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PeterSibley
06-23-2012, 06:17 PM
http://mark.rehorst.com/CF_Bike/index.html

There's some really good information here, especially for those not familiar with carbon fibre... like me .:d

Keith Wilson
06-23-2012, 08:19 PM
Man, it sure seems a lot more work than old-style brazed steel tubing. I built a long-wheelbase recumbent in 1981; 16" front wheel out in front of my feet, under-seat steering with a link rod. It was lots of fun, and recumbents were so rare at that time it would attract way more attention than I wanted; sort of like driving a purple metalflake Lamborghini. I don't have an electronic picture, but it looked sort of like this, except I used a single large-diameter tube for the front part of the frame.


http://www.legslarry.beerdrinkers.co.uk/images/mags/large/Avatar01.jpg

The Bigfella
06-23-2012, 09:34 PM
Having dabbled with carbon fibre (and kevlar) to make some bits for my KTM... I have to say, its a lot more work than I'd anticipated. My son had a bit of experience with it on the university race car team... and he reckons its the "next asbestos" from an OH&S perspective.

Ducati... who are having problems with their MotoGP bike are finding CF may not be the answer. Its taking them a month to work up a frame change in CF.... where other teams just crack on the TIG

PeterSibley
06-23-2012, 11:51 PM
I think you might be right Ian but if you don't sand it , just epoxy it on things might be safer ? (I assume you are talking about micro fibres in the air ? )

The Bigfella
06-24-2012, 03:59 AM
You can't avoid sanding / cutting it though Peter. To get its best properties happening - you need to be vacuum bagging (and autoclaving)

PeterSibley
06-24-2012, 04:03 AM
Can you just cut it with shears?

The Bigfella
06-24-2012, 04:12 AM
An angle grinder with a thin blade works. Shears work... until you add the epoxy

Curtism
06-24-2012, 04:43 AM
To add to what Ian mentioned, dont cut/grind the hardened fibers in enclosed areas with electric tools, or anything that makes an open spark, as carbon fiber dust can be highly flammable in the right concentrations. Use pneumatic tools.

PeterSibley
06-24-2012, 04:47 AM
To add to what Ian mentioned, dont cut/grind the hardened fibers in enclosed areas with electric tools, or anything that makes an open spark, as carbon fiber dust can be highly flammable in the right concentrations. Use pneumatic tools.

Noted, thank you. I think I'm tending back to steel tube and brazing ! I know how to do it and it's fast.

AussieBarney
06-24-2012, 05:34 AM
Peter, why complicate things, or are you trying to be as space age as you can get. Remember the model T ford. It's very basic engineering, but guess wot? It works, quite often where modern technology will break down. and we won't even start discussing cost.

PeterSibley
06-24-2012, 05:52 AM
It's an interesting site Barney , I guess I got introduced to the idea by a mate would build radio controlled gliders. Lovely things that need to be strong to resist very fast landings on occasional .

Mate, the reality will probably be brazed steel tube and this design. A Bentech.

http://pic40.picturetrail.com/VOL282/9443996/17245530/403159815.jpg

The Bigfella
06-24-2012, 07:56 AM
But why?

... and how come the photos never have the flag they need so that cars might actually spot them?

The Bigfella
06-24-2012, 07:58 AM
Sorry... just realised the answer to my own question... less ED issues this way.

PeterSibley
06-24-2012, 08:00 AM
These bikes aren't that low Ian, there are some very (frighteningly ) low ones but this one isn't . It's all about the bike seat or lack thereof.

The Bigfella
06-24-2012, 08:01 AM
These bikes aren't that low Ian, there are some very (frighteningly ) low ones but this one isn't . It's all about the bike seat or lack thereof.

Um, yes... what I said.

Where's Stevebaby in all this?

Paul Pless
06-24-2012, 08:41 AM
Its not a very 'elegant' design. To me at least, besides its lightweight strength, one of the most attractive attributes of designing/building in carbon fiber are the ability to create lithe, flowing, organic, and cohesive designs. In the end this looks like a couple of two x fours bolted together with hardware store fasteners and then painted black. Every attachment point looks like an after thought.

http://mark.rehorst.com/CF_Bike/bike_right.jpg

Compare to these. . .

http://www.rqriley.com/imagespln/xr2-1.jpg

http://steampunkworkshop.com/userfiles/image/nocomside.jpg

http://www.recumbents.com/wisil/racing2007/northbrook-kenosha/hunn/Gary%20Toy,%20riding%20a%20carbon-fiber%20Cobra%20FWD%20lowracer,%20%20tries%20to%20 whistle%20a%20happy%20tune%20to%20take%20his%20min d%20off%20the%20pain.jpg

http://www.bentrideronline.com/wordpress/wp-content/uploads/2009/05/zockra.jpg

The Bigfella
06-24-2012, 09:25 AM
Now you're cooking with gas

The Bigfella
06-24-2012, 09:30 AM
Just on CF... I've been amazed at its ability to take punishment. I've had big fat chicks sitting on my CF/Kevlar rack and its taken it. I've cartwheeled the bike and hit the headlight carrier... and its taken it. The only failure I've had is on constructed sections that weren't laminated together... where the joint has failed. Prototype 2 won't fail

Gerarddm
06-24-2012, 10:36 AM
I have never understood the rationale for these things other than to avoid a prostate-crushing conventional seat on a standard frame; but to me any possible advantage is more than outweighed by a scary lack of visibllity
( from other drivers ) and lack of emergency maneuverability.

Old Dryfoot
06-24-2012, 01:12 PM
I do like recumbent bikes but I'd have to say that my preference would be for a tadpole or a delta trike of some sort. The one thing about them I don't like however is the visibility factor, or lack of I should say. One with a higher seating position would would be ideal for me.

