Alpha blade tip speed???

BigRed150

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I have the Big Dog Alpha (aka Raptor). I think the blade tip speed is around 16k. What controls this speed? Is it the pulley connected to the blade engage unit. If so can you trade out the pulley for a Alpha Mp ( aka Raptor Sd) one and increase the speed.
 

BlazNT

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OK so lets discuss this:

Everything you have now was engineered to work at the speed it runs now. If you change things they will fail sooner. The biggest issue to me is the blades are not designed to go that fast either. You will have to upgrade they for safety reasons. That is unless you carry good insurance that covers you making safety changes to your lawn mower when the blades shatter and go everywhere if you hit something running at the higher speed.
 
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Carscw

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Warning WARNING WARNING
DO NOT pulley swap the deck.
The only thing you will accomplish is hurting your self or someone else.
The spindles and idler pulleys will not handle it.
Even if they could the engine would bog down in thick grass.
 

bertsmobile1

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And if it actually works and the blades spin a lot faster without blowing the spindle bearings then there is a phenomia called high energy deformation.
The faster the blades spin the easier they will twist & bend when they strike something like a rock or root or branch.
Also you end up with a massive grass throw butthat will want to leave the deck at a different position and may end up cloging or choking the discharge chute.
If it dosen't clog the chute it will do stuff like throw rocks 50 yards.
 

BigRed150

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Got it. I will not attempt to change the speed. Safety first.
 

BlazNT

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If it dosen't clog the chute it will do stuff like throw rocks 50 yards.

I love living in the Ozarks. Almost every rock is limestone. They just turn to powder when you hit them.
 

Mad Mackie

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Most ZTRs have engines that are setup for 3,300 RPM or 3,600 RPM at high idle (full throttle). 3,300 RPM appears to be an attempt to extend engine life verses 3,600 RPM engines, not sure if this has been effective.
Mowing must be performed at full throttle.
You can determine the blade tip speed fairly easily by checking the spindle pulley RPM at full throttle, PTO on, with a photo tachometer and the blade length. Photo tachs are plentiful and reasonably priced. If you have one or buy one, remove the battery when not in use. A small piece of reflective tape is stuck onto the pulley which reflects so the photo tach can work. Belt/pulley cover must be removed to expose a spindle pulley. a R/H or L/H pulley can be used to check RPM as you are seated on the running machine. Reinstall the cover after checking the pulley RPM.
The formula for determining the circumference of a circle is C(circumference) equals 3.1417(Pie) times the diameter(blade length in inches). This gives you the blade tip travel for one revolution, multiply this by the RPM of the spindle pulley and you will have the blade tip speed in inches per minute. Divide this by 12 and you will then have the blade tip speed in feet per minute.
You had commented about swapping pulleys to increase blade tip speed. Manufacturers change deck pulley sizes between different deck sizes to maintain but not exceed the maximum legal blade tip speed. As has been mentioned, this not a recommended. The Big Dog Alpha and the Alpha MP do not share the same size decks and may have several different spindle pulley combinations to achieve max allowable blade tip speed.
 
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Have_Blue

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I have the Big Dog Alpha (aka Raptor). I think the blade tip speed is around 16k. What controls this speed? Is it the pulley connected to the blade engage unit. If so can you trade out the pulley for a Alpha Mp ( aka Raptor Sd) one and increase the speed.

I've mowed at 14,000 FPM with great results, but I did have to keep the blades sharp.
 

RetiredGuns

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This is the 3rd season of mowing with my 42" Raptor. 18k BTS and 3200rpm seems fine for my 1/2 acre and not letting the grass get 6" tall. I was all caught up in BTS in the beginning, but it has been a non issue.
 
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