SpicyTuna

Hello everyone,

For a school project I have to design a leveled saddle/seat for overweight and obese people (330/400lbs) for on a recumbent bike. The goal is that the saddle is 'universal' so that multiple people can use it.

I have no idea about what dimensions I should use to keep the saddle/seat comfortable for users while it also allows them to bike without problems. The backrest is not connected to the saddle/seat.

If any of you have information/suggestions/ideas, please let me know. You can also PM me.

Thanks!

Retro Grouch 

Good luck with that.

Everything on a recumbent bicycle works together so you have to consider the design as a whole when you make major changes to any single part, like the seat. In this case, I'd think that you would need to start with a recumbent trike that has a 400 lb. weight capacity. Another biggie is going to be seat height. Recumbent trikes can be difficult to get up from and I'd suspect that heavy people would have even more difficulty that weight porportional folks.

I think that, to have an effective design, you are going to have to design a whole recumbent trike.

SpicyTuna

Hi,

the seat height is adjustable and the capacity is over 400lbs

Wilbur Bud

Mesh seat on a rigid frame, with some tensioning points for adjustment. Dimensions are going to come from your human factors handbook, after you decide the various skeletal and tissue size ranges for your target maximum weight. Longbikes does one for smaller folks, probably there are others to evaluate before settling on any improvements for your design. Here are some description and pictures on the longbikes site: Slipstream details :: Longbikes

Retro Grouch 

The capacity of what is over 400 pounds?

BlazingPedals

A mesh seat may not hold 400 pounds. I'm thinking several layers of CF on either side of plywood in a sandwich configuration. Multi-layer foam, from zotefoam on the bottom, transitioning to upholstery foam on top. Sort of like EasyRacers does. As for "how big," measure some butts. Some ER bikes are rated for 400 lbs, I believe.

BTW, adjusting the seat up and down would automatically make the bike/trike a non-recumbent, as horizontal adjustment is a checkpoint. Not that it matters for the design purposes. If it's not a recumbent, it doesn't need a seatback (another checkpoint.) If it's a trike, then COG with respect to wheelbase and track will matter. Putting 400 pounds up high will make it tippy, but if you put it too low a 400-pounder might not be able to sit down in it.

SpicyTuna

The frame

Guntrainer

Check the bike for maximum weight rating. If a really big person takes a spill, they are very likely to be seriously/permanently injured. If they hit a pothole, a wheel can fail and cause them serious or fatal injury.

Don't get caught in a liability suit. Cover your assets.

FBOATSB

Firmly padded seat that does not extend forward past butt cheeks or else will cause pain/chafing to upper back side of thighs while pedaling. Don't ask how I know this Something similar to this:



P.S. please post the results of your project. Good luck!

StephenH

Scroll down to the bottom of this page (note: defunct brand):
Cycles to Fit Big and Tall Persons

SpicyTuna

Is there a seat to butt ratio for recumbent seat width?

Moe Zhoost

You can probably find published data related to the critical measurements of large people. The human factors experts have studied this for years. There is the option of grabbing a tape and asking selected subjects to allow you to do direct measurements. I'd guess that the seat measurements would then define other measurements on the bike.

BlazingPedals

There is no one-size-fits-all saddle size for average folks, and there won't be for obese people either. Measure butts and come up with a size that'll work for most.

SpicyTuna

If it was that easy I would have done that...

FBOATSB

Suggest concentrate on sit bones to do most of the "heavy lifting" and let the rest hang where it may. Otherwise a lot of pinching, chafing, soft tissue discomfort may result for anything but very short rides. That or simply measure the width of an extra wide wheel chair at any medical facility.

SpicyTuna

If if I would put the seat on an angle instead of horizontal. What effect would this have on the knees?

BlazingPedals

Putting 400+ pounds on your sitz bones is not recommended. Just like with the bike's frame, you must distribute the weight, not concentrate it on one spot. Bent and semi-bent seats can be much wider without causing chafing or pinching. Get the seat angle horizontal or even slightly nose-up so that sliding off isn't an issue, then place the pedals so that the seat doesn't impinge the back of the thighs. (A rounded lip is OK, but it'll have to handle the weight.) Some extra-firm upholstery foam might help for comfort. For bent/semi-bent, a long nose isn't really needed but a short one might help keep a rider centered (severely obese people are not likely to have good adductor muscles.)

trestlehed

If you want to go down the "sit bones" route these links might help:

Dial in fit on any perch with new WTB Saddle Fit System at your LBS - Bikerumor

Meld offers custom built saddles for all shapes and sizes - Bikerumor

SpicyTuna

for the seat width for someone between 400-600 pounds. would you suggest 21 inches or 24?

dabac

The knees are mainly concerned with the distance between hip joint and pedals.
Any configuration that allows for the right amount of leg extension would most likely keep the knees reasonably content - assuming a rider who knows his/hers limits WRT how hard/fast to turn the pedals.


There are other geometric factors you need to consider.
Like where will the thigh go when the leg is going through its range of motion?


Roughly, there's a limit on how low the pedal can be allowed to go WRT a "reference plane" through the seat.
If the pedal drops too low, the rear of the thigh will be pushed into the edge of the seat at every stroke.


Tilting the front of the seat up means that the pedals have to go up.
The higher the pedals go off the ground, the more awkward it feels to get the bike going IMO.


Tilting the front of the seat down allows you to bring the pedals down. But I'd be concerned about feeling like I was about to slide off.


Look, why don't you stop theorizing and start experimenting?


Buy something like this:https://www.sport-thieme.co.uk/Thera...rs/art=2151104


Odds are, you'd be able to find some used. People tend to get bored of home exercise stuff like this very quickly.


Put it in front of a kitchen chair or something. Start pedalling. How does it feel after 10-20-30 minutes? Get some bricks, thick books, stacks of boards etc. Anything that'll allow you to raise the pedals several inches. Pedal some more.
How does it feel now?


Try another chair.


Build some own.


If you want flat surfaces, anyone who has ever built a soapbox racer with a backrest ought to be able to build you some prototype seats out of 3/8" or 1/2" plywood within an hour. Maybe even hinged, to allow for further experimenting.


Learn what works for normal weight people before venturing into obese territory.

BlazingPedals

Never having been 400-600 pounds, I don't know. That's where you have to do some homework.

StephenH

Go down to the local mall, ask somebody, "Excuse me sir, you appear extremely obese, may I measure your butt?"


How bout this: Go look at the seats on mobility scooters.

Moe Zhoost

Do some searching for "anthropometry" or "anthropometric measurements" and obesity. There are a bunch of studies that publish data that you could probably use.

Also, you need to account for an arrangement so the pannus is out of harm's way. Hard to pedal when it is in the way, and you certainly don't want it to drag on the ground.

osco53

Heeer ya go

SpicyTuna

whats the capacity of that bike?