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Crank radius reduction

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SK6

Turbo Monkey
Jul 10, 2001
7,596
0
Shut up and ride...
I was at the gym yesterday and had a conversation with the director. He had shown me an aluminum piece that goes on the crank that shortens the location of the pedal (platform). It was machined aluminum that had 4 holes to vary the actual pedal distance.

Its use is for reducing the actual spin radius. However, this particular one is a bit precarious, and the director was looking for an inexpensive alternative to this particular device.

Any ideas would be greatly appreciated. This is for an older lady who would like to cycle, but can’t due to her physical limitations.

I have this posted in the DH and lounge as well.

Regards,

SK6
 

SK6

Turbo Monkey
Jul 10, 2001
7,596
0
Shut up and ride...
Wumpus said:
If you are talking about these, they don't change the radius.

:think: They actually do since the distance of the radius is reduced from the centerline of the radius to the circumference (outer edge of the circle) Since the reduction from the centerline is decreased, in this case by the height of the block, it in fact makes the pedal diameter shorter. I refer to pedal as the actual spin v the physical pedal.

The actual application is for stationary bikes, some of the members have a difficult time with the actual spin radius. The most inexpensive solution is the use of BMX cranks that someone had mentioned.

Thoughts?
 

thaflyinfatman

Turbo Monkey
Jul 20, 2002
1,578
0
Victoria
Bicyclist said:
No, the radius is the same, the circle is just translated however tall those blocks are.

^^What he said. It appears to shorten the radius when the crank is at the 6 o'clock position, but it also lengthens it by the same amount at the 12 o'clock position. The actual result is simply a net translation of the effective centre of the circle upwards.
 

SK6

Turbo Monkey
Jul 10, 2001
7,596
0
Shut up and ride...
thaflyinfatman said:
^^What he said. It appears to shorten the radius when the crank is at the 6 o'clock position, but it also lengthens it by the same amount at the 12 o'clock position. The actual result is simply a net translation of the effective centre of the circle upwards.
ahhhh......ok. :thumb:

changing name to...."need more coffee" :imstupid: :D
 

Tootrikky

Monkey
Jul 31, 2003
772
0
Mount Vernon
thaflyinfatman said:
^^What he said. It appears to shorten the radius when the crank is at the 6 o'clock position, but it also lengthens it by the same amount at the 12 o'clock position. The actual result is simply a net translation of the effective centre of the circle upwards.

My bad obviously didn't think about that. So much for the cheap route! Good catch though.