Help with rupps jack shafts
- Thread starter Mtpckts
- Start date
Rupp jack shafts are readily available from Blackwidow motorsports. and they are not expensive. i don't see the advantage of re-designing it, or making it from stronger material. jackshafts don't break. and the newer design from BW is threaded, which is better than the roll pin design. just get that.
if you want to make jackshafts there are other brands you could do. for example Speedway. They used the same length/diameter jackshaft for all models (5/8" by 7.5".) The community in general would probably be better served making that jackshaft, as it is unavailable. But again it doesn't need to be special steel. They don't break or wear. they just get rusted out because the bikes are left outside in the weather.
if you want to make jackshafts there are other brands you could do. for example Speedway. They used the same length/diameter jackshaft for all models (5/8" by 7.5".) The community in general would probably be better served making that jackshaft, as it is unavailable. But again it doesn't need to be special steel. They don't break or wear. they just get rusted out because the bikes are left outside in the weather.
I personally believe that all jackshafts should use a 5/8-18 threaded ends and utilize a bearing "crush" spacer to pinch al the components together.
This way the drive sprocket, driven pulley or brake drum's keyway gets minimal torsional load applied and doesn't pound out the keyway over time.
Has anyone attempted to cut threads on a 5/8" 3/16 keyway shaft using a 5/8-18 die before?
This way the drive sprocket, driven pulley or brake drum's keyway gets minimal torsional load applied and doesn't pound out the keyway over time.
Has anyone attempted to cut threads on a 5/8" 3/16 keyway shaft using a 5/8-18 die before?
yes i have put 5/8-18 threads on jackshaft ends and use 5/8 nut. but it's not the preferred method in my eye. i like center drilling and tap 5/16-24 and use a bolt/washer instead. Though i like the large nut on the end of the jackshaft (that's how rupp does it for example), the 5/16 bolt has less protrusion at the end of the jackshaft. and therefore less crap to rub on my foot! on Rupps this is not an issue, and the 5/8 nut is fine, as the torque converter cover hides the nut. but on speedways for example it's a huge deal, and the 5/16 bolt is better.
as for the 'crush' idea, if the jackshaft is the right length, this is a non-issue. also with the 5/8 nut, most people over-tighten the nut, and screw up the whole system. also if the nut is rubbing on your foot, it can come loose (even though it is a nylon lock nut style.) And tear up your shoe! i just don't like the nut idea if the end of the jackshaft is exposed.
if you really want the 'crush' idea on a jackshaft that is drilled for a 5/16" bolt, you can use a 5/8 diameter washer on the end of the jackshaft on one side. personally i just make sure the jackshaft is the right length, but you can do it that way too if the jackshaft is a bit too long, and you don't want to dial in the jackshaft length.
but the one thing i'm sure we can all agree on, the roll-pin idea on a jackshaft is no good...
as for the 'crush' idea, if the jackshaft is the right length, this is a non-issue. also with the 5/8 nut, most people over-tighten the nut, and screw up the whole system. also if the nut is rubbing on your foot, it can come loose (even though it is a nylon lock nut style.) And tear up your shoe! i just don't like the nut idea if the end of the jackshaft is exposed.
if you really want the 'crush' idea on a jackshaft that is drilled for a 5/16" bolt, you can use a 5/8 diameter washer on the end of the jackshaft on one side. personally i just make sure the jackshaft is the right length, but you can do it that way too if the jackshaft is a bit too long, and you don't want to dial in the jackshaft length.
but the one thing i'm sure we can all agree on, the roll-pin idea on a jackshaft is no good...
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as 4340 is a high-strength, heat-treated alloy steel known for its toughness and strength-to-weight ratio. This makes it ideal for use in high-stress applications such as jackshafts.
To make the jackshafts even stronger, you may consider using larger diameter shafts or making them with a thicker cross-section. Additionally, you can use better quality bearings that are rated for higher loads and have a longer service life.
i'm just not sure why a stronger jackshaft is needed. i've never seen a broken jackshaft on any mini bike. and going to larger jackshaft size messes up a lot of other things like the jackshaft gear and the torque converter (not to mention the bearings.) the standard is 5/8". you go outside that standard, and things get complicated. this is the classic, "juice not worth the squeeze", situation.
