BC GB500 32 pitch gears

Discussion in 'Propulsion' started by wdodge0912, Feb 19, 2019.

  1. wdodge0912

    wdodge0912 Well-Known Member

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    I'm trying to figure out what gears I need to swap over to a 32 pitch gear system on the BC GB500. I'm gonna take an educated guess that it comes with a 35t for the shaft, with the 14t pinion to get the 2.5 ratio. I probably would need something closer to a 1.1, but I also need to figure out the tooth count and gear size to do it, so the gears still mesh.

    from what i can find, a 35 tooth 48 pitch has an OD of .771", and the 14 has an OD of 0.333"

    being that BC says it can go down to a 12 and up to a 20 tooth for the pinion, that wouls allow from .292” to .458” for pinion OD. I'm guessing if i add those OD to the OD of the spur, I'd have a good range for total OD of the gear set, so from 1.063 to 1.229" doing more guesstimate math, if I wanted a 1:1 ratio, I would need 2 gears that the OD would be somewhere in between those, and from what I can find, a 16 tooth 32 pitch gear has an OD of 0.563", so that would put me at a total OD of 1.126" so within that range.

    If I'm wrong on all that, please let me know. i'm just loosley guessing here. but i figured if I can find what gear I need on both ends for a 1:1 ratio, I can go from there to figure out what gears i need when I know what ratio I am going with, and I would like to make sure my thought process is correct as well

    so please feel free to correct me if I'm wrong, as well as suggesting what tooth count I souhld get.
     
  2. SnipeHunter

    SnipeHunter Well-Known Member

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    1:1 really wastes the advantages of a gearbox. 2.5:1 is a pretty good starting point. (really anywhere in the 2:1 to 3:1 range is probably a good enough starting point, dont overthink it at this stage)

    In general I'd recommend putting a fairly large gear on prop shaft (28+ tooth) as it gives you more room to play with the ratio later. Specifically the Traxxas 1526 (28Tooth) has always worked well for me at lower power levels and it's a good/cheap/easy to get starting point. Find a set or two in the 10T to 20T range for the motor and then go test and adjust as necessary.

    Assuming you're using an ESC my general advice is get the gear ratio setup so that you're on speed running somewhere around 85ish% throttle and then use endpoint adjustment to dial in your speed from there as that gives you the ability to adjust speed up or down depending on the specific lake/water without having to adjust gears.

    For higher power setups that need stronger gears and other "non-standard" drive parts SDP-SI has a great selection of parts.
     
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  3. wdodge0912

    wdodge0912 Well-Known Member

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    i was thinking 2:1 would be what I aimed for. was just trying to figure out what 32 pitch gears to get., figured a 1:1 ratio would be a good start and then change them from there. But was my idea of comparing OD's correct to make sure they still mesh? I don't need to much power their either, running a 28 second ship with 1 prop. I was thinking one of them should be a cheap plastic gear that i keep several on hand. as a dedicated weak point, most likely the gear on the motor.
     
  4. SnipeHunter

    SnipeHunter Well-Known Member

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    That math should work out.

    If youre aiming for 2:1 why not start there?? Seems like you're just making more work for yourself.
     
  5. wdodge0912

    wdodge0912 Well-Known Member

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    I probably am. I guess just to find that center point and work out from there. instead of.just starting out at a 2:1 then checking the ODs if they would work.

    a 20 tooth and a 10 tooth would work..I guess that would have been easy. it's just at the bottom of that OD range too, the 1.063
     
  6. Panzer

    Panzer Iron Dog Shipwerks and CiderHaus

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    Or you can go with what comes with the stuff from BC until you are actually on the water doing speed/steering testing, at which point you have the option of adjusting the ESC with end points as well as the gears at that point.:):):)
     
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  7. absolutek

    absolutek -->> C T D <<--

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    Why would you need to switch out the gears from the BC gear box for 32pitch?
     
  8. Panzer

    Panzer Iron Dog Shipwerks and CiderHaus

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    Only thing i can think of is more torque so you got that Hole shot at start up so when every one runs away from him he can keep with them just long enough to empty the side mount into the opponents Hull;);)
     
  9. wdodge0912

    wdodge0912 Well-Known Member

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    32 pitch is stronger, as well as I have in storage a ton of 32 pitch gears.
     
  10. absolutek

    absolutek -->> C T D <<--

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    Pitch doesn't factor in the amount of torque (that would be gear ratio), but I can understand if you already have lots on hand and what comes with the gb500 doesn't quite work for you.
     
