Chainring: 25 t
Drive Gear: 23 t
Front Low Ratio: 0.57 - yields an 11.5 gear inch low
Front High Ratio: 2.34 - yields a 46.8 gear inch high
100 RPM Speed: 13.9 mph
Overall Ratio: 4.09
Speeds: 11
Shifting: Shimano Di2 electric shifting
I asked Cody to write up an analysis of stability for the three different handcycles. Part of the goal of this blog is to provide some of the basic building blocks for others that might make new designs. Cody provides a detailed way of looking at stability for these three-wheeled vehicles.
Here is Cody’s analysis in a Word viewer. After this is a link to download the Word file.
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Gear | Gear inches |
Metre development |
Gain ratio |
Front/ rear |
60 rpm | 80 rpm | 100 rpm | 120 rpm | ||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
mph | km/h | mph | km/h | mph | km/h | mph | km/h | |||||
Very high | 125 | 10 | 9.4 | 53/11 | 22.3 | 36 | 29.7 | 47.8 | 37.1 | 59.7 | 44.5 | 72 |
High | 100 | 8 | 7.5 | 53/14 | 18 | 29 | 24 | 38.6 | 30 | 48.3 | 36 | 57.9 |
Medium | 70 | 5.6 | 5.2 | 53/19 or 39/14 | 12.5 | 20 | 16.6 | 26.7 | 21 | 33.6 | 25 | 40 |
Low | 40 | 3.2 | 3.0 | 34/23 | 7.2 | 11.6 | 9.6 | 15.4 | 11.9 | 19.2 | 14.3 | 23 |
Very low | 20 | 1.6 | 1.5 | 32/42 | 3.5 | 5.6 | 4.7 | 7.6 | 5.9 | 9.5 | 7.1 | 11.4 |
Chainring | Int Small | Int Big | Int Drive | Front Small | Front Big | Full Low Gear In | Full High Gear In | |
New England Handcycle | 25 | 13 | 38 | 28 | 13 | 38 | 9.7 | 82.8 |
Travel Bike | 25 | 0 | 0 | 0 | 0 | 0 | 9.7 | 25.3 |
Electric Bike | 26 | 11 | 36 | 24 | 11 | 42 | 8.3 | 103.1 |
Drive Gear: 24 t (mounted to mid drive)
Low Gear: 42 t (24/42 * 20 = 11.4 gear inches)
High Gear: 11 t (24/11 * 20 = 43.6 gear inches)
Low Ratio: 0.57
High Ratio: 2.18
I can’t imagine mounting this big motor up by the pedals.
Hmmmm… Maybe Jim Turner himself will provide some expert guidance. Stay tuned.Question 1: How big a deal is it to give the motor a 11.4” (virtual) front wheel vs a 20” front wheel for Bionx?Question 2: How big a deal is it to give the motor an equivalent 43” front wheel for speed, vs a fixed 20” wheel?
ORIGINAL: 11, 13, 15, 17, 19, 21, 24, 28, 32, 36T
MODIFIED: 11, 13, 15, 17, 21, 28, 32, 36T, 24T
(bold sprockets are one unit)
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Hey Bill,I was able to spend a little time today on the handcycle.Anyway, I set out to start to get the geometry of the electric handcycle to start to make sense and see how everything fits together and relates. I started with the travel bike and started with adjusting the geometry for a 20" wheel. I decided to keep the following constant:- Head tube angle (55 degrees)- Amount of trail (.981 inches)- Wheelbase (50.375 inches)- The position of the pedals in relation to the position of the seat- Seat height off of the groundEverything else was up for adjustment.
I found that as I moved the front axle up (necessitated by the larger front wheel) the pedals moved forward. So, the seat moves forward as well to maintain the same relationship. This has the added benefit of putting more weight over the front wheels which should help with traction.To maintain the same amount of trail, the headtube/steerer offset changes to a little under 5 inches.
You will also notice a little L-shape near the bottom, these are the footrests. Since we didn't take this geometry from the travel bike, I took it from the NEH. I think it will be important to have that in the model to determine how to place the miter in the main tube.Moving forward a little bit I roughed in some tubes, using the same diameters as the travel bike.
