Design a Freewheel Crankset for Direct Mount Crankests

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ScooterMan101
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Design a Freewheel Crankset for Direct Mount Crankests

Post by ScooterMan101 » Sep 19, 2017 2:02 pm

Looking into Mid-Drives I see that the only option for a freewheel crankset currently available as I write this is the old fashion square taper bb or IS design .

However ...

Many of the bikes available now have , and more in the future will have Direct Mount Cranksets.

Evidently the BMX people are wondering why it has taken the 26 inch through 700c/29er bikes so long , to start using this three piece design since there are advantages.

Since most Good bikes in the future will have the Shimano Hollowtec II 2 piece design or what is looking like more likely , most will have 3 piece design / aka / Direct Mount Cranksets ,

Now is the time to design a freewheeling Crankset using the Direct Mount system.

The two people here in the U.S. who are doing the custom larger mid-drives do not know at this time how to design one, and the other person who is making a mid-drive here has said months ago he is looking into using Direct Mount Cranksets on his mid-drive , SamD ... but he has gone silent for a few months now, so I don't know, I question if he will ever get a Mid-drive available .

So I put forth here now, a Goal of getting the World Wide Members of Endless Sphere to come together and submit their design and Ideas.

With enough of us working on this we can come up with the solution .

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by ScooterMan101 » Dec 26, 2017 8:36 pm

Who can design a way to use the freewheel that is on the heavy square taper bb / square taper bb style cranksets, ... with the newer style direct mount cranksets ?
Direct Mount Cranksets are 3 piece, consisting of two crank arms , and a spindle .
See FSA, Sram, etc.

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by 12-C » Jan 01, 2018 12:17 am

ScooterMan101 wrote:
Dec 26, 2017 8:36 pm
Who can design a way to use the freewheel that is on the heavy square taper bb / square taper bb style cranksets, ... with the newer style direct mount cranksets ?
Direct Mount Cranksets are 3 piece, consisting of two crank arms , and a spindle .
See FSA, Sram, etc.
Shoot some pics and diagrams/ideas my way, I have some CAD skills. As long as I have exact measurements and diagrams I can draw up designs.

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by ScooterMan101 » Jan 06, 2018 10:28 pm

12-C

I have a picture of a Tiagra Road Shimano Hollowtec II 3 chainring crankset,
and
A Deore Mountain Shimano Hollowtec II 3 chainring crankset.

The Idea I have is to do this on a 3 x crankset, that way the inner chainring can be removed and the freewheel put in its place / in the space between the large chainring and the small chainring.

I am not sure how wide the current freewheels are .

The Space available on the Mountain Crankset is 10 mm to work with, or 12 mm if a new outter chainring is made which is flat.

The Space Available on the Road Crankset is 11mm for space for a freewheel if keeping the stock outer chainring, but if a custom made chainring is made that is flat then apx. 12 mm for the entire width for the freewheel.

Anyone have a freewheel that can measure the width of it ?

The outer chainring on both cranksets are dished, I am guessing so as to help with changing from the middle and outer chainring.

I am sure that a new outer chainring would have to be made anyway so as to have larger amount of teeth , so that there is less reduction needed from the mid drive to the crankset . ( chain from motor to crankset on the outer chainring position )

Both have the outer chainring mounted to the crank arm, the Mountain and Road have different BCD's , I can get that latter to you if you need.

So to do this I am guessing that all three chainrings need to be removed, a special spider made to hold the outer chainring and the freewheel, and another spider made to hold the inner chainring to the freewheel.

If you did not know the Shimano Hollowtec II system is a 2 piece crankset, meaning that the drive side also is connected to the spindle , 24mm OD, that goes through the bike to the other side where the other crank arm bolts up to it.
Attachments
IMG_1838.JPG
MTB Crankset
IMG_1835.JPG
Tiagra Crankset
IMG_1837.JPG
Tiagra Crankset
IMG_1839.JPG
MTB Crankset
Last edited by ScooterMan101 on Jan 07, 2018 1:16 am, edited 3 times in total.

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DanGT86
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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by DanGT86 » Jan 06, 2018 11:58 pm

Is this what you are going for?
510BE367-2723-4BD0-85E0-B53FCC479122.jpeg
510BE367-2723-4BD0-85E0-B53FCC479122.jpeg (234.24 KiB) Viewed 249 times
If so it requires machining this area into threads for the freewheel.
4E9C06BA-4214-4E6D-8BDD-5E72C6524F67.jpeg
4E9C06BA-4214-4E6D-8BDD-5E72C6524F67.jpeg (105.18 KiB) Viewed 249 times
Its covered here.
https://endless-sphere.com/forums/viewt ... 5&start=25

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by ScooterMan101 » Jan 07, 2018 1:08 am

That looks good .... but
The picture looks like there are still 3 chainrings , and that the chain from the front mid-drive motor is going into the inner chainring . ( would it not be better to reverse that for 2 reasons ? )

Is it a item that can be bought ?

