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Runxner
recumbent enthusiast

Australia
333 Posts

Posted - 03/03/2010 :  12:28:48  Show Profile  Reply with Quote
Is anyone thinking what I'm thinking?

With a MBB and a crank you can minimise the pedal steer with the right angles but with a linear drive the force would always be at the exact same angle and combined could have nil pedal steer. ? Or has that one been done too?

Team Low-Life
Lowracer Test Pilot/Evangelist
Adelaide, Australia
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Dana Barlow
recumbent enthusiast

322 Posts

Posted - 03/03/2010 :  12:38:37  Show Profile  Visit Dana Barlow's Homepage  Reply with Quote
"Are you saying that moving BB are no good?
or could you not ride one?"
?? You sure missed all the points,and any record ever set on a BB mounted to a fork design would of been faster if it had been BB as part of main frame.
Dose not make it any less fun to ride,just less effient for your power.
I think BB on fork was fun and I had good time riding one around.

Dana
Team Strange
"Strange One","Too Strange","Strange Try"
Miami Fla.
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DocBB
Starting Member

France
18 Posts

Posted - 03/04/2010 :  01:40:48  Show Profile  Reply with Quote
quote:
Originally posted by nigel schroder

Do you have any more pictures or drawing of "speculoos recumbents" I prefer the one's with out the over shoulder frame.

Cheers Nigel



heres is another "open" design originally in 2 X 559 very pleasant to race
the head set is a "flevo" like or python



one thing not easy to find is the good "push angle"


it seem that the open angle beteen pivot axis and a line between the seat and BB shoul be around 60°(according Laurent Dechene) /65°(according Tom Traylor) if you're looking to most of the "good" designs the angle range is 58° to 68° . the more it closes the less pedal-steering you got
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Dana Barlow
recumbent enthusiast

322 Posts

Posted - 03/04/2010 :  06:37:06  Show Profile  Visit Dana Barlow's Homepage  Reply with Quote
IN photo ,What makes that feel fairly good is that your hands form a strait "T" with head tube letting hands hold off pedal twist ,as long as the bar is wide enough to give a far lever . The wider the handel bars the less wast in power holding back pedal steer .


Dana
Team Strange
"Strange One","Too Strange","Strange Try"
Miami Fla.

Edited by - Dana Barlow on 03/04/2010 22:00:02
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DocBB
Starting Member

France
18 Posts

Posted - 03/05/2010 :  20:13:44  Show Profile  Reply with Quote
here is another sample of an open MBB


the problem of this peculiar bike was a lack of adherence in rising high degree slopes due to a relative short wheel base (108 cm) and high CG ( 80 cm) but it was great in standard runs and long distance races

But it could easily be enhanced with shorter wheels and as prone on the picture fixing the seat a little more ahead

note: again a "flevo-like" head set

Edited by - DocBB on 03/05/2010 20:18:32
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nigel schroder
recumbent enthusiast

New Zealand
190 Posts

Posted - 03/10/2010 :  20:11:56  Show Profile  Reply with Quote
What size tubing should I use?

I can only get mild steel ,2mm wall thickness.
I used 2" last time, could I go smaller?

I weigh 100kg
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DocBB
Starting Member

France
18 Posts

Posted - 03/11/2010 :  02:07:28  Show Profile  Reply with Quote
It is not my bike, but the tubes came from old shopped bikes or A37 steel 16 mm / 1 mm
ou 28 mm / 1 mm

or this one also


see the headset


completely cleaned

Edited by - DocBB on 03/11/2010 05:36:46
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25hz
human power supergeek

Canada
1223 Posts

Posted - 03/11/2010 :  07:47:58  Show Profile  Visit 25hz's Homepage  Reply with Quote
http://tinyurl.com/ykzlv6z

Edited by - 25hz on 03/11/2010 12:04:46
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DocBB
Starting Member

France
18 Posts

Posted - 03/11/2010 :  19:48:09  Show Profile  Reply with Quote
quote:
Originally posted by 25hz

http://tinyurl.com/ykzlv6z



you meant that ?

a state of the art if you read the french forum :

So: the Vademecum of amateur MBB designer

1) Measure your inseam : go pick a large-format comic, in a doorway up the good comics in keeping it perpendicular to the door jamb and draws a line, with your feet apart 20 cm measure, re-measure in order to have fairly reliable measurment

2) select the front wheel (available, program, Low-/Mid-/ High-racer)
3) choose an head set angle : 55 ° seems a good option also a 8 to 12 cm trail
4) select the seat height, the reference being the lowest point in the hollow (for a shovel kind Optima™ for a "chair" the middle of the flat plane,) 40 to 47 cm for a semi Lowracer in 559 or 620 seems correct; lower and you'll have probably to have a smaller front wheel.
5) try to bring the seat as near as possible from headset axis, estimate the need of space and the diameter of the tubes of the head set, if necessary, modify the seat height
6) from the bottom of the seat (already identified) trace an arc of maximum diameter of the inseam (step 1) or 2 to 3 cm smaller
7) position the crank shaft on this circle with the constraint that the radius of the circle makes an angle (open backwards) (thrust angle in french "angle pivot-poussée" on the drawning) maximum of 66 ° (65 ° according to pictures of Tom Traylor's bikes, 60 ° according to Laurent Dechene) with the axis of direction, knowing that the more the angle is closed (the more you lift the seat and / or lower the pedals) the less the pedalsteer.


