Billy Goat Contour update: Blade tip speed

Discussion in 'Lawn Mowing' started by Ngog_Nrythrng, Sep 23, 2003.

  1. Ngog_Nrythrng

    Ngog_Nrythrng LawnSite Member
    Posts: 73

    This spring I posted about a mistake I made: purchasing a Billy Goat Contour 24" high wheel mower.

    To try to get it to work better I decided to increase blade tip speed. The listed speed is 12180 fpm with a 5.5" pulley above the blade. I changed to a 4" pulley and a belt 3" shorter, which should raise bts to 16748 fps, assuming no decrease in engine rpm. It cuts much better, but certainly not well enough to recommend it.

    Should I go to a 3.5" pulley? How fast is safe? If there is no decrease in engine speed (not likely) bts would rise to 19140, but I would bet it would really be around 18000. :confused:
  2. FrankenScagMachines

    FrankenScagMachines LawnSite Platinum Member
    from IN
    Posts: 4,739

    What can it hurt to try? Most commercial mowers are 18-18500, 18500 being the maximum allowed for factory specs but alot of guys turn up RPM or change pulleys, so they would be higher than 18500. I say do it and if you don't like it take it back off right?
    You HAVE checked deck level right?
  3. Ngog_Nrythrng

    Ngog_Nrythrng LawnSite Member
    Posts: 73

    FrankenScagMachines, I am not sure what you mean by check deck level.
    It is level. Changing pulleys did not alter any other specs. ?
  4. Ngog_Nrythrng

    Ngog_Nrythrng LawnSite Member
    Posts: 73

    I installed the 3.5" pulley, and the cut with the regular blade is good. I can finally use second gear.

    The mulching blade still leaves an unacceptable cut. The deck is probably too shallow and the mulch blade ends up pushing the grass down.

    I tried a 52" belt, but it is too short. With the 3.5" pulley the 53" belt is too long. It works, but the deflection due to the tensioner pulley is too much: belt wear will be affected. I can't believe the difference between a 52" and 53" belt can be so much. I compared and installed each numerous times. Off the mower you can barely tell the difference, but installed it is amazing. I have looked for a 52.5" by 5/8" belt on the web, but no luck so far.

    If you are stuck with a BG Contour, do yourself a favor and change out the blade pulley with a 3.5". It makes a big difference.
  5. FrankenScagMachines

    FrankenScagMachines LawnSite Platinum Member
    from IN
    Posts: 4,739

    I know of some places locally with odd sized belts I will look around for you for a 5/8x52.5" belt. Email me so i have your email address then i can tell you if i find something.
  6. greasy_gun

    greasy_gun LawnSite Senior Member
    Posts: 334

    Hi guys...interesting deal, changing blade tip speed .

    How do you figure the blade tip speed?

    have an old simplicity rider i would like to play with?

    Thank u
  7. Doc Pete

    Doc Pete LawnSite Gold Member
    Posts: 3,469

    Sorry, I think you're a bit off base. Most mowers are under 18500. Those that are around 18500 are bigger 60/72" machines, and guy's aren't increasing them further.
    The main machine to speed up is the 48" WB. Furthermore, since I've been playing with speed ups on different machines, most of the WB's don't have enough horsepower to pull doubles and higher tip speed. And, guy's that "do" speed up their machines, without enough Horsepower, end up "below" the stock speed, as soon as they start mowing anything but very thin, light grass.
    In other words, unless you've got a lot of horsepower, "in operation", a speeded up machine will actually cut at a slower speed.
    Put it this way, as soon as you engage the blades on a 17/48 WB with double highlifts, the rpm will slow down, but you even start cutting grass.
    At the current time, the SWB (23/48) is the only WB that will turn around 19,000 tip speed with highlift doubles and hold it through most grass. Yes, it's been sped up, and I'll have full info tomorrow.
  8. FrankenScagMachines

    FrankenScagMachines LawnSite Platinum Member
    from IN
    Posts: 4,739

    Pete, as far as I know all eXmark w/b's are 18000-18500 FPM stock. i know most don't have power to turn alot faster but a freind has a 17/48 Hustler w/b and changed pulleys to increase speed and he said a math wiz friend of his told him what the final speed was, it was close to 18500 FPM. It has plenty of power and does a fine job. I do think once you got much over 18500 or 19000 you would start having problems on most machines.

    Just checked my 2003 eXmark catalog, all walk behinds (eXxcept Metro 21") have 18,500 blade tip speed eXcept the 36" Metro HP (belt drive floating deck). So I guess you're wrong, and the REAL commercial mowers do have at least 18,000 FPM BTS. I was right haha. check if you do not beleive me.
  9. Doc Pete

    Doc Pete LawnSite Gold Member
    Posts: 3,469

    OOPs, I forgot I'm trying to have a conversation with a Kid.....OK, so whatever you say is fine.... I'm wrong............
  10. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    Power has nothing to do with BTS. You can take a 21" walkbehind (push) mower and easily crank it well beyond the imaginary 19,000 FPM BTS. 60" Dixie Choppers come from the factory exceeding 20,000 FPM BTS. Figure it out for yourself.

    Dixie Chopper recommends 3750 engine RPM
    20.5" blade
    1 to 1 pulley ratio

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