How strong are track hub threads?
- Thread starter Hummina Shadeeba
- Start date
Chalo
100 TW
Epoxy won't make it harder to strip (because the adhesive is so much weaker than aluminum), but it will make it almost impossible to service or replace. Don't do it.
DanGT86
100 kW
I have never heard of a hub thread stripping either. What kind of torque do you plan on putting into it? I feel like you will likely lose traction or do a wheelie before you reach a torque max capable of damaging the threads.
Bike trials riders use the same thread interface on their cranks and they stomp on the pedal to jump gaps. If a 200lb person jumping abruptly onto the crank doesn't strip it then I dont think a motor will.
There are bolt torque calculators online and lots of equations for calculating ideal bolt torque based on the thread dimensions and material. You could calculate it if you wanted to. Or just try it and hope for the best. I also would not epoxy it.
Bike trials riders use the same thread interface on their cranks and they stomp on the pedal to jump gaps. If a 200lb person jumping abruptly onto the crank doesn't strip it then I dont think a motor will.
There are bolt torque calculators online and lots of equations for calculating ideal bolt torque based on the thread dimensions and material. You could calculate it if you wanted to. Or just try it and hope for the best. I also would not epoxy it.
PaPaSteve
10 kW
A typical track cog is made from a high strength steel.
Say this aluminum spider is made from 7075 aluminum ... it probably is half as strong as it's steel counterpart.
So ... yes ... it could possibly strip depending on the applied torque.
JB Weld epoxy is a trick I've used for years on my motorcycles to stop countershaft sprockets from rattling on the countershaft.
Sounds crazy but it saves the shaft from needless wear.
When it comes time to replace the sprocket a puller is used to apply a modest amount of pressure and then heat (250 ~ 300F ) is directed to the sprocket until it "pops" off.
Same technique could be used here.
Another trick I've done for exactly the same project you are doing is :
Once the sprocket is in place, drill a hole right at the thread line between the parts, spider and hub, slightly deeper then the thickness of the spider.
Drill size is numerical #31
Fill the hole with a 1/8" hardened pin. (Cut off shank of a 1/8" drill bit works fine).
Hole should be tight enough that it takes some tapping with a hammer.
I actually do three pins.
The spider would need to shear the pins to turn on the hub.
Solar electric / pedal hybrid in my avatar picture is an example of this technique being applied.
Say this aluminum spider is made from 7075 aluminum ... it probably is half as strong as it's steel counterpart.
So ... yes ... it could possibly strip depending on the applied torque.
JB Weld epoxy is a trick I've used for years on my motorcycles to stop countershaft sprockets from rattling on the countershaft.
Sounds crazy but it saves the shaft from needless wear.
When it comes time to replace the sprocket a puller is used to apply a modest amount of pressure and then heat (250 ~ 300F ) is directed to the sprocket until it "pops" off.
Same technique could be used here.
Another trick I've done for exactly the same project you are doing is :
Once the sprocket is in place, drill a hole right at the thread line between the parts, spider and hub, slightly deeper then the thickness of the spider.
Drill size is numerical #31
Fill the hole with a 1/8" hardened pin. (Cut off shank of a 1/8" drill bit works fine).
Hole should be tight enough that it takes some tapping with a hammer.
I actually do three pins.
The spider would need to shear the pins to turn on the hub.
Solar electric / pedal hybrid in my avatar picture is an example of this technique being applied.
PaPaSteve
10 kW
Considering that ebikes are known to break spokes on a regular basis I'll adjust my thoughts on "pinning" the spider to the hub.
Rather than using a hammer to tap in a solid pin ... thread the hole and use a small bolt or set screw instead.
Rather than using a hammer to tap in a solid pin ... thread the hole and use a small bolt or set screw instead.
DingusMcGee
100 kW
If you can thread on 2 of these adapters at once so they thread conformally— tight to each other and holes aligned— you will have about 2x threads employed.
A stronger option:
On a good steel hub the threads can take over 300 ft-lbs. to loosen the gear holding ring.