8) this is done, check that your heels do not touch the ground (mini height of the bracket: crank length + length between the heel of shoe and pedal axle and you can give 2 cm margin) nor the derailleur when pedaling ( minimum base (wheel spindle / bottom bracket) 39 cm), otherwise lift the BB on his circle (step 6) ; the height of the BB on the bikes "which run" seems to be between 0 cm (seat height) and + 20cm with no particular problem (check the thrust angle)
9) drawing the front frame , two forks in V shape seem sufficient in case of metal frame as more rigid frames experienced failures due too much rigidity. Build light to reduce the "wheel flop". A 7 cm wide headset seems acceptable, for the "forks" it seems sensible for each one to measure spreads based on his (her) morphotype (valgus or varus) : measure the clearances taking in account of the feet spacing on the cranck; if necessary use pedal retractors (KneeSavers) Caution to the placement of the brakes, do not tempt the cutter devil that haunts bike enthusiasts!
10) decide the inclination of the seat from 25 ° (aérodynamique) to 45 ° (better in rising and mountains) and keep an eye on the thrust angle which can lead to shift the crank)
11) Draw the rear frame and rear fork depending on the selected rear wheel ; keep in mind that if the seat is high, you'll need a longer wheelbase : by 2.5 (mini observed) to 3.2 (as usual) times the height of the seat (maybe a little less if the pilot is lean) in order to keep weight on the front (around 55 to 60%) to avoid wheelslip in rise; anyway in a lowracer the pilot placement will increase the wheelbase.
12) choose whether or not a bar on the shoulder, where appropriate take account of space for the chest of the driver with some variation of seat position.
13) once the general geometry designed to choose either a U-shaped handlebars with a very forward stem, the drawback would be some repported brutal impigement of the shins during sliding pedals, or handlebar bound on or near the headset ; position it where the hands fall (46 cm wide) and think through its binding to the frame

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nigel schroder
recumbent enthusiast

New Zealand
190 Posts

Posted - 05/23/2010 :  11:57:44  Show Profile  Reply with Quote
Hi DocBB

On the the Lawrence Kouign Amann Dechene (Kaldi)what size are the chain rings you use?

ps: the bike looks even cooler now


"It never gets easier, you just go faster."- Greg LeMond

"Don't buy upgrades; ride up grades." - Eddy Merckx
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DocBB
Starting Member

France
18 Posts

Posted - 05/25/2010 :  19:18:20  Show Profile  Reply with Quote
quote:
Originally posted by nigel schroder

Hi DocBB

On the the Lawrence Kouign Amann Dechene (Kaldi)what size are the chain rings you use?

ps: the bike looks even cooler now

"It never gets easier, you just go faster."- Greg LeMond

"Don't buy upgrades; ride up grades." - Eddy Merckx



it is not my bike, but I asked Geoffroy

he uses 155 mm cranks and a rotor 50/63 and shimano 10 rings, 11-27 , but the 27 doesn' t work ,you have to climb a last at à 15km/h minimum, and for hill racing 56/44.
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nigel schroder
recumbent enthusiast

New Zealand
190 Posts

Posted - 05/25/2010 :  23:28:14  Show Profile  Reply with Quote



quote:
it is not my bike, but I asked Geoffroy

he uses 155 mm cranks and a rotor 50/63 and shimano 10 rings, 11-27 , but the 27 doesn' t work ,you have to climb a last at à 15km/h minimum, and for hill racing 56/44.


Its got a 451 on the front hasn't it?

I'm using 406 wheel.
150 mm cranks
50/65 chain rings
12-32 8 speed

Do you think I will need to go bigger?

cheers Nigel

ps: I will post pic when I get more of it built.


"It never gets easier, you just go faster."- Greg LeMond

"Don't buy upgrades; ride up grades." - Eddy Merckx
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nigel schroder
recumbent enthusiast

New Zealand
190 Posts

Posted - 06/15/2010 :  01:15:38  Show Profile  Reply with Quote
I've got the frame built , this is what it looks like so far.

Just need to add a seat and handlebars.

What do you think?





"It never gets easier, you just go faster."- Greg LeMond

"Don't buy upgrades; ride up grades." - Eddy Merckx
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LongJohn
recumbent guru

Netherlands
567 Posts

Posted - 06/15/2010 :  04:07:55  Show Profile  Visit LongJohn's Homepage  Reply with Quote
Nigel,

That's looking good! I can see where you are going to mount the saddle... ;-)

Depending on your cruising speed I would opt for bigger ring in front...

Thomas
(http://flevofanclub.ligfiets.net/?doc=ch4-02&lang=en see: photo's lowracers for my old bike)
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25hz
human power supergeek

Canada
1223 Posts

Posted - 06/15/2010 :  04:26:07  Show Profile  Visit 25hz's Homepage  Reply with Quote
That's a slick looking beast. I don't know what it is, but I really like black on a recumbent, especially semi gloss or flat.

