Adding crazy tilt assembly... but to which frame?

[tiltmaniac]

Firstly, I'm posting in the Silvio forum because I'm thinking about <wincing> purchasing and then drilling</wincing> into a Silvio frame for this mod.


I've designed a tilt assembly based on a swing-arm design. Why? Because I'm very out of shape and I'd like some help balancing when going up hills... and so the tilt assembly is designed to give some balancing (i.e. self-centering) aid near in the middle ~15 degrees of tilt.


For now, I've been assuming that I should use a Silvio, mainly because drilling holes into the bottom flat plate seems like a "reasonable" thing to do when I'm bolting on additional material to help reinforce it.
.. I know, it sounds a hair crazy to me too, but what a project!

Here is the basic idea:
The rear (20") wheels would be ~18" apart, and leave the bike with roughly the same wheelbase length and angle.
Each of the wheels is mounted to a swing-arm which is 16" long.
This allows for a maximum tilt of ~52 degrees before there is worry about one of the wheels impinging on personal space, and ensures that neither swing-arm is close to 90-degrees and thus going to lock into position.

The swing-arms are connected with pushrods (in a pull configuration) to a cam which is mounted such that it slides along the "roll" axis of the bike. The cam is shaped such that the distance from its surface to the cam's pivot (which, remember, slides along the "roll" axis) varies as the tilt angle changes. This allows you to make the bike "raise" or "lower" itself depending on the tilt. To "lower" the bike, lessen the distance from the cam's pivot to the cam's surface at that angle. To achieve some measure of balance aid, "lower" the bike near 0 tilt. The weight of the bike and rider pull the sliding cam into an unmoving roller.

I'm happy to upload pictures of the kinematic model tomorrow if I don't get a plethora of "are you crazy" responses.

Fair warning: while the solidworks model is good enough to play with the kinematics of the mechanism, it isn't what I'd call a finished product: I still need to figure out exactly which parts to use for the swing-arm mounts (bushings vs ?bearings) and the sliding cam (sleeve bearing on rail, or can I just use another piece of tubing with some PTFE bushings). I'm not sure that will happen before the holidays, honestly.

So, crazy?
.. and if so, is it in a good way?

 

[mzweili]

Can't wait

Can't wait to see your design.

 

[Charles.Plager]

Of course it's a crazy idea.

Of course it's a crazy idea. So is building a MBB bike like the Cruzbike.

I'd personally start with a Sofrider or a Quest or even a conversion kit. Once you've got it working, then moving up the food chain makes sense.

So start postin' pictures!

 

[ratz]

Cut into a FRAME?  Drill

Cut into a FRAME? Drill holes? OMG who'd do that. *cough* Really it's all Buddies fault.


A good place to start might be to find a used Quest/Softrider; depending on what you are planning; the kick stand plate bracket is a great place to attach stuff. Any that can be attached there and successfully executed could then be done more exotically on the flat bottom of the Silvio. BTW with the way the bottom of the Silvio is constructed you could probably make an exterior clamp that was more effective than drilling.

 

[1happyreader]

buzzkiller

Tiltmaniac,
sorry to step on your engineering muse,
Google "adult training wheels"

As a potential friend and cruzbike rider I would ask say:

buy a used sofrider and install a triple crank with a granny gear.

Have the patience to do a thorough job , including low speed maneuvers, in the parking lot.

with experience, a low gear, and a sustainable cadence I bet you can climb your hills.

 

[tiltmaniac]

pics and comments

@OneHappyReader: haha

I've ridden both the Sofrider and the Quest, and my preference is for the Silvio or Vendetta, just based on handling.
I "get" the Slivio/Vendetta far more intuitively than the Sofrider or Quest.
I assume I'll want to ride it in the regular bicycle configuration, as Jon intended it when not attempting to do lots of climbing!

In all seriousness, I'd use a normal trike if I didn't love really having fun on descents and/or want to use it as a 2-wheeler.

The idea is just to make balance easier while going uphill (to put this into perspective, I'm looking forward to doing another tour-of-the-Alps where I'll be climbing for something like 8 hours a day for 3 weeks) without having to worry about flipping over on the descent, which can be otherwise exhilarating.

On low gearing: That isn't the issue. The issue is staying upright while crawling along at 2 mph on a 15% grade!