Is there a way to just use the bolt holes for the chainrings to make a freewheel that would not have to have the spindle machined ? , since most of us do not have a machine shop .

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by DanGT86 » Jan 07, 2018 9:50 am

ScooterMan101 wrote:
Jan 07, 2018 1:08 am
That looks good .... but
The picture looks like there are still 3 chainrings , and that the chain from the front mid-drive motor is going into the inner chainring . ( would it not be better to reverse that for 2 reasons ? )

Is it a item that can be bought ?

Is there a way to just use the bolt holes for the chainrings to make a freewheel that would not have to have the spindle machined ? , since most of us do not have a machine shop .
Not my setup. Here is the original forum.
https://www.pedelecforum.de/forum/index ... rieb.4194/

I too would rather have the motor driven sprocket on the outside because that is usually the biggest and typically these setups need the reduction of a large motor driven sprocket.

This is not something that can be bought. Threading that crank with the rest of the arm whipping around would be a bit scary in a lathe but not unmanageable. Still quite a bit of special setup on that job and wouldn't be cheap to have done. Also, I believe only the multi chainring cranks have enough meat there to machine into threads. I have some hollowtech 2 single ring cranks on my bike and it doesn't look like there is enough there for freewheel threads.

The problem with using the chainring threads to attach a freewheel is that these external bearing Bottom brackets have the outboard bearing housing taking up a lot of real estate. The standard internal bearing BBs like the cyclone kit ones can be used with a longer spindle and give you back the room that you would lose with an external type.

One good thing about Hollowtechs is that you can run an 83mm length spindle with a 73mm BB frame. This gives you 10mm of side adjustment you can work with but will slightly throw off your side to side body positioning.

One bad thing about the Hollowtechs is that they have a 24mm spindle and I've only seen 25mm Id bearings available. The stock hollowtech seems to have a plastic insert in the bearing that takes up the slop between spindle and bearing. Seems strange to me but I trusted them.

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by ScooterMan101 » Jan 07, 2018 12:58 pm

The External Bearings are 44 mm OD, and 11-14 mm wide . ( Non Drive side is 11 mm but the drive side bearing looks to be 2 mm wider )

Anyway the bearings fit inside of the crank / spyder / inner chainring.

So there is enough space there , on my Mountain Shimano Hollowtec II crankset the space between the inner area where the innerchainring bolts bolt the smallest chainring is at least 50 mm, more like 52 mm to the threads.

So there is really at least 6 mm of space there , ( 3mm on each side/ all around , between the outer material of the bearing and the BCD / inner chainring bolts ) enough for a freewheel to be made to fit over the Bearings , and still connect the inner chainring mounting bolts,
and even more doable if the freewheel is made to bolt up to the outer chainring mounting bolts

DanGT86 wrote:
Jan 07, 2018 9:50 am


The problem with using the chainring threads to attach a freewheel is that these external bearing Bottom brackets have the outboard bearing housing taking up a lot of real estate. The standard internal bearing BBs like the cyclone kit ones can be used with a longer spindle and give you back the room that you would lose with an external type.


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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by DanGT86 » Jan 07, 2018 2:29 pm

I took some measurements. It looks doable but at least on a 73mm it would require some fancy machining of the threaded FW adapter. It would need to look like a spider. On a 68mm BB frame this might be possible with a simple round adapter that attaches to the small chainring circle (64mm?)
Here is what I found on mine:
HT crank measurements.jpg
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I'm thinking its not really worth it because the current ISIS options on the market using trials cranks seem to be holding up just fine.

Another alternative would be BMX cranks and spindles. I really like how simple the 3 piece crank designs are and you can buy all the parts separately to get whatever spindle length you need.
fsa-bmx-34.jpg
fsa-bmx-34.jpg (54.03 KiB) Viewed 191 times

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by DanGT86 » Jan 07, 2018 4:27 pm

This might solve a bunch of problems. Description says it uses hollowtech style cups. It has Shimano style Freewheel splines on the crank and uses a shimano splined freewheel. This could actually be the product many people have been waiting for. I remember years ago there were people broaching WI freewheels to get them to fit on shimano spline cassettes. Freewheel is 17mm wide and the description says the splines are 21mm long.
large_bonzcrankset3 dan.jpg
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large_bonz108splined__size-800-0.jpg
large_bonz108splined__size-800-0.jpg (23.67 KiB) Viewed 181 times
here is the link to the seller where I lifted the pics:
https://www.tartybikes.co.uk/cranksets/ ... oiMjMxIjt9


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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by ScooterMan101 » Jan 09, 2018 12:12 am

The $ 399 price kills is for a contender, and that is not including the chainrings or a freewheel .