Maybe I have the demographics wrong, but it's interesting how different areas seem to have different design favorites. There seem to be a ton of Frenchmen preferring the swingboom/Flevo style. Lots of Germans and northern Europeans like to build Pythons. Australia likes trikes. Southern US seems to prefer highracers, while the mid northern US and the racing in Europe seems to prefer lowracers. I guess things in the Netherlands will slowly switch over to mid racers?
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nigel schroder
recumbent enthusiast

New Zealand
190 Posts

Posted - 06/16/2010 :  00:57:53  Show Profile  Reply with Quote
quote:
Originally posted by LongJohn

Nigel,

That's looking good! I can see where you are going to mount the saddle... ;-)

Depending on your cruising speed I would opt for bigger ring in front...

Thomas
(http://flevofanclub.ligfiets.net/?doc=ch4-02#12296;=en see: photo's lowracers for my old bike)



How big do you think I need to go

"It never gets easier, you just go faster."- Greg LeMond

"Don't buy upgrades; ride up grades." - Eddy Merckx
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LongJohn
recumbent guru

Netherlands
567 Posts

Posted - 06/16/2010 :  01:50:39  Show Profile  Visit LongJohn's Homepage  Reply with Quote
Nigel,

See; http://www.sheldonbrown.com/gears/

Here you can calculate your speed @ different rpm with a certain gear set-up. Depending on your goal speed (sprint, hour race, criterium, etc), you can determine set-up.

Thomas
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nigel schroder
recumbent enthusiast

New Zealand
190 Posts

Posted - 07/20/2010 :  11:08:33  Show Profile  Reply with Quote
here you go .What do you think?
http://www.youtube.com/watch?v=FG5okNSvpTY

"It never gets easier, you just go faster."- Greg LeMond

"Don't buy upgrades; ride up grades." - Eddy Merckx
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LongJohn
recumbent guru

Netherlands
567 Posts

Posted - 07/20/2010 :  11:48:56  Show Profile  Visit LongJohn's Homepage  Reply with Quote
Love it!

I like the handlebar setup. Do you use SRAM or Shimano?

Thomas (who wants to start his own project but has to be patient)
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nigel schroder
recumbent enthusiast

New Zealand
190 Posts

Posted - 07/20/2010 :  12:34:55  Show Profile  Reply with Quote
quote:
Originally posted by LongJohn

Love it!

I like the handlebar setup. Do you use SRAM or Shimano?

Thomas (who wants to start his own project but has to be patient)



A bit of both,depends on what I've managed to find.

"It never gets easier, you just go faster."- Greg LeMond

"Don't buy upgrades; ride up grades." - Eddy Merckx
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DocBB
Starting Member

France
18 Posts

Posted - 07/20/2010 :  21:47:53  Show Profile  Reply with Quote
quote:
Originally posted by nigel schroder

Just need to add a seat and handlebars.

What do you think?






some new pics?
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nigel schroder
recumbent enthusiast

New Zealand
190 Posts

Posted - 07/20/2010 :  22:47:04  Show Profile  Reply with Quote
quote:
Originally posted by DocBB

some new pics?






Did you have a look at the Video
http://www.youtube.com/watch?v=FG5okNSvpTY

"It never gets easier, you just go faster."- Greg LeMond

"Don't buy upgrades; ride up grades." - Eddy Merckx

Edited by - nigel schroder on 07/20/2010 22:47:25
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nigel schroder
recumbent enthusiast

New Zealand
190 Posts

Posted - 07/24/2010 :  14:21:26  Show Profile  Reply with Quote
Well the roll down didn't quite go as well as planed.

1st run the bike was faster

2nd run things went a little wrong , I crashed at about 50-55kph. Fell from the bike and slide down the road a little then into a creek hitting some very larger rocks on the way ,my helmet was completely destroyed. I got up and James drove me home ,then we went to the hospital ,where I spent the next 7 hours being checked. X-rays and a CT scan. Luckily nothing was broken.
Feeling very sorry for myself today.

As for the bike it's ok but it's the last time I'll ride it as a moving bottom bracket, it'll get a rebuild and have a boom added.

"It never gets easier, you just go faster."- Greg LeMond

"Don't buy upgrades; ride up grades." - Eddy Merckx
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warren
human power expert

4795 Posts

Posted - 07/25/2010 :  06:58:03  Show Profile  Visit warren's Homepage  Reply with Quote
Wow, sorry to hear that, I'm happy that you made it through that crash without serious injuries.

What happened on the coastdown, or did it happen too fast to tell? My guess is that all was going fine until you decided to pedal.

I'll be interested to see the fixed boom rebuild!
-Warren.
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DocBB
Starting Member

France
18 Posts

Posted - 07/25/2010 :  09:29:29  Show Profile  Reply with Quote
Too bad I'm sorry for you I hope you'll get better soon.

and if you really want to get rid of the bike , would you sell it to me?
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