Why the Cruzbike is faster on hills

Jim Lipscomb, one of my Cruzbike customers/riders recently wrote Maria Parker (Cruzbike) and me an explanation of why he believes the Cruzbike is faster on hills.  For those of you who do a lot of research into recumbent bikes, I thought you might be interested in reading his analysis.

 

Dear Maria,

You mentioned that: “… I’d like to hear your explanation for why it (Cruzbike) is faster on hills.”

My take:
Cruzbikes appear to be at least 1 mph faster than other recumbent bikes overall.  In detail, faster both on hills and on the flats too (100-mile record on V20:http://cruzbike.com/blog/2015/10/13/record-report-oslund-sets-100-mile-record-on-v20/ ).

Firstly, this is real.
* I timed rides overall under various conditions of my Cruzbike Silvio vs. my Volae team, both bikes half-way racing recumbents.  The Silvio shows a 1, 2, and 3 mph advantage depending on test conditions.  My tests were pretty skimpy and comparing apples to oranges, so the fewer details the better.  I’ll officially go with 1 mph to the Silvio.
*  Ben Tomblin reports 1 mph faster overall over Bacchetta CA/2 in his report on the Solo Hoodoo 500
http://03bbf98.netsolhost.com/blog/2015/09/30/race-report-ben-tomblins-solo-hoodoo-500/

The magic is not so much what is in the Cruzbke, but the anti-magic on standard recumbents.

(1) The main reason for Cruzbike speed seems to be that power goes from the pedals to the ground.  Dirty little secret of the recumbent business: Traditional recumbents have long chains with losses in
* idlers (each link in the chain must climb a tiny hill to pass over an idler),
* chain stretch with each power pulse (3 times longer straight stretch of chain under tension),
* frame bend (the long distance between hubs gives purchase to substantially bend the traditional recumbent frame).
totaling to as if lightly dragging the brakes.  If you ever had brakes just very lightly dragging, so lightly that you have to spin the wheel and listen to hear the rubbing, you know that even that little bit can lose 1 mph.  It does not take much.  Sorry, nobody has numbers; it’s a crime.

(2) Another reason, secondary in my experience, that Cruzbikes are faster is that riders can rock the frame to push it against the pedals.  I say this is less of a factor, because all of my speed numbers above (1, 2, and 3 mph in different test conditions) I got without any frame rocking.  Frame rocking is highlighted in http://cruzbike.com/records   My experience is that I think I can get an additional 1 mph up a hill with frame rocking, just an estimate, looking at the speedometer.  This is just on hills, and just for as long as I’ve got the arms for it.

(3) Weight seems to have comparatively little to do with speed.  Cruzbikes are heavy compared to other racing recumbents, which can be a big source of skepticism:
* 26 lbs Cruzbike V20
* 21 lbs Bacchetta Carbon Aero
* 15-16 lbs Carbent Sea Dragon or Raven Pro with lightweight components
However, the Bicycle Speed Power Calculator at
http://www.kreuzotter.de/english/espeed.htm
shows that for my weigh and speed at least:
30 lbs = 1 mph difference climbing a hill,
pretty much independent of speed.  Adding 30 lbs slows the climb from 6 mph to 5 or from 15 mph to 14 mph.  So the 5-10 lb heavier V20 loses only 1/6 to 1/3 mph on account of weight.  Not significant compared to Cruzbike gains listed above in the 1+ mph range.

SUGGESTION
I suggest updating your webpage
http://cruzbike.com/records
combining points 1-3 above.
Just focusing on frame rocking is focusing on a minor aspect of speed and does not address weight skepticism.

WHY
So, why am I writing now?  If you have been following the Tarzan Ride, Kurt Searvogel’s High Annual Mileage Record (HAM’R) ride, you may have heard that he rode a Bacchetta part of the time.

https://www.facebook.com/tarzanrides/

And just today as he finished he wrote:
“It appears that we finished this endeavor …. Today we are … before heading to Vite Bikes tomorrow to pick up a bent for Alicia. If she is going to go after the women’s record she will need the right tools and training. ….”

Oh noooooo.  I wrote in reply my short version, as you can see on that facebook page:
James Lipscomb   ‘Sigh, “… heading to Vite Bikes tomorrow to pick up a bent … right tools ….” No Cruzbikes that I saw on the Vite Bike page. Riding part-time a non-Cruzbike recumbent probably cost Kurt 1,000 miles. Dirty little secret of the recumbent business: Cruzbikes seem to be at least 1 mph faster than other racing recumbents, whose long chains have losses in idlers, chain stretch, and frame bend, as if lightly dragging the brakes (weight has comparatively little to do with speed). Nobody knows, except the few Cruzbike riders. For me the ride difference is ohgodohgodohgod.’

Regards,
Jim Lipscomb

 

 

Eat, sleep, ride, Jim,

Robert