One leg cycling alterations
-
- Posts: 1
- Joined: Thu Feb 22, 2018 10:08 am
One leg cycling alterations
Postby david.123 » Thu Feb 22, 2018 10:12 am
-
- Posts: 22
- Joined: Tue Sep 27, 2016 11:20 am
Re: One leg cycling alterations
Postby rooftop » Thu Feb 22, 2018 12:38 pm
-
- Posts: 631
- Joined: Mon Jan 29, 2018 1:42 pm
Re: One leg cycling alterations
Postby Jmuzz » Thu Feb 22, 2018 1:49 pm
- Alex Simmons/RST
- Expert
- Posts: 4997
- Joined: Fri May 02, 2008 3:51 pm
- Contact:
Re: One leg cycling alterations
Postby Alex Simmons/RST » Thu Feb 22, 2018 4:55 pm
- bychosis
- Posts: 7250
- Joined: Sat Jan 14, 2012 1:10 pm
- Location: Lake Macquarie
Re: One leg cycling alterations
Postby bychosis » Thu Feb 22, 2018 5:16 pm
- MattyK
- Posts: 3252
- Joined: Fri Oct 01, 2010 1:07 pm
- Location: Melbourne
Re: One leg cycling alterations
Postby MattyK » Fri Feb 23, 2018 10:10 am
If you have (or retrofitted) a square taper BB, then I can envisage replacing the right crank retainer bolt with some adaptor* that is headed with a female thread into which you could screw a pedal.
Something like:
PLUS
PLUS
I'm not sure it would be comfortable at that height though.
*M8 x 1mm Male to 9/16'-20 TPI Female. I doubt such a thing exists but any machine shop should be able to make one, if they have the right tap.
- ValleyForge
- Posts: 1831
- Joined: Tue Jan 27, 2009 5:37 pm
- Location: Brisbane
Re: One leg cycling alterations
Postby ValleyForge » Fri Feb 23, 2018 11:53 am
If you have (or retrofitted) a square taper BB, then I can envisage replacing the right crank retainer bolt with some adaptor* that is headed with a female thread into which you could screw a pedal.
[quote]
Great idea - but given it's the drive side - I think it's in the too hard basket.
- MattyK
- Posts: 3252
- Joined: Fri Oct 01, 2010 1:07 pm
- Location: Melbourne
Re: One leg cycling alterations
Postby MattyK » Fri Feb 23, 2018 11:57 am
I don't believe that would make it any harder.ValleyForge wrote:Great idea - but given it's the drive side - I think it's in the too hard basket.MattyK wrote:What bike? (specifically what crankset and bottom bracket?)
If you have (or retrofitted) a square taper BB, then I can envisage replacing the right crank retainer bolt with some adaptor* that is headed with a female thread into which you could screw a pedal.
Worst case you could cut the crank arm off but I reckon it would be far enough away to not be a problem.
- ValleyForge
- Posts: 1831
- Joined: Tue Jan 27, 2009 5:37 pm
- Location: Brisbane
Re: One leg cycling alterations
Postby ValleyForge » Fri Feb 23, 2018 12:11 pm
I reckon you would need to. Else you will have a fair extension on the female fitting to clear the crank arm.MattyK wrote:I don't believe that would make it any harder.ValleyForge wrote:Great idea - but given it's the drive side - I think it's in the too hard basket.MattyK wrote:What bike? (specifically what crankset and bottom bracket?)
If you have (or retrofitted) a square taper BB, then I can envisage replacing the right crank retainer bolt with some adaptor* that is headed with a female thread into which you could screw a pedal.
Worst case you could cut the crank arm off but I reckon it would be far enough away to not be a problem.
- find_bruce
- Moderator
- Posts: 10579
- Joined: Mon May 09, 2011 8:42 pm
- Location: Sydney
Re: One leg cycling alterations
Postby find_bruce » Fri Feb 23, 2018 1:11 pm
The head on an m8 crank bolt is 14mm ~9/16. The nut for a 9/16 bolt is usually 13/16, ~21mm, which may not fit inside the crank. Plus a 175% step in the wrong direction means you need to be careful to leave enough meat in the middle to transition from one to the other.MattyK wrote:*M8 x 1mm Male to 9/16'-20 TPI Female. I doubt such a thing exists but any machine shop should be able to make one, if they have the right tap.
As you say it also may not be comfortable to have a pedal at the level of the bottom bracket.
If David can cope with a small revolution, I would look at drilling a new pedal thread to give a very short crank as Alex suggested.
If that doesn't work for David I would cut the crank off to avoid getting whacked by it and look at mounting a footpeg at a suitable position from the downtube.