A steel hub:
https://www.bikeberry.com/products/bbr-tuning-non-free-wheel-heavy-duty-axle-kit
I have welded [to stop rotation] the cheap Dicta hubs of alloy steel instead of using some inferior alum spider.
You will need a sprocket with the F5 bolt pattern and a 2.12” centered hole.
A stronger option:
On a good steel hub the threads can take over 300 ft-lbs. to loosen the gear holding ring.
A steel hub:
https://www.bikeberry.com/products/bbr-tuning-non-free-wheel-heavy-duty-axle-kit
I have welded [to stop rotation] the cheap Dicta hubs of alloy steel instead of using some inferior alum spider.
You will need a sprocket with the F5 bolt pattern and a 2.12” centered hole.
Chalo
100 TW
DingusMcGee said:
I've never seen one of those that was made in or near the 21st century. "Good" being the sticking point.
Steel hubs that have been made since the 1980s all have one thing in common: they are specifically made to be as cheap as possible, with no other criteria. In my observation, they tend to be made from soft cruddy material, with poor threadform and inaccurate thread diameter. For this reason I've seen more trashed threads on steel hubs than on aluminum ones.
If I were making my own hub from scratch, I would consider using a strong but relatively free machining steel like AISI 1144, but I wouldn't consider using a commercial steel hub for its strength. The only reason I'd use a normal steel hub made anytime lately is if I wanted to weld stuff onto it.
DingusMcGee
100 kW
Chalo,
Blah, blah, blah ——- it seems you are all bike salesman and no experience in unique build requirements..and parts choices….. so be it. And how do you know what steel is used in these hubs?…? Do you have one in your hands — give a Rockwell C test?, measure threads with a gauge? Bolts it to milling table and check alignment, centering etc??
Re: the cheap steel hubs
Made for motorized bikes — get it??
These mentioned by me hold up. Thank good they are cheap and they bring me home while running a QS 3000 at 120 amp low geared on/off trail.
The rear DT Swiss 350 have failed, rear Shimano Deore XT et al failed. $$$$ lost walked as no pedaling to car with broken rear hub. They did not bring me home.
These hub were not designed for edirtbike loads and are somewhat hard to modify as to make ‘em stronger.
If I were making one, #1 choice AISI 4140
Perhaps for good feedback to the rest of us you could name some of these “inferior steel hubs”? Links to sales?
Blah, blah, blah ——- it seems you are all bike salesman and no experience in unique build requirements..and parts choices….. so be it. And how do you know what steel is used in these hubs?…? Do you have one in your hands — give a Rockwell C test?, measure threads with a gauge? Bolts it to milling table and check alignment, centering etc??
Re: the cheap steel hubs
Made for motorized bikes — get it??
These mentioned by me hold up. Thank good they are cheap and they bring me home while running a QS 3000 at 120 amp low geared on/off trail.
The rear DT Swiss 350 have failed, rear Shimano Deore XT et al failed. $$$$ lost walked as no pedaling to car with broken rear hub. They did not bring me home.
These hub were not designed for edirtbike loads and are somewhat hard to modify as to make ‘em stronger.
If I were making one, #1 choice AISI 4140
Perhaps for good feedback to the rest of us you could name some of these “inferior steel hubs”? Links to sales?
DingusMcGee
100 kW
Steels 1144 and 4140 are quite similar
See:
https://www.makeitfrom.com/compare/SAE-AISI-1144-G11440-Carbon-Steel/SAE-AISI-4140-SCM440-G41400-Cr-Mo-Steel
Thanks Chalo for mentioning 1144 steel
See:
https://www.makeitfrom.com/compare/SAE-AISI-1144-G11440-Carbon-Steel/SAE-AISI-4140-SCM440-G41400-Cr-Mo-Steel
Thanks Chalo for mentioning 1144 steel
Chalo
100 TW
DingusMcGee said:
1144 and 4140 are similar in terms of strength, but 1144 is more machinable. It's not a deal braking difference, but I like to make things as uncomplicated as I can when fabricating parts.