I found that the miter in the main tube is probably going to be a requirement. Since the increased front tire diameter would otherwise increase the height of the main tube by almost two inches, it would be very difficult to get your leg over the main tube if it were not mitered. I just kept the main tube horizontal in this version which works well aesthetically I think.
If we were to use a continuous main tube, rather than a mitered one, this is what it would look like.I would imagine this gives it more of a rakish look than you were going for.
I also know you didn't want a bent main tube for aesthetic reasons, but it was easy enough to model it, so I made a quick version like that
Probably difficult to get a good idea at this point but as we get more detail in there with wheels, crank, etc. we can play with these things some more.Next up, I'll be going to the shop tomorrow so I can get some good fork dimensions and start to design the whole pedal/steerer assembly in a bit more detail.Let me know what you think so far.Cody
We're still at an early stage of the design for the Electric Handcycle. Many design choices depend on the components being used. So I started a database of components being used, and how these components fit together into assemblies. The fabricated components will eventually get drawings, and these will be accessible in the database as well.
Click here to see the live status of the Parts table in the database. It will open in a new window. Note that these parts are only an intial cut at selections. Ted and Cody and I are going to take a new pass through the components soon.
Note that you can click around the database all you want, but even if presented with a button like "Add Part" it won't let you. It might say to ask for permission, but we have to restrict editing of the database to those on the team. So view all you want, but please leave any editing buttons as they are (strangely, Quickbase doesn't let us take away all the buttons that Web viewers should avoid.)
This a screenshot of the Assemblies table in the database. Again, as of this post, these are preliminary. But if you click on this link much later than this post, the state of the database might be more reflecting of the actual plan (or even the reality.)
And here is the Vendors table from the database.
This post will review an initial Sketchup model for the Electric Handcycle. It is based on measurements made at our kickoff meeting. Mostly, we'll use the design parameters of the Travel Bike, but with a 20" instead of a 16" wheel.
This model was made using my instructions by:
Note that the real design is being done by Cody Wojcik using Solidworks. This model is for visualizing the machine. It's reasonably accurate, but not at all suitable for dimensioning parts like the Solidworks model will be. Still, it is efficient, because Geoff made the model in 90 minutes based on my instructions over a Skype screen share. I had previously searched for lots of bike components, so we were ready to move quickly.Geoff Bostwick
Overall length: 72"Front wheel: 20"Head tube angle: 55 degreesPedal height: 39 inchesPedal tube offset from head tube: 4 inchesRear track between tire centers: 24.5 inches
An earlier post showed the gearing range of the NEH vs Travel Bike. The NEH has a much wider gear range due to an intermediate derailleur. The Electric Handcycle will also have an intermediate derailleur. We're hoping to use a 9 to 44 tooth derailleur used on mountain bikes that use a single chainring.
Click the link below to download the Sketchup Model. It was made using Sketchup 2015.
This yields a full high gear of 106, and a low gear of 7.8 gear inches. This low gear is lower than both existing bikes, and the high gear is higher. But this is done in large part by using a pretty extreme 9-44 cassette at the intermediate drive. We’ll see if that really works out.Upper Chainring: 25tIntermediate derailleur small cog: 9tIntermediate derailleur large cog: 44tIntermediate drive: 24tFront derailleur small: 13tFront derailleur large: 36t
TED WOJCIK CUSTOM BICYCLES
4 Wilder Dr.
Unit 10D
Plaistow, NH 03865
phone: 603-479-3799 - Monday-Friday - 9am-5pm EST.
email: tedwojcik1@comcast.net - anytime!
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The previous posts review the Travel Bike, because it shares many design elements with the Morph. Having just spent the weekend in Newport on the Travel Bike (as I wait for the Morph 4 to be completed!), I wondered if we could use the very cool hinged footrests from the Travel Bike. The short answer: No. The Travel Bike, as compact as it is, is way longer than the Morph in high rider mode. And your legs sit well ahead of the steerer tube, as opposed to behind the steerer tube in the Travel Bike. Too bad. The Travel Bike's footrests are light and functional. Here's some more details.
