MWF Morphing Handcycle Project Blog

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Morphing Handcycle - Learning from the wooden model.pdf (9343 KB)

(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)

Rory, Alan and Bill met to discuss next steps for Move With Freedom and the Morphing Handcycle and the Morphing Wheelchair. Alan brought along an important breakthrough: A low cost 1/8th scale model of the latest handcycle design. This working (it morphs!) model was made using a CNC router, cutting out thin plywood. Alan's friend did it for $100! Wow, that is amazing, and so useful. This model shows a new version of the design that includes automatic adjustment of the seat bottom and the seat back.

I'm holding up the single sheet of plywood that supplied all the parts for the model. It's really amazing that a fully working, accurate scale model can be made so quickly, easily, and cheaply.

This is what we're calling "Morph 2.5" Morph 2 weighed almost 60 pounds, while Morph 3 was about 40. But Morph 2 worked better, and had better steering. At the recent MassTLC Innovation 2000 unConference, Rory wanted to come with an improved vehicle. I a period of just a week, George Reynolds and Rory combined Morph 2 and Morph 3. They took the aluminum front end from Morph 3, and fixed the footrest design, and put that on Morph 2. Then George removed the vestigial angle adjust mechanism that didn't work out on Morph 2. That also removed one morphing joint. Voila. We cut some 13 pounds from the weight! (Background has been hastily Photoshopped to remove clutter.)

Here's Morph II as stood during our marathon measuring session last summer. Notice that the struts are gone, one morphing joint is gone, the steel footrests are gone, the steel front end is gone.

The main tube is crumpling. Oops. Too much force, all piling up in one spot. We'll have to fix that. Rory was noticing that the pedals seemed to be getting closer to him as he rode.

Closeup. The tube had too much force on its surface. Can't do that!

The steel "test rig" set up with a bungee lift system. No gas springs. Also note the seat has the self-adjusting mechanism. so when you morph, the seat automatically corrects for added tilt. It works so well you don't know its there.

Note the big black shock cord bundle. It's helping me morph up.

Now I'm morphed down. Note the path of the cord. It goes between the two steel members. The bungee lift system works better with a clear center span, and with flanking support members. This frame design can also accommodate a single gas spring.

Alan Ball sent along this concept that is based on our recent design meeting at John Baron's shop. This design separates two morphing arms to make the rear frame more 3D, instead of the earlier designs that essentially have the frame all in one vertical plane. The idea is to get better torsional rigidity and reduce weight. This design is based on using an NEMSHPEC gravity reduction system. (NEMSHPEC stands for Nylon Encased Multi-Strand High-Performance Elastic Cord ... or to most consumers "bungee" cord.) Instead of the gas springs of our earlier designs, this vehicle will actually use a multistrand shock cord to provide the morphing lift. We've tested it, and it works great. Its also much easier to adjust than a gas spring, and it will be lighter and less expensive. I also belive it will be more reliable. At New England Handcycles, we used shock cord for seat components, and for the centering spring. The cords are waterproof, tough, and seemed not to care about sun exposure, even over long periods of time. (years)

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mbungee 2.EASM (483 KB)

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2009-07-17 Morphing Handcycle Test Rig MOV small.mp4 (24733 KB)

This post shows the uncut video from our design session at Baron Engineering on Monday, August 17, with John Baron and Alan Ball. Bill Warner mans the camera.
 
This video tips the scales at a Titanic length of 8 minutes, which in the "dog minutes" of the Internet translates to a major time committment (is that 56 "Internet" minutes?)
 
But there's a lot of interesting stuff here, including how you can make a morphing handcycle using bungee cords. (no kidding. Shock cord works great)

Here are all the photos from our August 17th meeting at John Baron's shop, with Alan Ball. Sorry, no time to do nice organizing.

 Here's what we were looking at:

 1. Can we replace the expensive, heavy gas spring with shock cord "spring".

 We tried this with a few bungee cords, and it worked rather well. See the videos in the next post. We will refine the approach this week by testing with shock cord set to balance John's weight. Note that without the gas spring in the way, flanking members on the frame work better, and the frame travel is much longer. The bike goes a little higher, but gets a lot shorter, and it can also go much lower, practically touching the ground if you let it. (we may have a removable stop for that)

 2. Could we get the damping and locking of the frame by using a standard bike brake hub?

 Again, we think the answer is yes. The internal drum hub would go on the joint under the seat and would allow firm locking of the morphing frame, at low weight, low cost. We think this control, along with some "end of travel" bumpers, may work well with the shock cord lift system.

