It's amazing what a difference 6 inches makes!

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It's amazing what a difference 6 inches makes!

Postby Cyclaholic » Fri Jun 27, 2008 9:45 am

I went up to my local the other day to get my new headset fitted. They were short handed so the owner said that if I wanted to I could use the workshop and do it myself. While I was in the workshop I spotted a decent looking, second hand 26" steel fork and said to myself "self, what do you reckon she'd be like with a 26 instead of a 20 up front?"

After bringing my awesome negotiating skills to bear on my LBS proprietor ("how much?"... "shout me lunch today and its yours".... "OK then, pizza?"... "yeh OK") and it was mine. So when I got home it only took 20 minutes to swap over the front end from 20" to 26".

The first thing I noticed is that the front end went up (really?... naaaaah! :roll: ) but it didn't really look that much higher until I sat, actually laid down, on her and found that the handlebar is right in my line of sight, and I felt like I was lying down not just reclining back. It's workable but will take a little time to get used to, I think. The head angle has decreased a little (more laid back) so the front wheel flops more easily into the turn, especially at very low speed.

I went up to the shops for her 26/26 maiden voyage, mainly because I get to go up the T-way, which is nice and smooth and has no traffic but for one bus every 10 minutes. It was immediately obvious that there was tonnes more feedback from the front wheel! I could tell exactly what the steering was doing, by comparison the 20" was more of an educated guess. The bike path from my place to the T-way is a bit rough but the bigger front wheel made it significantly smoother...... Then I hit the smooth T-way and opened up the throttle, and that's when the fun really began!

She immediately accelerated up to 36km/hr and I could cruise at that speed with the same effort that used to get me around 28 - 30. The handling at speed is definitely less twitchy, and is easier to hold a line around fast sweeping curves. That was on a nice flat and slightly undulating stretch.... then I went up the shallow-ish climb leading up to the shops which was just as slow as ever :oops: . After drawing the usual crowd at the rack I went and got my girl a Nintendo DS (because she's done extremely well in school this semester) and coasted back down that climb. Previously I was hitting around 42 - 43km/hr but this time I hit 56km/hr and soiled my shorts.

And finally, the deal clincher! last night's ride home was head on into a very stiff west-sou-wester as a cold front swept through, and I was comfortably cruising past everyone on uprights like they were standing still (ok, some of them actually were standing still) but seriously, what a huge difference! with the 20" I could feel the wind on my legs, chest, and face, but with the 26" I feel the wind predominantly on my legs but the rest of my body is in my leg's wind shadow and I think that made a huge difference.

So, what started as an experiment to satisfy my curiosity has completely transformed this bike. I'm amazed what a huge difference it made, and it's really got me thinking about other improvements that could make a significant difference..... tail fairing maybe?
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by BNA » Fri Jun 27, 2008 11:29 am

BNA
 

Postby Kalgrm » Fri Jun 27, 2008 11:29 am

Good right up Cyclaholic. looks like you're on a winner there.

Larger wheel diameters are the biggest factor in reducing rolling resistance*. You've also managed to reduce your frontal area, so your aerodynamics have improved in one giant leap. Good work!

There was a threadin the last few days on the Bachetta forum about the Aerotrunk. The guy had done a series of roll-down tests in calm conditions (wife shuttling him back to the top of the hill between runs). They showed his maximum speed - presumably terminal velocity -only increased 0.5 mph from 34.5 to 35. He has decided to take it off, since it's weight he has to carry up the hills with no discernible benefit.

Cheers,
Graeme

(* I found the same thing when I switch from 26" wheels to 700c wheels on my Giro 26)
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Postby Cyclaholic » Fri Jun 27, 2008 11:46 am

G'day Graeme,

My engineering brain thanks you for that link. 8) ...interesting results there, and a good read.

I think in addition to the increase in diameter, the other contributing factor was that the 20" had a big, fat, heavy, cheap, low pressure Kenda, and the 26" has a skinny Sport Contact at double the pressure of the Kenda.

I was toying with the idea of a 700c on the rear because I have a Ksyrium Elite that is way more aero than the current 26" rear wheel, but I'm pretty much at my limit for seat height... I almost took a spill yesterday while waiting at an intersection because of the crosswind while balancing on tippytoes :oops:

By the way, is it me or does gusty crosswind have a much bigger effect on holding a straight line on the 'bent compared to the upright?
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Postby Kalgrm » Fri Jun 27, 2008 12:34 pm

Cyclaholic wrote:By the way, is it me or does gusty crosswind have a much bigger effect on holding a straight line on the 'bent compared to the upright?

That's just you getting used to the way the bike handles.

I now run a ghetto rear disc wheel (spoke cover). When I first put it on, I was very conscious of the effect of any cross wind. However, within a few days, I didn't notice the effect any more, to the point where I'm now wondering if the wind on those early rides was MUCH stronger than I thought! ;)

You'll get used to it soon.

