Plans on getting bent [Archive]

Brian

07-03-05, 03:36 AM

The urge to tinker is leading me down yet another path. I'd like to build a 'bent, specifically a tadpole. Does anyone out there have have plans for one? Either electronic or on paper. PDF would be best of course. I'm also happy to accept advice anyone has to offer. I've got a pretty good idea of what I want as far as a commuter with 20" tires, but I'm looking to go with the best features of all the current designs out there. All help is appreciated.

jeff-o

07-03-05, 08:48 AM

http://www.greenspeed.com.au/plans.htm

http://www.greenspeed.com.au/NewGSweb/web-content/usa/plans.html

http://www.ihpva.org/com/PracticalInnovations/

http://www.hellbentcycles.com/Design_Overview_R1.htm

Those should get you started!

Brian

07-03-05, 02:39 PM

Thanks. I've been to those sites, and a few others. I'm looking for the actual plans, with some advice on which steering system works best, and other technical details. Greenspeed charges AU$150 for their plans, which is a bit much for a bike I'm not going to build. If anyone has photos of one they've built themselves, please post them here.

Thanks again.

Brian

07-04-05, 04:41 AM

Oops! Looks like I missed something on previous visits to the ihpva website. Those plans certainly provide a good starting point. Thanks yet again.

jeff-o

07-04-05, 05:57 AM

So... can you weld aluminum? I want to build one too, but do not yet possess the skills...

Brian

07-04-05, 02:41 PM

So... can you weld aluminum? I want to build one too, but do not yet possess the skills...

I can, but will be building it out of steel. It will be much easier to fabricate, then modify.

jeff-o

07-04-05, 02:47 PM

I can, but will be building it out of steel. It will be much easier to fabricate, then modify.

And it'll weigh a zillion pounds. Well, more like 50+.

Fine, build a prototype out of steel, then build the final product out of aluminum.

Brian

07-04-05, 02:58 PM

And it'll weigh a zillion pounds. Well, more like 50+.

Fine, build a prototype out of steel, then build the final product out of aluminum.

It won't weigh near 50lb. And if I wanted light, I'd have it made out of titanium to match our tandem. But wieght is not a major consideration on a recumbent trike, so it doesn't matter.

Brian

07-05-05, 01:03 AM

That, and the fact that I have a stocky Russian build and weigh around 200lbs. Not only will I not worry about a bit of extra weight on the bike, but aluminum will probably have a short life span under me.

Anyone care to offer opinions of different steering options? And is 9x27 enough gears, or is a 3 speed hub an option as well?

jeff-o

07-05-05, 05:47 AM

Reconsider titanium: www.titaniumjoe.com

Overstock titanium tubing, bars, plates, sheeting. Depending on the alloy you get, you may not have to heat-treat it. At least, I think that's right. You will need an argon gas TIG welder though.

Brian

07-05-05, 02:56 PM

I wouldn't weld my own titanium - that's asking for trouble. That's also what builders are for.

jeff-o

07-06-05, 05:57 AM

I wouldn't weld my own titanium - that's asking for trouble. That's also what builders are for.

Aw, how hard can it be?

Really, I want to know, how hard is it to weld titanium?

Brian

07-06-05, 06:04 AM

Aw, how hard can it be?

Really, I want to know, how hard is it to weld titanium?

Easy. Unfortunately, the welds are extremely susceptible to contamination, and will quickly fail if the surfaces are not prepared properly and completely free of any foreign matter. I'm not sure what kid of gas shielding is used as well, but for myself, the risks and the trouble outweigh the benefits by a wide margin.

jeff-o

07-06-05, 06:56 AM

Ah, yes, you have to clean the weld points thoroughly, and you need an argon gas shield while you're welding. But other than that, it's easy?

The reason I'm asking is that I will soon be taking a welding course myself, with the intent of starting up a new hobby. Eventually I want to build my own trike, and I want to build it out of titanium. Why titanium? Well, because virtually no-one else has a titanium trike, that's why. ;)

Brian

07-06-05, 07:02 AM

jeff-o

07-06-05, 08:20 AM

No one has one made out of Jello pudding either. :D I just don't see weight as being an issue with trikes.

Weight of trikes is just as much an issue as weight of bikes. The lighter it is, the more energy you can put into making it go faster, rather than overcoming inertia.

So... a jello trike, eh? Do you have to freeze it to make it solid? ;)

steveknight

07-06-05, 10:16 AM

a good place to hang out http://www.bentrideronline.com/messageboard/forumdisplay.php?f=12

Brian

07-06-05, 02:55 PM

Weight of trikes is just as much an issue as weight of bikes. The lighter it is, the more energy you can put into making it go faster, rather than overcoming inertia.

So... a jello trike, eh? Do you have to freeze it to make it solid? ;)

Aerodynamics play a bigger role than weight.

bentrox!

07-06-05, 03:54 PM

Aerodynamics play a bigger role than weight.

Not on a long, steep hill - but then trikes can negotiate just about any hill regardless of weight as long as the gearing is there and you don't mind a s-l-o-w climb.

steveknight

07-06-05, 09:34 PM

Aerodynamics play a bigger role than weight.
only when you get going pretty fast. on flats weight is not as much of an issue. but hills it is a far bigger one. once you get about 20mph and over then Aerodynamics starts making a bigger impact.

Brian

07-07-05, 03:57 AM

only when you get going pretty fast. on flats weight is not as much of an issue. but hills it is a far bigger one. once you get about 20mph and over then Aerodynamics starts making a bigger impact.