 3. The seat bottom is from an office chair. Real seat won't be that big.

 4. The automatic seat adjusting system works like a charm. I didn't even realize it was happening. It just felt right.

 5. When you don't worry about weight, things really do get heavy. This test rig weighs about the same as a small refrigerator. (We knew that, but still interesting.)

 6. The adjustment mechanism for the gas spring didn't work the way we want. Turns out you have to adjust TWO attach points, not just one. This is because by changing only one point, you adjust travel AND pre-load at the same time, and they tend to cancel each other out. The shock cord lift system is actually much easier to adjust.

 7. As designed, the bike has a huge moment arm where the axle meets the morphing frame. If you ever hit one wheel and not the other, you'll twist the frame and it will be easy to make it go out of alignment.

 8. We discussed separating the rear flanking members to be closer to the wheel. This will triangulate the rear frame and will eliminate the moment arm. It will also let us use smaller tubes and save weight. Some of the sketches are related to this.

 9. John has a detailed spreadsheet that shows the calculations to maintain weightlessness at every angle of the frame, and for any rider weight.. (we should post it later)

 10. The pictures of Bill (in purple) on the test rig are meant to be a sequence, but they may be out of order in this post.

 11. Alan is going to make some very rough concepts for review next week when Rory returns.

 12. John is going to work on the shock cord lift system.

 13. The items we talked about could make the morph lighter, stronger, cheaper, more reliable, easier to adjust and easier to build.

                                                                             

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Photos_of_the_Morphing_Handcyc.zip (8987 KB)

     

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Morphing_Handcycle_Test_Rig_Pr.zip (1353 KB)

John Baron sent along these images of the morphing handcycle test rig progress. The goal of the test rig is to figure out how to get the best "float" so the bike goes down and comes up effortlessly.
 
Below is the gas spring we're using: http://www.mcmaster.com/#9416k51/=31aoi8

I took Lucas and a friend to Water Country in Portsmouth, NH (lots of fun) and on the way back, I stopped at John Baron's shop to see the new test frame in action.
 
While 3D CAD is amazing, it's hard to beat RL (real life)
 
This sequence shows the new morphing configuration in action. Alan Ball realized that in order to get the low riding mode we want, we should have a frame that has "dual flanking members." Which means that the part of the bike that goes up and down (the wheel to seat part) will fit in between two outer support members. This means that when the bike morphs down, it can go much lower because you eliminate the interference that stops the downward Morph in Morph II.. (Actually that was done on purpose in Morph II...so it would be rigid once you got down.)
 
Now, as you watch this sequence, you can see the benefits. The bike practically folds on itself in the up position (we probably can't do that once the gas spring is installed). And in the low position, you'll see that it can go REALLY LOW. (also not practical, but hey, fun to see.)
 
Note that right now we only plan to use the middle set of pictures as a real range. The very first ones and very last ones are outside the usable range of the full design with gas springs. (We think)

                     

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A_First_Look_at_the_Morph_Test.zip (3702 KB)

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John Baron with Test Rig-iPhone.m4v (10825 KB)

Here is a brief video showing John moving the test rig.

Note the automatic seat leveling device. Here in the low mode, it is tilting the seat forward. Note the angle between the left strut, and the small upper strut.

Now notice that the upper strut is almost parallel to the lower one. This tilts the seat back in the up mode, thus reducing the forward seat tilt that occurs with the morphing up.
 
Discussion: There is a lot of new ideas in this frame design. John has figured out a lot of details already in building the unit. He is also planning to use one gas shock rather than the two found on Morph II. This will save cost, and save weight.
 
In early discussion of the Morph, Rory talked about a "Super Tight" mode where you could make the bike even shorter than you might normally use, say for really tight spaces. This frame can do that, when going all the way up and when the morphing arms nest completely.

This picture shows the arm positions (roughly) in the high rider mode.

Now check this out. The twin flanking members are fully nested, and the bike will get a good 3" shorter.