[RIPPERTON]

Looks cool but with a rake like that I wonder what its going to steer like, hope not like easy rider Harley.

 

[Bruce_Kenobi]

Looks cool but with a rake like that I wonder what its going to steer like, hope not like easy rider Harley.

Thank you for your interest RIPPERTON, but I'm thinking the rake and steering in general will be....different, more on that soon!!

Here is a diagram of the bike as designed by Akira Creator Katsuhiro Otomo, I have compiled an image with the orthographic of the bike.

if you notice in the top picture of the side view of the bike there is a black thick line in front of the front wheel, that is reference and is on purpose there, it is a reference of the length of the rider's leg so since that is a part that can be measured, I took it out as a reference to get the measurements of the rest of the bike, with that I will get a clear picture of the size of the bike, as well as wheel sizes, the tires seem HUGE, let's see if that can be achieved or there has to be some compromise.

 

[Duncan]

Hi
With that layout a bike type of telescopic forks and simple steering won't cut it

You will need something more like a car steering system - still with the handlebars
Look up "Hub centered steering" or "Quasar"

If you use a decent type of front suspension and steering that type of bike has a lot of advantages over the normal head first system

 

[Bruce_Kenobi]

Hi
With that layout a bike type of telescopic forks and simple steering won't cut it

You will need something more like a car steering system - still with the handlebars
Look up "Hub centered steering" or "Quasar"

If you use a decent type of front suspension and steering that type of bike has a lot of advantages over the normal head first system

Thank you for your interest Duncan! you are right, I wasn't thinking on regular forks and simple steering, partly because of what you say, and partly because I have my sights on something completely different. The Hub centered steering has always been a fascination for me, but strikes me as extremely complex for implementation without professional equipment, hence I'm exploring something new. A lot of advantages? interesting! care to elaborate?

I have taken the reference I talked about my last post and came up with some measurements, but first, something important for this post: 1 inch = 2.54 centimeters (cm), 1 cm = 0.393 inches, now, about those measurements:

front tire: 83 cm
rear tire: 93.3 cm
lowest clearance: 8.3 cm
chassis length: 151 cm
Seat height: 45 cm
overall length: 341.6 cm
wheelbase: 253.3 cm
height from ground: 120 cm
chassis height: 106.6 cm
dashboard height: 8666.6 cm
headrest height: 106.5
headrest size: 20 cm
chassis width: 60 cm

With this now I'll start cross-checking with actual tire sizes.

 

[Duncan]

Hi Bruce
Look forwards to seeing what you come up with although hub center steering is really not very complex

One thing - contrary to popular belief a lower center of mass in a bike makes it more difficult to balance - not less

To illustrate that point take a 12 inch ruler and balance it on end on your hand then repeat for a 3ft ruler - the longer ruler is much easier to balance

 

[Bruce_Kenobi]

Hi Bruce
Look forwards to seeing what you come up with although hub center steering is really not very complex

One thing - contrary to popular belief a lower center of mass in a bike makes it more difficult to balance - not less

To illustrate that point take a 12 inch ruler and balance it on end on your hand then repeat for a 3ft ruler - the longer ruler is much easier to balance

Thank you Duncan. You think? maybe I'm seeing a mountain where there isn't, do you know where I could find building information?

You refer to the inverted pendulum effect, you believe this bike falls on that principle?

ok, so I started going from the tires onward, so tires that are 83 cm and 93.3 cm tall. have to be constrasted with real tire sizes, usually tires have sizes like this:

110/90-21, which means:
110 milimeters width
90% of the width as height of the tire
RIM diameter 21 in inches.

This all comes down to a front tire with this size: 110/90-25, but RIM 25 is not standard size for tires, I doubt they even make those. For the rear tire is even more extreme! 93.3 cm means that using conventional rear tire designations and sizes you would have 130/90-31! a whooping RIM size 31!! I haven't found those sizes anywhere. If we think this through, it's starting to look like the original art for the bike:

can't be exactly done, look at how that lineart differs from the version made by Masashi Teshima, specially size and position of the rider, and size of the rider related to the bike:

what do you think? seems like the bike will have to change it's form in some way

 

[ken wont]

A couple of points to consider:

Recumbent bikes are very difficult to balance at low speed! ( a trike is much better) Although a bike this futurist looking probably has a gyro-stabilizer.

It's your bike...You can use any size tires you want! I did.

 

[Bruce_Kenobi]

A couple of points to consider:

Recumbent bikes are very difficult to balance at low speed! ( a trike is much better) Although a bike this futurist looking probably has a gyro-stabilizer.

It's your bike...You can use any size tires you want! I did.

thank you for your help Ken!

I have thought about a Gyro stabilizer, like the one Lit Motors proposes for their C1.

I see you have a very large tire in the back of your trike, where is that from? where did you get it?

 

[Duncan]

Hi Bruce
More difficult to balance does not mean impossible
Just don't expect it to be easier!
I have ridden a recumbent two wheeler of a few thousand miles - it's great fun!