The whole Idea for making a bolt on freewheel for Direct Mount ( like the much more affordable Race Face Cinch Cranks)
or
The Shimano Hollowtec II cranksets , is to have a low cost conversion to freewheel crank.
With a lower cost freewheel than the White Industries one , even a custom made , bolt on version could be $ 100 or so.

I think a whole re-designed freewheel to bolt onto the common BCD's is the way to do it. Once designed it could be made in Taiwan or China.

12-C wrote:
Jan 09, 2018 12:01 am
What about http://boxcomponents.com/vector-m30-p-crankset_2

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by Chalo » Jan 09, 2018 1:49 am

DanGT86 wrote:
Jan 07, 2018 2:29 pm
Another alternative would be BMX cranks and spindles. I really like how simple the 3 piece crank designs are and you can buy all the parts separately to get whatever spindle length you need.
That's what I was thinking. Put a threaded freewheel adapter inboard of the drive side crank with a Woodruff key to hold it.

It doesn't address the problem of freewheels barfing their guts out when you overrun them with motor power while not pedaling, but at least it's a simple implementation.

Another alternative is use a normal crank, gear the motor drive to match a normal pedal cadence, and develop a doggone backbone.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by 12-C » Jan 09, 2018 6:41 am

Chalo wrote:
Jan 09, 2018 1:49 am


It doesn't address the problem of freewheels barfing their guts out when you overrun them with motor power while not pedaling, but at least it's a simple implementation.
I would echo these sentiments regarding the freewheel. The lateral loads kill em. Imo the limited space for it all would exacerbate the problem even more and still necessitate the need for the ultra HD freewheel from sbp... The direct drive chain rings only exist because 1x setups became a thing. This they only really need about 4mm for the chain ring and a few more for a non laterally loaded retainer ring.

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by DanGT86 » Jan 09, 2018 1:26 pm

Definitely need either a support bearing for the WI ENO freewheels or the dual bearing HD unit from SBP which is a bit wider I think.

I thought up another possible solution but it again requires machining a few parts. I think the spider adapter that bolts to the Flanged freewheel could have a bearing in it that hangs over the external BB bearing cup. The cup would need to be turned or remade to a size that a bearing could be installed on it. Basically use the bearing cup outside diameter as the support bearing location to eliminate the side load while freewheeling issue. This would be the best way to reclaim some of the real estate lost due to the external BB cups being 10+mm wide. Still hard to stuff in a hollowtech though.

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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by Chalo » Jan 09, 2018 1:37 pm

A technical approach to the width issue could be the way I made a rear hub for my own bike, so that I could install an axle that was too big to fit through a bearing that would fit inside a freewheel thread.

On the freewheel side, I installed a thin section needle roller bearing. On the left side, I pressed in a large conventional cartridge bearing. Because the axial retention of the hub axle was only in one direction at that point, I made a ring to capture the cartridge bearing on the outside of the hub. Mine was booked with a 6 hole pattern, but it could just as easily have been an ID snap ring.

Even though I used this layout to get a smaller OD right side bearing, in a bottom bracket it would work to move the right side bearing inside the shell and reduce the width of the assembly.

Image
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Re: Design a Freewheel Crankset for Direct Mount Crankests

Post by DanGT86 » Jan 09, 2018 5:34 pm

Thats good thinking to move the right side bearing into the shell using a super thin bearing like that. Unfortunately the shimano hollowtech spindle is actually machined on the ends where it rides on the bearings. The middle of the undercut has a slightly rough texture that's not concentric with the machined journals. Looks like its forged rough like a slight hourglass shape with extra material in the bearing area. They must just take a small cleanup pass with a lathe to get it to spec. It was very subtle but about .005-.010" smaller in the middle which is a mile when you are talking bearings.

I had to measure it because I am using an 83mm length spindle with a 73mm BB. I was worried it would miss that part when I noticed it was varying diameters. Thin wall bearing inboard might still be manageable with a sleeve pressed over the spindle and some epoxy to fill the slight void under the sleeve if the bearing needed to ride on that part. I can measure mine next time I take it apart to see if the bearing section is long enough. I just don't have a whole lot of motivation to remove it because I don't actually even need a freewheeling bottom bracket for my stuff. I'm just a machinist who finds it interesting.

This is what I was thinking for the FW support bearing installed on the outboard bearing cup. It would still need a wacky looking spider to attach the inside threaded portion of the freewheel to the cranks somehow.
no bearing small.png
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all small.png
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