Best and most cost effective way of securing a small V pulley to a splined shaft
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    Question Best and most cost effective way of securing a small V pulley to a splined shaft

    Hello; first off, I'm new here so I apologize if I'm not supposed to ask a question first. I'm new to the machining world.

    I'm wanting to get your thoughts/opinions on how I could go about either making an adapter, or just making a custom pulley from scratch to secure a small OD 4L size V belt pulley to a 9 tooth odd-ball spline starter motor shaft that is 11.75mm in diameter.

    The pulley must be able to be secured to the shaft in a way that prevents the pulley from just sliding off the shaft, as the motor will be mounted so the shaft end points towards the ground. Also, I would prefer it if the motor shaft doesn't need to be modified in any way, as that is a stock part that I don't want to modify.

    I've found no readily available adapters or parts to do what I want, but maybe some of you know of off the shelf items, which is always a plus! The pulley OD I'm wanting to use is very small, about 1.55" approximately, as this will be turning a larger pulley via belt later on for more torque.

    I appreciate any help offered! Thank you

    Some pics below of the motor:


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    grub screw

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    Quote Originally Posted by jdaisy View Post
    grub screw
    You really think a little grub screw can withstand the torque? Not much of a surface area either for the grub screw to grab a hold of; it's splined

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    Damn,nice photo presentation.Welcome to PM.

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    The motor output shaft is not splined. It has pinion gear teeth, meant to drive a larger diameter gear. You could identify the tooth configuration and buy a mating gear of the needed size for your drive.

    It is hard to precisely measure the outside diameter of a nine tooth pinion. The caliper is not correctly measuring the gear diameter. The simplest way is to use a lathe and bore a hole, carefully enlarging it until it just fits the pinion. Then you can make a pulley with that size bore and use a set screw to lock the pulley to the gear. A standard set screw will damage the gear teeth, but there are ways to prevent damage if that is important. A pointed screw engaging the space between two gear teeth will transmit all the torque that the motor can provide, and probably more than a 4L belt on a small pulley can transmit.

    Larry

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    What is the size of the boss on the pulley. If there is enough meat you could put a longer grub screw that would go between the teeth/splines. I cant see it well enough but it looks like a gear rather than a spline.

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    Bore the pulley for an interference fit on the OD of the gear, drill and tap for 3 screws @ 120 degrees apart and use pointed sets crews in the roots of 3 teeth. Heat it up, shrink it on, tighten screws.

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    Quote Originally Posted by manualmachinist View Post
    Bore the pulley for an interference fit on the OD of the gear, drill and tap for 3 screws @ 120 degrees apart and use pointed sets crews in the roots of 3 teeth. Heat it up, shrink it on, tighten screws.
    Exactly the kind of answer I was looking for. Are we talking about dog point set screws?

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    Use a roll pin

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    broach it with a old motor shaft.

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    Quote Originally Posted by vettepicking View Post
    broach it with a old motor shaft.
    This is a cool idea too, as these motors are dirt cheap. Would the end of the old motor shaft need to be tapered like a real broach?

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    Quote Originally Posted by troop231 View Post
    Exactly the kind of answer I was looking for. Are we talking about dog point set screws?
    Never heard of a grub screw.Is it the same as a set screw or a socket head set screw ? I have heard of a half a dozen different point configurations too.But grub screw I never have heard.

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    Quote Originally Posted by jrmach View Post
    Never heard of a grub screw.Is it the same as a set screw or a socket head set screw ? I have heard of a half a dozen different point configurations too.But grub screw I never have heard.
    Could someone tell me what the best point style of set screw would be best for securing to the shaft as far as putting the most pressure on the 2 contact points? At first I was thinking cone point set screws, but now I'm doubting myself, as the point shouldn't bottom out before the taper of the cone pushes against the 2 contact points between the teeth. I like the 3 set screw at 120º opposed idea and heating pulley up first. Close up pic of shaft:


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    But grub screw I never have heard
    two empires separated by a common language!

    There are a number of us on here that would encourage you to acquire a shaper or slotter, and make the internal teeth/spline needed Or a tool and cutter grinder, so you can grind a wobble broach or make a spare motor shaft into a wobble broach with 1.5° back taper...

    Serioulsy,though; it really is overkill for the torque you can transmit. Is a 4L belt even rated for a 1.5" dia sheave??? That's a PD of what, maybe 1"?

    smt

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    i did this recently. i just epoxied the pulley on the gear. you can always get it off with heat.

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    Thank you for all of the thoughts, definitely good different strategies here mentioned.

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    " . . . as this will be turning a larger pulley via belt later on for more torque."

    Just to point out what's hinted above -- the wrap of a 4L belt on a 1.5" or so pulley won't transmit much torque; and there is little you can do downstream (e.g. the larger pulley) to increase it. Add belt tension to compensate; and bearing life could be an issue.

    Could be fitting a ribbed or toothed pulley and belt might do better?

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    Quote Originally Posted by PeteM View Post
    " . . . as this will be turning a larger pulley via belt later on for more torque."

    Just to point out what's hinted above -- the wrap of a 4L belt on a 1.5" or so pulley won't transmit much torque; and there is little you can do downstream (e.g. the larger pulley) to increase it. Add belt tension to compensate; and bearing life could be an issue.

    Could be fitting a ribbed or toothed pulley and belt might do better?
    Hi, this design needs to slip if need to, as it's cranking over a small ~150cc engine briefly for starting.

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    Are the bearrings continous duty?

    Once added pully to generator and converted to motor to have electric start on non electric start motor that we added to gas air compressor

    Bearrings did not hold up to heavier load and should have

    If this is starter motor bearings and commutator may not last long

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    Quote Originally Posted by Tony Quiring View Post
    Are the bearrings continous duty?

    Once added pully to generator and converted to motor to have electric start on non electric start motor that we added to gas air compressor

    Bearrings did not hold up to heavier load and should have

    If this is starter motor bearings and commutator may not last long
    Sprag bearing down the line on the secondary pulley (on the engine) will prevent the motor from turning once the engine fires up.


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