Side view of the Travel Bike.
I used Keynote's instant alpha feature to grab the CAD Man from the Morph pictures. I scaled both drawing so the front wheel was the same size.
Using the same scaling techniques to see the Morph in Low Rider next to the travel bike. Note that you sit about one full head height lower. The overall length is about the same.
Adding the Morph in high rider, we see how much shorter and higher the bike is, even compared with the (mostly grayed out) Travel bike.
It's interesting to note how much more your leg bends from low rider to high rider. This is because the seat moves up and forward, but the footrest stays in a similar place (it does rotate about the front contact point, I think.)
Like I said, no but you'll see.
The instant alpha took away some of the foot of our CAD Man.
These footrests are hinged at the top of the vertical orange line, and also where the two lines meet. Go off a big curb? The footrest just bends forward, no problem.
Red lines show center line of your shin in both bikes.
I hadn't realized that the seating position relative to the steering axis was that much different. It's a good 16" (size of the front wheel). This keeps the Morph short, which is really crucial for indoor maneuverability.
And there you have it.
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Since the Morph will use some of the design concepts of my Travel Bike, here is a photo survey showing how the bike comes apart. It gets very small, and will fit in most trunks, and can go on small airplanes as well. The Morph will use the same coupler on the main frame, and it will have a similar fold-down seat. The Morph will put the centering spring entirely on the front, so the step of unhooking the centering spring will not be required.
Click on the small right arrow to view successive images below. This will give you a photo animation of how the Travel Bike comes apart:
Click on the small right arrow to view successive images above. This will give you a photo animation of how the Travel Bike comes apart.
Below is a photo survey showing more detail about the Travel Bike. It has a coaster brake in the hub, so the cam-based reversing brake isn't needed. The internal-gear hub has 8 speeds, which is okay for basic needs. The Morph has a full derailleur system, which will give it much more gear range.
Travel Bike photo survey.
Here's a picture of me on the Travel Bike. These photos were taken on a trip to Atlantis in the Bahamas. Thanks to Miles D. for demonstrating the disassembly of the handcycle.
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This post will go over the centering spring design we'll be using on the Morph. This design has been used on the New England Handcycle for over 30 years with great success, and it was carried over to the Travel Bike (shown below) that was built for me by One-Off Titanium (Mike Augspurger). The Travel bike and the Morph share many design elements, including the 16" front wheel, the coupler to allow breaking the main frame into
Here is the centering spring as installed on my Travel Bike. Note the silver coupler in the main tube. Because the bike comes apart here, there two carabeners below allow the centering spring to be dismantled when the bike is taken apart.
Closeup of the centering spring. I can't say it's pretty, but it works perfectly, as the explanations below will outline. This same mechanism will be incorporated on the Morph, but on the front end, rather than under the main tube. And, we'll make it look much nicer.
This series of three photos shows how one chain becomes slack and the other stays tight when the rider starts turning the wheel.
This is a bottom view (well, the bike is flipped vertically) showing the size of the wings.
When the wheel is turned, the wings pull on one chain, thereby stretching the elastic.
As the wheel is turned, the moment starts decreasing, while the stretch on the elastic, (I call it the "gap"), increases. The lines in red on the left side show the relative sizes of the moment and the gap.
As you start to turn more sharply, moment starts to fall quickly, even though the elastic is still being stretched more. This creates exactly the characteristic you want: Good centering near center, and up to about 45 degrees, and then a reduction in centering as you turn even more. Because the handcycle can make extremely tight turns, even more than 90 degrees, its important the the centering spring not fight you when you're doing these tight maneuvers.
At 100 degrees, we see that that gap is big, but the moment has dropped to almost zero. Just perfect. You can steer as extremely as you want, but lets say you need to grab the rear wheels and push like a wheelchair -- the centering spring will make sure the wheel stays straight.
Below are the five slides in a picture viewer, so you can click through them without the explanations above.
Here is the Powerpoint in case you'd like to play with it.
The Morph will implement the same mechanism, but the wings will be fixed to the main tube, and the elastic will be on the front end.
One of the design issues we've been working is how to get the seat back in high rider mode to tilt back enough.