Not as sexy as a sleek, low riding trike, but it seems a lot safer on a crowded street.
http://atomiczombie.com/plans/deltarunner/DeltaRunner%20Recumbent%20Delta%20Trike%207.jpg

Peter, have you come across the Atomic Zombie web site (http://atomiczombie.com/default.aspx) yet? Lots of plans, not that I think you'll need them, but you might find some inspiration.

Old Dryfoot
06-24-2012, 01:25 PM
I have another link for you, this one is quite a detailed account of the construction and design process involved in building the Thunderbird recumbent. Lots of good info on materials, design considerations, as well as suspension and steering geometry.

(http://http://www.ihpva.org/Projects/PracticalInnovations/index.html)http://www.ihpva.org/Projects/PracticalInnovations/index.html

http://www.ihpva.org/Projects/PracticalInnovations/t_bolt4.jpg

2MeterTroll
06-24-2012, 01:27 PM
visibility i will grant you in some ways but maneuverability i wont. I can bunny hop my trike and spin it in less space than an upright. then you have the speed part and that just blows uprights out of the water.


I have never understood the rationale for these things other than to avoid a prostate-crushing conventional seat on a standard frame; but to me any possible advantage is more than outweighed by a scary lack of visibllity
( from other drivers ) and lack of emergency maneuverability.

wharf rat
06-24-2012, 02:42 PM
I have never understood the rationale for these things other than to avoid a prostate-crushing conventional seat on a standard frame; but to me any possible advantage is more than outweighed by a scary lack of visibllity (from other drivers ) and lack of emergency maneuverability.

For many people, they're easier on the back. Many people who have back issues have found them comfortable--even diamond frame riders who have to give up riding their conventional bikes.

You have better visibility as a rider because you're looking straight ahead rather than downward. It's a better defensive driving position, actually. No stiff neck on long rides.

With the exception of the lowest, most recumbents put you up high enough to be seen by most traffic. Flags and such add to your visibility.

Easier to ride into the wind--which is why they hold so many speed records. On a diamond frame you're pushing a lot of wind.

As for maneuverability, the hottest trend in mountain biking is recumbent mountain biking. These bikes are going many places and under the same conditions as the other off-roaders. They're pretty maneuverable.

As for building you own. I've never owned a long wheel base, but I'm collecting parts for one of these: https://sites.google.com/site/recycledrecumbents/home

I've thought about making one in CF, make a bunch of CF tubes then assemble them. But then again I'm also considering the feasibility of doing it in bamboo, too.

Keith Wilson
06-24-2012, 04:50 PM
I have never understood the rationale for these things other than to avoid a prostate-crushing conventional seat on a standard frame; but to me any possible advantage is more than outweighed by a scary lack of visibility (from other drivers ) and lack of emergency maneuverability.I rode mine quite a lot before I got old and lazy, and I can give you a fair idea of the advantages and disadvantages. This applies to roads and very moderate trails: I never tried anything else.

Advantages of the recumbent:
- Comfort. No contest at all, and the difference gets greater the longer you ride. With even the best ordinary bicycle seats, there are only degrees of discomfort - mildly unpleasant to excruciating. A recumbent seat can be as comfortable as the best chair. In addition, there's almost no weight on one's arms and hands. Yes, you can get used to a standard bicycle, and some are perfectly OK for moderate distances.. God save us from what we can get used to.
- Stability/safety. At least with the low long-wheelbase bikes, even with quite narrow tires, one doesn't even notice gravel and road hazards that could cause serious trouble with a standard bike. I didn't expect this at all; it was quite surprising. And if you do fall over, it's a gentle slide to the ground landing on your side, not a fall on your head from high enough to do damage. Pitching over the front wheel is impossible.
- Wind resistance. In conditions where wind resistance is the limiting factor, recumbents are very significantly faster. There's an excellent reason they ban them in racing. Especially when combined with greater stability, this makes long downhills a total blast.

Things that are about a wash:
- Overall speed. At least for someone of my quite moderate athletic ability, speed overall didn't seem to be much different. The bike seemed slower up hills, faster down. I'm not sure why climbing should be slower; perhaps it has to do with not being able to put one's weight over the pedals.
- Visibility (the rider seeing things). You're lower down, but your head is upright. Six of one . . .

Disadvantages of the recumbent:
- Visibility (Other people seeing you): Gotta have that flag in traffic. It's as essential as air in the tires.
- Low-speed maneuverability. At least with the long wheelbase, this is a real disadvantage. OTOH, greater stability partially compensates. You can always put your feet down and point the bike where you want it to go, but the standard bike is much more maneuverable at a walking pace. At higher speeds, there's not nearly so much difference.
- Transporting the bike when you're not riding it. Recumbents are big and awkward by comparison.
- And last but not least, with under-seat steering there's no airflow over your armpits. This can get seriously unpleasant on hot days.

PeterSibley
06-24-2012, 06:05 PM
I do like recumbent bikes but I'd have to say that my preference would be for a tadpole or a delta trike of some sort. The one thing about them I don't like however is the visibility factor, or lack of I should say. One with a higher seating position would would be ideal for me.

Not as sexy as a sleek, low riding trike, but it seems a lot safer on a crowded street.


Peter, have you come across the Atomic Zombie web site (http://atomiczombie.com/default.aspx) yet? Lots of plans, not that I think you'll need them, but you might find some inspiration.

Thanks for the links , some of the instructional stuff is useful but when it comes to design I'll go for a swb underseat steer, I love the simplicity of the things!