Cheers,
Graeme
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Postby froodh » Fri Jun 27, 2008 6:45 pm

Hi Cyclaholic,

Wish you posted this before! I put an order in only this morning for a Toscana 2026 USS from Just Bents. Maybe I should have went for the 2626 they have instead.

Oh well, comfort, not speed, is my main concern and the USS is better for this (I hope), and I don't think the Toscana 2626 comes in USS.

cheers,
Jeremy
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Postby Cyclaholic » Fri Jun 27, 2008 9:53 pm

froodh wrote:Hi Cyclaholic,

Wish you posted this before! I put an order in only this morning for a Toscana 2026 USS from Just Bents. Maybe I should have went for the 2626 they have instead.

Oh well, comfort, not speed, is my main concern and the USS is better for this (I hope), and I don't think the Toscana 2626 comes in USS.

cheers,
Jeremy


Hey! so you pulled the trigger on the Toscana, congrats mate!
Don't worry, you'll enjoy the bike... and don't worry, doing the 26" front wheel conversion is a piece of cake if you ever feel so inclined..... you may have the honor of the only 26/26 USS Toscana in existence!
:lol:
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Postby Cyclaholic » Fri Jun 27, 2008 9:59 pm

Kalgrm wrote:
Cyclaholic wrote:By the way, is it me or does gusty crosswind have a much bigger effect on holding a straight line on the 'bent compared to the upright?

That's just you getting used to the way the bike handles.

Thanks mate, that's good to know.

Kalgrm wrote:I now run a ghetto rear disc wheel (spoke cover). When I first put it on, I was very conscious of the effect of any cross wind. However, within a few days, I didn't notice the effect any more, to the point where I'm now wondering if the wind on those early rides was MUCH stronger than I thought! ;)

You'll get used to it soon.

Cheers,
Graeme

Tell me more! is your wheel cover home made? does it make a noticeable difference? i.e. enough to justify the weight penalty?

Just thinking it through, the rear wheel runs in disturbed air so would you have a net greater aero benefit in using a cover on the front wheel? or does that induce handling/steering issues I'm not aware of? How about covers on both front and rear wheels?

Sorry to bombard you with so many questions, I'm just a wide-eyed newbie. :oops:
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Postby Kalgrm » Sun Jun 29, 2008 7:35 pm

Cyclaholic wrote:Tell me more! is your wheel cover home made? does it make a noticeable difference? i.e. enough to justify the weight penalty?

Just thinking it through, the rear wheel runs in disturbed air so would you have a net greater aero benefit in using a cover on the front wheel? or does that induce handling/steering issues I'm not aware of? How about covers on both front and rear wheels?

It makes a small but noticeable difference to my speed, especially in headwinds and downhill runs. I'm happy enough with it to keep it.

Putting a spoke cover on the front wheel is dangerous on the open road because cross winds will throw your steering out. Don't do it. :wink: On the rear wheel, especially at speed, the cover acts to stabilise your path in a similar way to flights on a dart. Gusty cross winds were tricky to start with, but not now.

One day I'll put together a "How to" thread to show how I made my spoke covers. One day ....

Cheers,
Graeme
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Postby Storm » Sun Jun 29, 2008 9:32 pm

Can you show us a picture of your homemade wheeldisc, is it cloth or plastic?
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Postby AusAce » Mon Jul 07, 2008 2:57 am

I imagine the speed increase is more due to your torso being much more laid back. Up 6 in front is like lowering your seat back 6". a 20/20 geared right would be similar in speed to a 26/26 a little more rolling resistance but both much less air resistance then 20/26
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Postby Cyclaholic » Mon Jul 07, 2008 9:59 am

AusAce wrote:I imagine the speed increase is more due to your torso being much more laid back. Up 6 in front is like lowering your seat back 6". a 20/20 geared right would be similar in speed to a 26/26 a little more rolling resistance but both much less air resistance then 20/26


Yes, the torso is more reclined, plus the bottom bracket went up a fair bit so my torso is in my leg's wind shadow to a greater extent.

I'm using a mountain bike helmet with a peak, I wonder how much difference a teardrop shaped helmet would make?....like the ones you see in time trials. I've never even seen one of those in the shops, where do you buy them?
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The other way.................

Postby Freddyflatfoot » Mon Jul 07, 2008 3:46 pm

I was realising that I was very uncomfortable on stops with the extra height the suspension fork added to my SWB (3" for the BB, and 1 1/2" extra seat height), so I have decided to go the other way, and lower my front end, by swapping the suspension fork for a rigid one.
Result?
The bike feels a lot smaller/shorter, and a whole lot more comfortable!
I think this setup will be far better in stop/start traffic situations.
I have yet to take her out on a decent ride, but the setup is the same as I started out with, so should be happy with it. She was actually faster and more stable at speed, than I could manage with the front suspension. I actually think I could climb better, as the seat is a bit more upright, and should be able to brace myself a bit better for climbing.
Cheers!
Rob
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