blade will be flat to the floor and the leading edge is 45 degrees. Does anyone know how I can prove this to be true? Calculations or any other means would be very helpful. Thanks
Jim

 

[vc66]

KENAT,

You're almost as cynical as I am.

V

 

[KENAT]

Hey, if I remember correctly I've been here longer than you, I'm way beyond your level.;-)

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[MikeHalloran]

Uh, jim, if your boss thinks that's what engineers are for,
....
you need to get a new boss.

Tomorrow.



Mike Halloran
Pembroke Pines, FL, USA

 

[IRstuff]

We know what the OP asked. Just because he wants justification, doesn't he can or should get it.

TTFN

FAQ731-376

 

[KENAT]

Alternative approach.

Try and find the truely optimum angle.

See how close 45 is to it.

Come up with some justification of why 45 is a reasonable approximation given other factors that can't easily be calculated or some such twaddle, or perhaps 45 is within X% of the theoretical ideal etc.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

 

[okjim]

If a 45 degree blade edge angle is not ideal, finding what is ideal would get me farther down this path. Also remember, 45 degrees does not have to be the best choice for blade angle, but a compromise between wear resistance and the blade's ability to do the work is.
This may muddy up the discussion but....
We all know that if the blade was 90 degrees it would not wear as much as the 45 degrees but the 90 would not lift the flooring. I think that line of thinking is why 45 degrees was chosen originally. (anything less than 45 would wear quicker too)

Thanks for the Archard Equation suggestion, I will see what I can do with it concerning the wear.

 

[rb1957]

if the design works, why does someone want you to prove that it's the "optimum" ? maybe there are service/customer problems ?? certainly, it doesn't sound very optimal.

 

[waross]

I like 30 degrees. There should be less pressure on the blade with less deflection and as a result, less wear. As the angle approaches horizontal, the cutting edge becomes more prone to bending and breaking.
I suggest that optimum service life between sharpening and repair may not be the same as optimum for best efficiency and least energy expended.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[HamishMcTavish]

So basically you've been asked to back-fit a justification for an existing design...

Why not just check out the competition, i googled "floor scraper concrete" and came up with

http://www.floor-equipment.com/

Ring them up and ask if you were to buy/rent how often you would have to change blades. Ask the operators of your equipment what sort of lifespan the blades have.

It may be there is no theoretical answer - how thick is the lino, is there more than one layer, what adhesive is used will surely all play a part. Older lino floors may have asbestos in them and may require you to apply special precautions to protect the operators.

Regards, HM

No more things should be presumed to exist than are absolutely necessary - William of Occam

 

[TVP45]

Hello,

I did this about two years ago in order to take a lot of tile/linoleum off plywood subfloor. I bought a commercial scraper blade and reground it by trial and error.

I found the angle varied with the hardness of the glue. Hard glue required an angle above 35 degrees, but much higher dug into the plywood. Soft glue loosened well with something close to 30 degrees or a tad less.

I worked with the bevel down and found I needed a slight crown on the bevel so that I could "rock" the point up and down to avoid plowing - more of a problem with low angles.

I wound up doing a little bit on concrete and found that something like 45 - 50 degrees worked well since it didn't come to a dead stop every time I hit a concrete bump.

I think that if I had to do it again, I'd have tried pouring liquid nitrogen on the floor first to make all the glue brittle.

 

[NomLaser]

Adhesives usually have a high shear strength rather than tensile strength. My first thought would be to go around 20-30 degrees to break the bond then it would still have enough force to pry the flooring upward.