- MattyK
- Posts: 3252
- Joined: Fri Oct 01, 2010 1:07 pm
- Location: Melbourne
Re: One leg cycling alterations
Postby MattyK » Fri Feb 23, 2018 1:32 pm
Look at my first pic above. That bolt looks much bigger than 14mm under the head.find_bruce wrote:The head on an m8 crank bolt is 14mm ~9/16. The nut for a 9/16 bolt is usually 13/16, ~21mm, which may not fit inside the crank. Plus a 175% step in the wrong direction means you need to be careful to leave enough meat in the middle to transition from one to the other.MattyK wrote:*M8 x 1mm Male to 9/16'-20 TPI Female. I doubt such a thing exists but any machine shop should be able to make one, if they have the right tap.
Of course it would have to be custom made anyway, so the details like that would be figured out at the design stage.
- Duck!
- Expert
- Posts: 9858
- Joined: Tue May 21, 2013 8:21 pm
- Location: On The Tools
Re: One leg cycling alterations
Postby Duck! » Fri Feb 23, 2018 11:59 pm
There's the old saying, "use it or lose it", and that's valid to several extents, and that applies to joint mobility as much as anything else. While high-level joint mobility may cause problems, limiting use of the joint can be just as harmful for joint health in the long term. Therefore I'd suggest using a short crank, around 150mm, which will still allow both legs to do a more equal portion of the work, and maintain mobility in the troublesome knee, but reduce the stress imposed by a larger range of movement. It would in all probability be better for the knee than removing almost all movement.
- Alex Simmons/RST
- Expert
- Posts: 4997
- Joined: Fri May 02, 2008 3:51 pm
- Contact:
Re: One leg cycling alterations
Postby Alex Simmons/RST » Sat Feb 24, 2018 11:18 am
While we don't know the extent of the issues the OP faces, for reference when I started back after amputation and had limited knee flexion on my prothesis leg side, I started with a 100mm crank a mate made for me (I was already using square taper cranks so finding and hacking down a crank arm wasn't that hard). That meant I could at least ride.Duck! wrote:Although not falling under the "quick and easy" criteria, I would suggest getting to the root of the knee problem and addressing that rather than trying to skirt around the issue with solutions that, even with the assistance of a motor unit, concentrate all stresses on the other leg, potentially blowing that up too.
There's the old saying, "use it or lose it", and that's valid to several extents, and that applies to joint mobility as much as anything else. While high-level joint mobility may cause problems, limiting use of the joint can be just as harmful for joint health in the long term. Therefore I'd suggest using a short crank, around 150mm, which will still allow both legs to do a more equal portion of the work, and maintain mobility in the troublesome knee, but reduce the stress imposed by a larger range of movement. It would in all probability be better for the knee than removing almost all movement.
Eventually as I improved I migrated to a 150mm crank arm and eventually regular 170mm crank arm. I also had a set of adjustable length SRM cranks on my indoor trainer bike which I could get down to 145mm and adjust as I went.
I had a big advantage of it being left side though. Much harder on the drive side.
- General Australian Cycling Topics
- Info / announcements
- Buying a bike / parts
- General Cycling Discussion
- The Bike Shed
- Cycling Health
- Cycling Safety and Advocacy
- Women's Cycling
- Bike & Gear Reviews
- Cycling Trade
- Stolen Bikes
- Bicycle FAQs
- Serious Biking
- Audax / Randonneuring
- Retro biking
- Commuting
- MTB
- Recumbents
- Fixed Gear/ Single Speed
- Track
- Electric Bicycles
- Cyclocross and Gravel Grinding
- Dragsters / Lowriders / Cruisers
- Children's Bikes
- Cargo Bikes and Utility Cycling
- Road Racing
- Road Biking
- Training
- Time Trial
- Triathlon
- International and National Tours and Events
- Cycle Touring
- Touring Australia
- Touring Overseas
- Touring Bikes and Equipment
- Australia
- Western Australia
- New South Wales
- Queensland
- South Australia
- Victoria
- ACT
- Tasmania
- Northern Territory
- Country & Regional
- The Market Place
- Member to Member Bike and Gear Sales
- Want to Buy, Group Buy, Swap
- My Bikes or Gear Elsewhere
- Cycling Brands
- Cannondale
- Garmin
- Giant
- Shimano
- Trek
Who is online
Users browsing this forum: familyguy
- All times are UTC+11:00
- Top
- Delete cookies
About the Australian Cycling Forums
The Australian Cycling Forums is a welcoming community where you can ask questions and talk about the type of bikes and cycling topics you like.
Bicycles Network Australia
Forum Information
Connect with BNA
This website uses affiliate links to retail platforms including ebay, amazon, proviz and ribble.