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alevand
human power expert

USA
3706 Posts

Posted - 02/11/2020 :  07:10:00  Show Profile  Visit alevand's Homepage  Reply with Quote
Well, I was planning to attend the World HPV championships on July 12th weekend, but I looked today and its now changed to the weekend of the 18th, which collides with my wife's family reunion in Ireland on that Saturday. I still want to tour around Ireland and UK, the Netherlands would have been great, so I need a bike that fits into a bike box, thus the Carp Apart is born.

C:
Tony Levand

alevand
human power expert

USA
3706 Posts

Posted - 02/11/2020 :  07:25:34  Show Profile  Visit alevand's Homepage  Reply with Quote
Taking a preliminary view, a lwb or swb, both can break down to the same size. Im thinking a 451 front wheel and 700c rear. I want at least 45 degrees steering on a lwb, 25 degrees on a swb.

swb is lighter
lwb more stable
swb is shorter
lwb rides better
swb handles corners better
lwb better on straight open road
swb has more storage in back
lwb is simpler
swb has direct steering
lwb has more traction in gravel or mud
swb has no chain under the seat
lwb much better off road
swb needs narrow hub
lwb needs narrow BB
swb I have a 700c front rear wheel.
lwb I have a 451 front wheel and 700c rear.
lwb I have the narrow BB
lwb, front suspension possible with vps.
swb, vps interferes with feet down.
Both need the sun tour s5 derailleur, swb for leg clearance, lwb for smaller fairing bulge.
swb will be under geared or needs big sprockets. I have a 60 on 110 bc.


C:
Tony Levand

Edited by - alevand on 02/11/2020 07:38:37
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alevand
human power expert

USA
3706 Posts

Posted - 02/13/2020 :  02:21:43  Show Profile  Visit alevand's Homepage  Reply with Quote
Ive narrowed it down to one of these concepts:



C:
Tony Levand
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Balor
recumbent guru

Russia
946 Posts

Posted - 02/13/2020 :  06:22:07  Show Profile  Reply with Quote
All your 'carps' utilize a 'lean forward' rider position?
To be frank, it looks very uncomfortable, and certainly IS for me...
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warren
human power expert

USA
6528 Posts

Posted - 02/13/2020 :  10:11:09  Show Profile  Visit warren's Homepage  Reply with Quote
Your latest 'liner riding position looks a lot like that of the the Mango speedbike. It allows for a tiny package.
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alevand
human power expert

USA
3706 Posts

Posted - 02/13/2020 :  10:38:01  Show Profile  Visit alevand's Homepage  Reply with Quote
Im a little torn on the linear drive, no one ever has been successful with it, but it lowers my feet by 12 inches and allows the leaned forward position. The rwd version needs a fairing 2 inches wider, but may not be an issue if connecting rods are under the arms, the rwd chain drive is much simpler.

C:
Tony Levand
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warren
human power expert

USA
6528 Posts

Posted - 02/13/2020 :  13:16:13  Show Profile  Visit warren's Homepage  Reply with Quote
I saw that and was going to comment about it. IMO it would be better to use 100mm or even shorter cranks than linear drive.
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Balor
recumbent guru

Russia
946 Posts

Posted - 02/13/2020 :  15:26:33  Show Profile  Reply with Quote
quote:
Originally posted by warren

I saw that and was going to comment about it. IMO it would be better to use 100mm or even shorter cranks than linear drive.



If this article is of any indication (Hephasteus has PhD in biomechanics presumably):
http://lefthandedcyclist.blogspot.com/2014/03/why-hill-climbing-is-hard-or-efficiency.html

Than linear drives excel in slow speed climbing and not much else - pretty much reverse what you want for a fast, fully faired HPV. Small wonder even K-drive was discarded eventually.
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alevand
human power expert

USA
3706 Posts

Posted - 02/13/2020 :  15:27:30  Show Profile  Visit alevand's Homepage  Reply with Quote
I ordered tubing from Wicks today. I have it narrowed down to 3 concepts, upper left, lower right and center. I am going to try the linear drive, and if it doesn't work out, I'll cut it up and make a lwb carp.

