Comments on: DuoCycle trike

By: station44025

station44025 — Sat, 09 Jul 2011 20:59:58 +0000

It appears the person in the front seat’s handicap is abnormally stunted legs. Anyone bother to check how far in front of the seat the bottom bracket is on a tadpole? Doesn’t look like it.

By: Mike

Mike — Mon, 06 Jun 2011 22:36:11 +0000

I don’t think so, look at the pivot directly under the front rider’s spine in some of the renderings on the web page, as well as the skinny axle that connects the two wheels.

By: Noah

Noah — Fri, 03 Jun 2011 20:30:24 +0000

It looks as if this tadpole tricycle is using a steering linkage. Ackermann steering geometry allows for stable tricycle steering that works beautifully on tadpole tricycles - in fact, I built a prototype tandem tricycle very similar to this one about a decade ago. link.

By: Mick Allan

Mick Allan — Fri, 27 May 2011 12:04:49 +0000

Wow – way to target a tiny niche within the smallest sector of cycle sales: Disabled people who can pedal

Speedy make a machine for this market. http://www.cyclorama.net/viewProduct.php?id=104
Understandably they don’t make very many.

And hubless wheels? The current craze in student design portfolios all over the world. Yawn. Imagine what a side load might do to the mechanical drag of the bearings and the structural integrity of that unsupported rim…

Lets face it – these things are nothing more than styling/thinking exercises and rendering practice.

By: Mike

Mike — Thu, 26 May 2011 20:05:59 +0000

This guy should build a prototype. As soon as he tries to make it turn he will see the problems with geometry of the steering. See http://www.dclxvi.org/chunk/meet/multiwheel/index.html at which is documented:
“The Stupid Tadpole Trike.
This one was designed by someone who didn’t bother to do a little experimentation before heating up the torch. Hint: on a reversed trike with a non-vertical head tube, watch how the frame leans when the handlebars are turned. It can be ridden, but only Big Bear can ride it for any distance, and that’s just because Big Bear can ride anything. Basically, one of the front wheels is always off of the ground, and whichever one it is, it will be down and the other one will be up a moment later.”

So yeah, this design has a fatal flaw that could have been discovered instantly with a little prototyping. But who wants to prototype when there are fake computers that will never be built to be rendered?

By: Andy

Andy — Thu, 26 May 2011 19:03:40 +0000

If he is able to comment, these are the things missing enough explanation:

1) Hubless wheel might shorten wheelbase, but as such a manufactured product does not exist currently, it renders this unfixable by any bike shop, the user unable to change a tire or fix drivetrain issues, and allows for more potential issues if the drivetrain is out of alignment. So shorten the wheel base by using a hubless wheel introduces many new problems with only one slight benefit. A smaller rear wheel would offer the same benefit without the complications.

2) What is the battery for? The person in front can pedal, but explain the benefit. Is there a motor that helps power the bike as well?

3) Why use paired spokes? They offer aerodynamic benefits at the cost of harder to fix wheels when a spoke brakes because you can’t easily re-true a wheel one one spoke brakes. Given the overall weight of this bike will likely be over 100pounds, 18 spoke wheels with spoke pairs is a very unusual choice since I would assume this isn’t meant to ride at speed where the only benefit (aerodynamics) even comes into play.

By: Juliano Pappalardo

Juliano Pappalardo — Thu, 26 May 2011 18:53:04 +0000

Wim I agree with your concept of carrying a person that can help and has the front view free of obstacles, but the guys might be saying the truth about hubless wheel, these parts can´t be found easily and this is a very important design criteria, check this image which may be inspiring I took from the internet: http://images.quebarato.com.br/T440x/triciclo+de+carga+space+sao+paulo+sp+brasil__272480_1.jpg

I don´t realize why the wheelbase must be this short.

By: James Thomas

James Thomas — Thu, 26 May 2011 18:33:07 +0000

He does give a reason for the hubless wheel (to shorten the wheelbase), but in general the details about the concept are a bit vague. I was expecting a comment like Andy’s questioning a few of the choices. Perhaps Wim can comment and elaborate on the reason behind a few of the design decisions.

Andy, regarding your second paragraph, I think that is sort of the point of school. I am sure that the professors do ask hard questions about choices the student has made…and if it is anything like when I was in school, so do the other students. Critiques can be rough, but learning to explain the reasons behind design decisions (and learning to acknowledge when a criticism is justified) is probably the most part of the learning process.

By: Robert Peters

Robert Peters — Thu, 26 May 2011 18:14:26 +0000

Andy, Did you look at the website? It gives the reason, with which I do not agree, for the hub-less rear wheel.

By: Andy

Andy — Thu, 26 May 2011 18:08:15 +0000

Hubless wheel, powering batteries? There isn’t even a motor on the wheel or any mention of what that system is accomplishing. I’m going to go out on a limb and bet that this will cost over 5 grand, and weight over 100lbs, so good luck with your design.

I sometimes wonder what design professors do with this junk. Do they realize how impractical these designs are? It would be much more beneficial if early in the process they identified WHY they are choosing systems that offer no benefit (like a hubless wheel) before they continue on with a time wasting design.