Math time. I weigh around 200lb, as stated above. If aluminum saves me 4lbs, I'll have 2% less weight to haul up a hill. It won't cost anything extra to lose that weight off the rider, whereas it's not cost effective to take it off the bike. Although I imagine that there's enough places on the bike where I could save a significant amount of weight by using things like my spare XTR cassette, and all the ti and aluminum hardware I have. I'll do a cost/benefit analysis for all the little bits.

Question for bent riders: Is it as easy to maintain a high cadence/high gear in a reclining position?

JohnH

07-07-05, 08:46 AM

Question for bent riders: Is it as easy to maintain a high cadence/high gear in a reclining position?

My 'bent experience is limited to SWB's with fairly high cranks. For me, shorter cranks (155mm vs. 170mm) are necessary on the 'bent to feel like I'm spinning smoothly. I only have about 500 miles on the bent vs. several thousand on the DF, so this might have gone away over time. In the end, I don't really care because I'm spinning 5-10 rpm faster with the same perceived effort, and my max effective cadence has increased at least 10 rpm. I'm not strong enough to *maintain* both high cadence and high gear - but that's a fitness issue. As I'm getting stronger, my sense is that it's not harder, just different. I find I can "lock in" to the seat back and really focus on pushing with quads/pulling with hamstrings. I actually *feel* as though I'm generating more power this way than I can generate *in the saddle* on a DF, and since I never got out of the saddle for more than a few pedal strokes, that's a fair comparison for me. No Powertap, so I can't quantify this at all.

Hope this helps,

jeff-o

07-07-05, 11:06 AM

I suppose I'm more conscious of bike weight since I ride almost exclusively in the city, where I have to start and stop frequently. And, the difference between some steel and aluminum trikes can be up to 20 pounds. For instance, the cheaper trikes weigh 45-50 pounds, where decent trikes (like the Catrike Speed) weigh only 29 pounds. That's a big difference, and one that you'd be sure to notice.

Brian

07-07-05, 02:34 PM

jeff-o

07-08-05, 06:14 AM

John, thank you, that does help. I can no longer get comfortable on a road bike for extended periods, but I've got the legs to get me going on a recumbent. I guess my concern was losing efficiency compared to a DF.

Jeff, my MTB tandem doesn't weigh 40 pounds. Do you think I'll let a 20" wheeled trike blow out to some ridiculous weight? :D

Yeah, I was thinking of that Sun trike (I think it was Sun). Build with enough steel for two trikes, it was. I laughed when I read the specs for it, then closed the browser tab.

Brian

07-08-05, 07:56 PM

Ok, as I start to assemble my parts list, I've got some questions. I may have to start a new thread if I don't get enough repsonses here.

Rims. I'm partial to Sun rims, particularly the Rhyno Lites, but they're porbably not the best choice for a recumbent. I notice Alex describes their X-101 and DA16 as "Excellent for recumbents". Can anyone offer their opinion, along with the reason they would choose one over another?

Hubs. I'll probably go with Shimano XT disc out back. I'm wondering what most people use up front though. I like the 20mm thru-axle front hubs, but that may be overkill.

Brakes. Again, I'm partial to Magura, but leaning towards Hayes, as there's a handy 2 into 1 adapter that will let me run both front hydraulic discs off one lever. Suggestions?

Shifters. SRAM appears to be the standard, due to their twisty grips. Do I go with X.9, or does someone else have a suggestion?

Thanks.

jeff-o

07-08-05, 09:05 PM

Also look at Avid disc brakes, and drum brakes.

Aside from grip shifters, the only other shifters I've seen are bar-end shifters. I wonder if it would be possible to attach rapid-fire shifters to a recumbent's vertical handles?? I think they'd have to be about 1.5" longer than normal for mounting, and perhaps bend inwards slightly.

Brian

07-08-05, 09:14 PM

I've got some Avids, but I've only seen the 2 into 1 for Hayes. Bar end shifters would be a step backwards in technology.

jeff-o

07-08-05, 10:11 PM

I've got some Avids, but I've only seen the 2 into 1 for Hayes. Bar end shifters would be a step backwards in technology.

There are some trike manufacturers that use Avids and their own 2 into 1 cable system. Are you trying to avoid brake steer? I'm not so sure that an extra few pieces of metal would be any better at eliminating brake steer than two human hands. Though, you would be able to brake with one hand.

From what I've read on these forums and other places, some people prefer the bar-end shifters. One rider even replaced the grip shifters with bar-end shifters. How easy is it to downshift and brake at the same time with grip shifters? It can be done with bar-end shifters...

Brian

07-08-05, 10:55 PM

Fluid pressure will provide the equal braking that a cable system can't. I can get a lever that pulls two cables, or even make something that allows the the cable to run two mechanical brakes, but it will never be as simple as dual hydros.

I was hoping someone with actual experience with the shifters would offer their advice. By running the front brakes from the left lever, and shifting the rear gears from the right grip, I've eliminated the brake/shift worries.

geebee

07-09-05, 06:42 AM

Bar ends are IMO the best on a trike, with the way the handle bar sits in your hand they are in a perfect position to use and you can get a feel for which gear you are in,
I have ridden a trike with twist grip shifter and wasn't impressed (this was before I got the GT3 with bar ends, so I wasn't predisposed toward bar ends).
Normal setup brake wise for a trike is a lever on each handle for that side front wheel, rear brakes aren't required (under heavy braking there will be negligable weight on the back wheel, thus it will lock up easily and not help greatly) and if fitted should have the lever some where it won't get grabbed by mistake as it can cause a trike to swing sideways and flip.
I have read of several mechanical setups with brakes linked to a single handle and I think Green Speed sell a suitable handle.