@Ratz:
?I have considered a clamp. We'll see!

images follow:

The image gallery for these pics can be found here: http://imgur.com/a/zdnjW

a:
Looking parallel to the ground at the bike while it is completely upright.
If you look closely you can see that the cam (viewed edge-on here) is mounted on a sliding bit (which would be implemented using rails and a slider, in all likelihood).

b:
Looking parallel to the ground at the bike while it tilts at 45-degrees.

c:
closeup of the cam/slider assembly on the bike while the bike is tilting at 45-degrees.
Note that some reconfiguration of the geometry would cause the cam to rotate more in response to tilt.
I haven't bothered to do that yet.

d:
Looking from beneath the bike. The interesting bit here is the shape of the cam.

e:
Looking sideways at the bike with a 50-degree tilt and 20" rear wheels.

f:
Looking sideways at the bike at a 50-degree tilt with 700c rear wheels.

g:
Looking sideways at the bike at a 50-degree tilt with 26" rear wheels.

 

[Charles.Plager]

That's more or less what I

That's more or less what I expected.

I think a Sofrider or a conversion would be the way to go as you could swap out the rear swingarm and add your tilting one.

There have been (almost) commercial versions that is somewhat similar. I thought they would be a good fit to a Cruzbike as well (I offered to use my Sofrider as a test, but somehow it didn't pan out... ).

 

[tiltmaniac]

Almost the same, but different.

@Doctor What:
I considered getting one of those for parts

Ultimately, all that provides is tilting, however, and none of the self-stabilization/balance assist stuff that I want.
Plus that one is a standard parallelogram tilter, and that suffers from some problems if you want to do any balance assist stuff, e.g. any change of height requires another hinge for the entire mechanism, or you end up placing lots of lateral stresses on the wheels that can be avoided with a swing-arm design, the parallelogram approach denies you the use of the rear of the bike for cargo, since the wheels tilt into that space, and lastly, the parallelogram approach denies you the ability to do three-wheel drive. Not that I intend to do three-wheel drive, mind you

This thing (in the pictures above) is a bit different than anything else I've seen thanks to the cam-on-slider thing allowing the whole assembly to be "programmed" in terms of the biasing of the height of the rear depending on the tilt-angle.

 

[Charles.Plager]

I agree with similar but

I agree with similar but different. But stop wasting time here, get a Sofrider or conversion and build this puppy!

 

[tiltmaniac]

Definitely working on it...

Oh, I'm definitely working on building it, though, given I get about 2 and a half hours a day of leisure time, it'll take a few months at least. :/

 

[Charles.Plager]

Just keep us (and BROL) up to

Just keep us (and BROL) up to date.

 

[baov]

Wow. That looks really

Wow. That looks really cool.
I don't have the spare change to do that to a Silvio but who are we to stop you!

 

[Shakey]

A couple of examples

If you had a way to lock out the tilt on the fly, you'd be able to be stable when needed.
If the lock was variable, you could adjust for camber in the road.
Something like a disc brake, the caliper on the frame & the rotor on the tilting part.
Just a thought.

https://www.youtube.com/watch?v=YAWgttpiqpc

-------------------------
https://www.youtube.com/watch?v=3JSTqIOORgI

Arrrgh! The embed video feature does not seem to work!
Just putting in the links ~!

 

[tiltmaniac]

I'm fairly afraid of doing a

I'm fairly afraid of doing a tilt lock-- I don't want to crash going downhill if it accidentally engaged. As a result, I decided that instead of going for 100% regular trike-like stability, is instead just give balance assist. Given the height above ground (desirable when biking amongst cars in my commute as it makes my wife worry less), I don't believe I could get regular trike like stability anyway.

We'll see if that works once it is built. Adding a tilt lock wouldn't be too difficult if that became the right thing to do. I hope it doesn't come to that, though! You're right that the nice thing about the tilt lock is that it can deal with road camber (and parking).

 

[snilard]

tiltmaniac: Why don't you

tiltmaniac: Why don't you simply buy recumbent trike?

 

[Kim Tolhurst]

one day,

the skittles will line up and a trike with a MBB will go, as we say in Australia, 'like stink'.

and, will be used in UCI competition. BE encouraged, and if I am wrong be sure to let me know.

Merry Christmas,

Kim.

 

[tiltmaniac]

snilard:
The main problem

snilard:

The main problem with a trike is that I tend to go quite fast downhill, and I'm fairly sure that I'd cause a trike to do an endo at speed.
.. which wouldn't be pretty.

 

[Charles.Plager]

tiltmaniac: Why don't you

tiltmaniac: Why don't you simply buy recumbent trike?

I see a more efficient drive train and better corner handling with a FWD tilting trike (assuming one could get all of the kinks out).

 

[tiltmaniac]

Have a Silvio S30 on order

Have a Silvio S30 on order for the project now.

Exciting and scary.

 

[Andrew 1973]

Build a test mule?

The most complicated part of the Silvio is it's front end. It seems to me you could fabricate a "main frame" test mule out of wood to which you could affix the front end and your tilting components before committing to altering the Silvio frame.

Just a thought.