Hephaestus makes no mention of a linear drive. I am making a slider-crank mechanism.

C:
Tony Levand

Edited by - alevand on 02/13/2020 15:48:45
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Balor
recumbent guru

Russia
946 Posts

Posted - 02/13/2020 :  23:17:12  Show Profile  Reply with Quote
quote:
Originally posted by alevand

I ordered tubing from Wicks today. I have it narrowed down to 3 concepts, upper left, lower right and center. I am going to try the linear drive, and if it doesn't work out, I'll cut it up and make a lwb carp.

Hephaestus makes no mention of a linear drive. I am making a slider-crank mechanism.

C:
Tony Levand



From the end of the article:

Lastly we come to that old favorite, the constant-torque treadle.
We know from the historical record that these systems can not be pedaled very quickly and consequently cannot produce high power levels. However, they do produce a constant torque throughout the stroke and this has to be more efficient than applying a large force through the forwardstroke, backstroke and upstroke of the pedal cycle. And there is some historical evidence that such systems excelled at hill climbing.


Admittedly, 'linear drive' is about as vague of a term as a 'recumbent' - some of them may indeed be as more efficient biomechanically than simple cranks, whether it will be worth extra weight, complexisty and friction is an other question...

Edited by - Balor on 02/13/2020 23:17:40
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alevand
human power expert

USA
3706 Posts

Posted - 02/14/2020 :  10:54:01  Show Profile  Visit alevand's Homepage  Reply with Quote
I am going to make a linear drive slider crank mule to test.

C:
Tony Levand

Edited by - alevand on 02/14/2020 10:58:31
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Balor
recumbent guru

Russia
946 Posts

Posted - 02/14/2020 :  12:30:16  Show Profile  Reply with Quote
quote:
Originally posted by alevand

I am going to make a linear drive slider crank mule to test.

C:
Tony Levand



Great idea! Do test relative performance on flats and uphill, I'm very interested personally.
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SpiderMonkey
recumbent guru

USA
690 Posts

Posted - 02/18/2020 :  08:27:41  Show Profile  Reply with Quote
I wonder how much training can help with linear drive. Yesterday was changing-the-oil day in the Rohloff hubs, and so the wife and I took a ride. Prescribed procedure calls for some backward pedaling to help mix in the cleaning oil.

It is really hard to pedal backwards.
It's not just the lack of resistance (as pedaling forward w/o resistance shows). It's a complete lack of muscle memory for backward pedaling. I wonder how long it would take to get good at it, or linear drive.

--SpiderMonkey
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Balor
recumbent guru

Russia
946 Posts

Posted - 02/18/2020 :  11:57:58  Show Profile  Reply with Quote
quote:
Originally posted by SpiderMonkey

I wonder how much training can help with linear drive. Yesterday was changing-the-oil day in the Rohloff hubs, and so the wife and I took a ride. Prescribed procedure calls for some backward pedaling to help mix in the cleaning oil.

It is really hard to pedal backwards.
It's not just the lack of resistance (as pedaling forward w/o resistance shows). It's a complete lack of muscle memory for backward pedaling. I wonder how long it would take to get good at it, or linear drive.

--SpiderMonkey



Yea, pedalling though dead spots is EXTREMELLY choppy. Yet, on a trainer and using upright LWB position with BB a bit below seat, I've managed MORE watts than in conventional pedalling!
https://www.strava.com/activities/2010532150/analysis

(Real watts as crosschecked by two power meters is 10% below that value)

Replicating it 'in the field' was harder though - it somehow upsets your steering even.

Edited by - Balor on 02/18/2020 12:00:16
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alevand
human power expert

USA
3706 Posts

Posted - 03/03/2020 :  16:38:20  Show Profile  Visit alevand's Homepage  Reply with Quote
Im thinking simple lwb dual 700 with tail box and higher seat (10 in). Lots of hills and rough roads.


C:
Tony Levand

Edited by - alevand on 03/05/2020 12:17:31
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