  11. Anvil_x

    Anvil_x Well-Known Member

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    Uh.... I've burned out 32P gears. the pitch of the teeth doesn't factor into torque. Wider pitch gears are tougher (like the ones used for offroad RC trucks), but a lot louder.

    I got the standard GB500 setup, and they work well. remember that prop size and prop pitch also play a role. from what I have seen, going with a large prop with a deep pitch combined with the 2.5:1 ratio will give great acceleration.

    My twin 1.75" 40 pitch props on a 2.5:1 ratio driven by 550 cans on a 6 volt system will, if allowed to drive at 100% power, nearly hydroplane a twenty pound boat.

    I'm running 1.25 40 pitch props with a 1.75:1 gear ratio out of the GB500s. it's not ideal, but better rudder travel/clearance was my driving concern because my boat maneuvered like a puking dog.

    My new boat will be running with a pair of 1.5" 40 pitch props driven by 2.5:1 with 550 cans. I have the rudder clearance to run these, which I consider pretty darn good for a class 5.5 while still allowing good rudder travel and thrust cone direction.

    If you want to experiment, I would suggest, as the others have, that you get the basic setup and just work from there. that's what I did, and it worked. I also had multiple prop sizes.
     
  12. absolutek

    absolutek -->> C T D <<--

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    Interesting, were they the plastic ones? I guess I must be blessed because I've never managed to strip gears (at least not in a boat), and I run only 48 pitch metal gears. Just to give some perspective, I've run ships from destroyers up to a +32lb battleship (POW). I've run over rocks with my props, and been rammed in the props, bad enough to bend a blade. I'm certainly not an expert, but I don't believe there is a necessary reason to run 32p gears (note I already acknowledged OP had plenty of 32p stock on hand, and there was nothing wrong with using them). You should not be striping gears 32p or 48p. If you are striping / burning out gears, perhaps there is something else wrong. Is the gear lash set correctly? Is there excess drag on the shaft(s) (ie too much geese, bent shaft, etc)? Are the gears aligned properly? Vibration?

    Maybe it is different for the guys running a ridiculously oversize prop (2.5"?) on a Bismark.
     
  13. thegeek

    thegeek Well-Known Member

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    I run 32 rather than 48. Gear engagement is greater. Crap caught in the teeth less of a issue, (I don't floss) . Teeth are bigger.
     
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  14. SnipeHunter

    SnipeHunter Well-Known Member

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    Agree with Senor Geek, prefer 32 over 48, either can work if you put the effort in. Bigger teeth can transmit more torque before they break (yes I've sheared teeth off even using 32 pitch gears) and are more damage tolerant in general as well as being slightly easier to set the mesh on since you can have a little more slop in your work. 48 gives you finer resolution of gear ratio but when coupled with an ESC and endpoint adjustment it really isn't that critical, that helped more back when everyone was running an H-Bridge throttle.
     
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  15. wdodge0912

    wdodge0912 Well-Known Member

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    i was just saying I have more 32 pitch gears than 48 pitch. in fact i just had to get some tools out of my tool box, and found a 5 pack of hardened steel 32 pitch gears. They are everywhere lol. they might be the newer mod 1 gears though, I would have to check.
     
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  16. thegeek

    thegeek Well-Known Member

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    One step farther on durability. Machined collar with double set screws. 10/32 1550686047433-1174418060.jpg
     
    Last edited: Feb 20, 2019
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  17. absolutek

    absolutek -->> C T D <<--

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    Sdp-si?
     
  18. thegeek

    thegeek Well-Known Member

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    HPI 24t 32p

    Custom aluminum collar by Carlo.
     
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  19. kgaigalas

    kgaigalas Well-Known Member

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    In one day I have seen two boats lose prop blades.
    I use some plastic gears so I strip a gear not brake a prop. (designated weak spot)
    Also our whole fleet uses 32 pitch (available spares)
     
  20. Anvil_x

    Anvil_x Well-Known Member

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    YOU GUESSED RIGHT!!!! the gears were knocked out of mesh. I think the motor was knocked loose or something. Should have seen the look of surprise pondside when I limped her in after the battle. both metal. both worn smooth. hilarious lesson learned.

    Actually, I just spacebrained. I dunno what pitch they are. whateveer BC stocks. doesn't matter, it was funny at the time and I learned the lesson.