Hub center steering
You need a front swinging arm - with suspension - that curls out to allow the wheel to steer then curls back into the center of the wheel
Actually much easier than making your own telescopic shock system would be and you lose most of the sliding friction problems

Car bits will be too heavy for this but racing rose-joints would be ideal
The only "secret" is to have the steering axis (the line the wheel turns around) on the center-line of the rim

 

[Bruce_Kenobi]

Hi Bruce
More difficult to balance does not mean impossible
Just don't expect it to be easier!
I have ridden a recumbent two wheeler of a few thousand miles - it's great fun!

Hub center steering
You need a front swinging arm - with suspension - that curls out to allow the wheel to steer then curls back into the center of the wheel
Actually much easier than making your own telescopic shock system would be and you lose most of the sliding friction problems

Car bits will be too heavy for this but racing rose-joints would be ideal
The only "secret" is to have the steering axis (the line the wheel turns around) on the center-line of the rim

Hi Duncan, thank you for the quick response.I expect the Mark 2 to be unlike any motorcycle riding experience so far, never ridden a recumbent so I'm hot on that trail.

Hub center:
The steering system I had in mind does have a front swing arm with a shock, but it is more akin to the one on the Travertson V-Rex. Have you seen it?

Car parts won't do, it would have to be something custom.

 

[Duncan]

Hi Bruce
That looks like the whole thing steers
I predict that it will feel bloody awful! - OK to look at but not usable on the road

You need to look at the tire contact point - and the point on the road that the tire rotates around

Optimally the two are quite close together with the rotation point just a wee bit in front of the tire contact point

 

[Bruce_Kenobi]

Hi Bruce
That looks like the whole thing steers
I predict that it will feel bloody awful! - OK to look at but not usable on the road

You need to look at the tire contact point - and the point on the road that the tire rotates around

Optimally the two are quite close together with the rotation point just a wee bit in front of the tire contact point

Hi Duncan, the steering mechanism moves the tire on a pivot point, and also the swingarm and it is connected to the chassis byt 1 point of rotation, it's actually quite smooth to ride. Check the videos on the Travertson V-Rex, they are cool.

 

[Bruce_Kenobi]

update! so, after finding out that tires WILL have to change, and that hence the shape of the bike will be slightly altered I came to the conclusion that I need to visualize the chassis in 3 dimensions and see how the length of the chassis and all the components will fit together, so I took a page out of the movie-vehicle-production-process-book and decided to go for a maquette to see how it will work, here are some pictures of that:

stay tuned!

 

[Bruce_Kenobi]

the maquette is almost finished, I thought I would post some pictures of it:

 

[Bruce_Kenobi]

ok, so after more research and analysis I've come to settle on RIM 21 tires, which of course are much smaller than the original drawing by Katsuhiro Otomo, but it will be far easier to build and service than going with any other exotic solution for the tire size problem. Having the maquette has helped a lot, here you see re-sized tires to fit the RIM 21 ones to the scale of the tire:

The rear swing arm is not made yet, only the front one, "front swing arm" you say? well yes, that is another modification I'm introducing and I already talked about some updates ago, it won't affect the final look, but there are some interesting points to be made. More soon!

 

[Bruce_Kenobi]

The maquette is coming up nicely, here another picture:

You can see I have put the newly sized RIM 21 tires as white disks at the ends of the scale model to see how this flare's up and compares with Otomo's vision, needless to say, there will be an impact, no HUGE tires anymore, however I still think it won't look bad either, I cooked up a photoshop pre-render of how the bike will look, taking the original art by Christian Pearce and making some adjustments to it, to see how far off will the bike be when done:

As always, comments are welcome.

 

[piotrsko]

2 comments: I would have liked to see the original wheel profile in the drawing to compare to the photoshop picture.

Are you aware of the tricycle effect lately in Harley wide glides with what looks to be about a 26 rim and 3.5 tire and wheel combo? Since it is harley, should be good for front or rear and it looks to be about 31" diameter.

 

[Bruce_Kenobi]

2 comments: I would have liked to see the original wheel profile in the drawing to compare to the photoshop picture.

Are you aware of the tricycle effect lately in Harley wide glides with what looks to be about a 26 rim and 3.5 tire and wheel combo? Since it is harley, should be good for front or rear and it looks to be about 31" diameter.

Hi Piotrsko! thank you for your interest

When you say "the original wheel profile" you mean the drawing? (it's on the other pages before) or the new RIM-21 size wheel adjusted over the model? (it's on the preceding picture, the 2 white discs over the drawing) or the real life wheel? (no pictures yet )

No, I was not aware of the tricycle effect you mention, a 26 RIM? nope! can you point me to some link? 31" diameter is much better than what I have. However Harley Dealers in my area are close to none-existent and it would require bring them from the US, still, your point is interesting, as I said: do you have any links?

 

[piotrsko]

Google 26" Harley 3.5 rim. J&P or a couple other motorcycle houses show up. C&p for tires. Might even have one or 2 made in china.

I wanted to see the difference the smaller wheels made to the original concept tire size, everything else looked correct. Now it kinda appears moped instead of MOTORCYCLE sized.