Seat angle tests - is 90 too steep?

From graham butler: 

I have attached pictures of the seat with the 3 angles that we talked about.

Conclusion:  sitting on it 110 is definitely a nice low rider position.  With this particular handcycle I end up too far from the cranks.

I definitely want to be more upright for high rider.  90 is too upright, but I think that 95 will be quite comfortable for high rider.  It feels upright enough to be good for interacting with people.

Seat Angle Dimensions

[From Graham Butler February 16, 2011

Here are the screen shots of the seat vs base measurements.  SolidWorks takes the smaller angle as default to the actual seat angle is 180 less the measurement.

 

We're worried that the seat angle is too acute in high rider mode.

Low rider mode seat angle is 109 degrees, same as Bobby Hall bike.

Moved Seat Cross Member Forward to Eliminate Interference

[January 29, 2010 From Graham Butler:]


My approach with the seat was to keep it simple.  I just moved the cross member forward until it did not interact with the main frame.   The simpler the design the less chance there is that we will have problems with flex and failure.  I think that if bottoming out is an issue, then we should consider raising the seat rails to give more clearance, or consider a solid seat.

(Editor's note: the cross-member in the middle of the seat bottom was going to hit the main tube when you morph down. Graham moved it forward. This still gives sufficient strength, but eliminates the interference.)

More on the Low-Cost Wooden Model That Moves: Designing a Morphing Handcycle By Seeing It In Action

Alan Ball sent along an e-Drawings file of the 3D Solidworks model that he used to cut out the wooden pieces to make the 1/8 scale model of the most recent design of the Morphing Handcycle.  An overview of the project is at www.movewithfreedom.org. This technique of using CNC-routed wood parts is very significant, because it lets us understand a design in "real life" at very low cost.

Note that our next design is going to take some of the concepts in this model, but will go back to a more planar frame, which will have more of a "bike" look. We may use this style of design on a future morphing wheelchair.

Click here: http://www.edrawingsviewer.com/ to download the viewer for Mac or PC. You'll need it to see the files below

Below is another output of the Powerpoint file that shows animations using the wooden model. The previous version used a PDF output, but I worry that the PDF takes a long time to load. Below are JPEGs from that same file. Just click through the images to see the frame animate.

A Wood Model Reveals: How to Understand the Self-Adjusting Seat on the Morphing Handcycle (choose full screen, and set view mode to "slide")

(Set viewer to "SLIDE" mode shown on lower left so animations will work)

This Powerpoint presentation and animation uses Alan Ball's clever and low-cost 1/8 scale wooden model to let us see how the seat bottom and seat back magically change angles to correct for tilt when the bike morphs up and down. Very cool, and it really works! (Note: this is a re-post using a PDF format from the the original Powerpoint)

A Self-Adjusting Seat Mechanism for the Morphing Handcycle - Refining the Design (including a 3D Model)

This is an improved design from Alan Ball that uses the morphing struts to correct for seat tilt as you morph up and down.

Close-up of the seat adjustment mechansim showing the base supports for a slung seat design. The link arm shown in red causes the seat to adjust as the morphing happens.

The next step is to build a test rig to see how all of these designs work in real life before committing them to a finished design.

Here is the e-Drawings file for the SolidWorks model:  You'll need the free e-Drawings Viewer (for Mac or PC)

Designing a Seat for the Morphing Handcycle - A Look at How Other Recumbant Seats Are Designed

Document processing pending. — Download Move_With_Freedom_morphout_sea.ppt


Alan Ball, Rory McCarthy and Bill Warner had a design session on July 10th 2009 to review how other seats have been constructed, and how the MorphOut seat might be made.

We concluded that the Longbike seat, on page 7, was the applicable to our design, and that we should make contact with them. Perhaps we might just incorporate their seat design into the Morph. They have a nice sliding mechanism, and also an adjustable seat back angle.


A Morphing Seat For The Morphing Handcycle - How to Correct Seat Position When You've Tilted the Frame by 20 Degrees

Alan sent these screen images along with a cool shadow border, so our post gets a slightly different look.

Shown above in green is the proposed morphing seat. Actually, there is the boxy (just for layout...not the real design) seat sub-frame. The end of the morph arm, along with the little tab that moves (how?) adjusts the seat angle to be correct in both low rider and high rider positions.

Oblique view.

Side view in high rider. The 74 inch rider isn't there.

Mid morph. The seat morphing mechanism is beginning to tilt the seat backwards.

Now the seat is tilting back more to correct for the morphing down, and to move the rider to the correct low-rider tilted-back position.

All the way down, in low-rider mode.

Issues to think about: 
1. How do we support the seat back? Needs to be very rigid as you power the pedals. Looks like it would be hard to put a strut between the morphng frame and the seat back, because dimensions are changing
2. Need a foot rest that lets the rider rest their feet in both low-rider and high rider positions.

Here is the e-Drawings file for the SolidWorks model:  You'll need the free e-Drawings Viewer (for Mac or PC)

The best way to visualize the design is to use this 3D viewer and change the configuration pull down to move the bike through its morphing range.




A Self-Adjusting Seat: Alan Ball Presents Two Designs for the Next Morphing Handcycle

Rory, Alan and I had an online design review session today. The latest design from Alan Ball looks at two ways to make the seat self adjusting when you morph. This version puts a hinge below the seat, at the same joint as the front morphing joint. There is a knuckle attached to the seat back that forces the seat forward as you morph down.

Bobby Hall seat positions shown in blue. Note that the Morph in low rider is a longer vehicle than the Bobby Hall. And that the rider sits further forward. Our seat height is about the same.

Now in high rider mode. Notice that the knuckle behind the seat is shorter. This tilted the seat back in high rider.

This is a different approach. A subframe is hinged just below the front of the seat. A tab pushes up the rear of the seat as you morph down. The seat tilts up at 11.5 degrees, which is what you want.

Version 2 showing the seat inn high rider mode. The mechanism has lowered the rear of the seat, and reduced the tilt. The grey lines show what the tilt would be without the mechanism. That tilt would be uncomfortable at best.

We are 2.87 degrees tilted forward. This seems to work well in high rider mode.

Without a seat tilt correction, the tilt is almost 11 degrees forward, which is not acceptable.

Click on the two versions of the model below to see it in 3D. You'll need the free e-Drawings Viewer (for Mac or PC)