parksanghyun

~Hi. How are you?
Im a high school student in Korea.
I designed a recumbent bicycle for me.

Its not done yet but Could you do some reviews about my stuff? Such as problems, weakness or else.

Thank you so much.
regards.

andr0id

Your design is really cool.

I suspect it is way over built and would be VERY heavy if you actually made one.
You should look at slimming it down some.
Recumbents for the road rarely have shocks.

Wanderer

Where is the locomotion?

fietsbob

its a quad not bi .. cycle off road quads are on the market already Off road capable for wheel chair using folks ..


search out existing tested and functional designs and compare them with your animation.. on the Web.

they have suspension knobby wide tires and disc brakes I see no brakes ..and the suspension is out of scale

and paved roads, wheels wont really need to have suspension .

'Tadpople' Recumbent trikes dont need a rear differential , As they only drive 1 wheel .. lighter simpler etc.

RonH

Where are the pedals and the chain to drive the wheels? I agree it looks very heavy.

Sullalto

Odd place for suggestions, but there's some similar examples here: LocostUSA.com ? View topic - Recumbent four-wheel bike
I'd look up monoshock designs on that same site as well.

BobbyG

Yes, on the one hand your design may not be practical. But on the other hand, your work shows imagination, drive and your talent as a young engineer. And the fact that you are asking for advice leads me to believe that you may create some stellar designs in the future. Best wishes for future success!

alcjphil

Bicycles have 2 wheels. I see no drivetrain. You have concentrated on suspension and have ignored how the "bike" will be driven. There does not appear to be enough space at the front end for a driver to turn some sort of pedal system

GravelMN

From a safety standpoint, your front frame and suspension design is major injury waiting to happen. Unless the rider was restrained even a minor front end collision would result in serious groin and leg injuries.

Your frame and suspension are way overbuilt for a non-motorized vehicle.

james_v

Appears overly complicated and heavy for a human powered vehicle. Sometimes less really is more.
Good luck on your endeavor though.

BlazingPedals

I don't see a bicycle, or even a quad-cycle. There's no place for pedals, no line for a chain, and I can't see how you expect to power any of the wheels. The only way that thing will go down the road is with the help of a 10-hp engine. Which also isn't in your plans. I suggest you start over from scratch.

parksanghyun

wow!! Thank you for comment! ㅠ_ㅠ!! i am not good at english, but veryvery thankyou!! ㅠㅠ

Homebrew01

If you don't want to balance like a bicycle, just use 3 wheels a save a lot of weight.

avidone1

If it has four wheels it's not a bicycle.

Looigi

Other issues aside, there are some significant structural issues, like very little longitudinal torsional rigidity and bending rigidity in the area of the seat. Also, connect the tops of the left and right shock towers together.

Garfield Cat

Yes, rarely have shocks, until I saw Eric in Santa Barbara near UCSB with his Scorpion. Its a trike recumbent, fold-able, shocks, disc brakes, etc.

HP Velotechnik - Products - Scorpion fx - Details foldable recumbent trike

rex615

Suspension Geometry; I can't really tell from the pics but when using A-Arm suspension (as you have), the established practice is to make them unequal length. The top arms should be shorter so that as the suspension compresses the wheels will increase in negative camber which increases stability.

If the suspension is compressed as the result of a turn (because of body roll) negative camber will generate camber thrust in the correct direction to aid with turning. In a turn the outside wheels mater most because they are the ones that bear more weight. Your design appears to generate positive camber, which will make handling in turns less than optimal.

Your steering arrangement seems to have adequate Akerman compensation and sufficient steering axis inclination, so that part is good. Bear in mind that in Human powered vehicles, toe-in has to be set to nearly zero in dynamic condition because tire scrub wastes power and quickly wears out bicycle tires.

Your rear rear end with independent suspension (not really required on this type of design) will require 2 constant velocity joints or at least 2 universal joints on each side, This is heavy and overly complex. Consider using a straight axle if you must stick with a 4 wheel design, or better yet, consider the much simpler single rear wheel which others have suggest.

wphamilton

Your suspension is a kind of fascinating engineering problem and I'd need a deep dive into steering/suspension tech (in the direction of @rex615) before I'd comment. However, from a practical point of view there is one big issue that I'm worried about. That much suspension is going to rob you of pedaling power unless you're on a smooth road, which may defeat the purpose. If it were my project I'd be inclined to simplify the suspension and then try to design it with the drive mechanism in place.

shelbyfv

What's the scam here? I see we have another "student from Korea" with a similar post. Are they mining data somehow? There aren't links to click on. Seems a waste of their time but I don't know much about internet scammers.

rex615

Agreed that the OP's suspension design is overly complex. In an upright bicycle, suspension will often cause a "pogo" effect and the better systems have a lockout for climbing. However, suspension does not cause the same issue on a recumbent, particularly trikes. The smaller wheels often used on them benefit from suspension, plus the recumbent rider can't just stand on the pedals to use his legs as suspension.

Both of my velomobiles have full suspension, albeit with a McPherson strut style, which is lighter and simpler, plus allows the the pilot to sit between the front wheels. (which is paramount on a tadpole for tipover resistance)

rex615

I saw that one, huge rack and pinon steering with no support on the pinon, but don't get me started.

At any rate it seems more like legitimate projects, with the students wanting us to do their homework for them. But i am very gullible, so who knows.

wphamilton

I wouldn't gainsay any of that! But he has big wheels and it looks mushy. Granted that could just be optical on my part and overcome in the details.

BlazingPedals

A quad cycle is nothing more than a delta trike rear end and a tadpole trike front end. It's usually done by starting with a tadpole trike and adding a conversion kit to the rear. Doing it as an add-on has several advantages, including it's easily removable for maintenance, and it can easily be converted back to a tadpole trike. The most complicated mechanicals are in the front end, where the proper geometry has to be designed in (trail, kingpin angle, ackerman, etc.) I suggest you get your initial inspiration from existing products and see if you can improve on them. Remember that custom cut gears are expensive to manufacture, whereas bearings and ball joints are not; and suspension is a luxury that has a weight penalty associated with it.

Utah Trikes - Candy Red TerraTrike Quad

CroMo Mike 

A legitimate question. hmmm!