# Rotary mower blade tip speed



## JERSEY (Sep 9, 2018)

I have been reading up on blade tip speed, rpm......

Seems ansi. Has a rule of 19000, but it was 21000 previously.

I recently turned up a Honda powered 21 inch to 3500, cutting decent, much better than the 2600 rpm it was....then I stumbled upon blade tip speed.

I've gotten real good at sharpening my blades, but I am looking for the next level improvement.

I's 19000 a guideline, or absolute limit?
At3600 rpm, a 21 mower exceeds that 19000.
Some guys run 3300.....but the higher engine speed helps in thick turf on these tiny 190/160 cc engines.

Let me hear some thoughts......I know alot of old timers like 3600 and I can see why.


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## g-man (Jun 15, 2017)

If I recall correctly the 19000 fpm is to prevent projectiles speeds being too high (rock hit by the tip of the blade). I do think higher is better since it has more energy to cut the leave blades. With thick or wet grass, it could slow the actual speed from the idle you are measuring at.


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## x Wild Bill x (Aug 17, 2018)

This may be getting into the area of semantics, but is the blade tip speed WOT with no load? And if that is the case, does your mower have the power to maintain 3600 rpm under a cutting load? I know ztr's and riders with big engines can maintain their no load RPM or close to it, but if your your Honda with a smaller engine bogs down to say 3400 rpm under load what is you blade tip speed? Basically what g-man said above.

I personally feel that if your blade tip speed drops while making a cut in grass to the ANSI standard of 19,000 fpm I would feel comfortable running that speed. Something to think about and play with. There are cheap tachometers / power meters on eBay you can permanently mount and watch your RPM's as you mow that will give you an idea. I like having one on my machine to track service hours as well as engine rpm, if it drops even 200 rpm's I know something is up.


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