Sidecar wheel steering etc.

[Jan from Finland]

My guess is that you can't justify the price of electric steering by better tire wear or less fuel consumption.
In search of improved dynamics it might be justifiable.

However, there are few fundamental differences between a land and marine vehicle's steering.

Marine environment
+ Insensitive for few degrees of actual steering error.
+ Relatively insensitive for short uncontrolled burst of movements
+ Slow speed actuators are fast enough to control steering

Land environment
- Sensitive for small steering errors
- Steering is used all the time, thousands times more often than in marine environment
- Steering corrections are small and require great precision and consistency
- Sensitive for short uncontrolled movements
- Steering rate (acceleration in degrees) is high

I wouldn't worry too much about Ackerman offset or amount of steering required because those can be calculated fairly easy. I would worry about reliability. My experience is that you can never have an electric steering system which is both cheap and reliable. Steering system of land vehicle has to be consistent. There is no room for error.

Using levers, pulleys and steering cables sounds more reliable... In a passive steering system there is less to go wrong.

Originally Posted by iantochips

A linear electric drive would have zero feedback and therefore no feedback to the steering over bumps. Same with hydraulics (suitably valved): I think the feedback you want is only steering feedback from the bike's steering- not what I think chassis designers call bump steer.

Bump steer means that your steering system reacts adversely to bumps. Suspension compression changes toe-in (or camber). That causes inconsistency in steering, especially while cornering, and may lead to oversteer (or understeer). The same is true for any active steering system (like linear actuators). If you can't be sure of the state of active system - you are in trouble. Lack of feedback wouldn't save you from bump steer.

[newellbc]

Some of the new ATV's are running electric power steering. And all the magazines praise it as a safety measure. Riding ATV's and hitting a log, can almost throw you off the ATV. With the electric power steering there is no kick back at the handle bars. So, I would look at some of these systems. Honda and Yamaha are both using it. I'm sure others as well. The one article I saw on the Honda, showed units that had most of the electronics built into the steering assembly. Blaine

[Billtr96sn]

Originally Posted by iantochips

Looking to build my first outfit after 30 years without. Got loads of ideas/possibilities.....!

Reading stuff here I see lots of references to sidecar wheel scrubbing and the compromise forced on wheel lead by the (understandable) desire not to dig the chair into the tarmac on the first bend. It does seem that a few degrees of steerability on the chair wheel would help considerably. It could be proportionally linked to the bike's steering using levers and the bulletproof steering cables used on powerboats, for example. Or electric- quite a few cars with electric power steering, and I think immediately of the neat, reliable and small (12v too) linear electric actuators on marine autopilots.

My thinking is that optimum lead could be used with this set-up. Less scrubbing, better tyre wear and less fuel consumption?

Am I barking up the wrong tree, or just barking?

Incidentally, I'm told that Harleys, maybe just old ones, can be set up with no lead at all. I'd love to know why?

All bikes can be set up with no lead, the 2wd Urals have no lead as well. I have flown against conventional wisdom with my outfit on some parts as well, but it works as a whole.

[iantochips]

Lots to think about! But an interesting discussion.

Jan, you're wrong about feedback in electric linear activators- they have to be driven in each direction, and have to hold their position when no input is made against very considerable loads. They also, in some cases, react very quickly although with limited stroke- their surplus power means this can be enhanced by a simple lever. In racing yachts they do respond fast, and make lots of very small adjustments very quickly in some situations.

We are talking I think as well about limited lock on the sidecar wheel- this is about reducing scrub and getting nearer to ideal geometry, not reaching the perfect Ackerman angle of a symmetrical four wheeler.

The twitch problem can be resolved by a deliberate 'dead zone' around dead ahead. This should deal with calming down small steering inputs.

Have to work now! But I'll be thinking about this in the bath later.....

[Jan from Finland]

Originally Posted by iantochips

Jan, you're wrong about feedback in electric linear activators- they have to be driven in each direction, and have to hold their position when no input is made against very considerable loads.

Sorry, but did I say something about feedback? If you are referring to bump steer, it has nothing to do with linear activators. It happens because of geometry of suspension, even with solid components.

My main point is that in a sidecar wheel even a difference of one degree in geometry, may lead to unexpected handling. Precision and reliability are the most demanding design parameters in your application.

Let us to know what you end up doing. It's always fascinating to see innovation in work.

[iantochips]

You're absolutely right Jan- I think I was confusing your point about geometry causing bump steer, with the issue of people disconnecting the steered sidecar wheel because it affected the main steering. The latter problem I assume was more likely to be caused by unwanted feedback?

It's interesting to think that all conventional outfits use constant geometry in the suspension- forks & swinging arms in various configurations, and have none of the advantages endowed, say, by useful camber change created by unequal length wishbones.

I'm waiting for someone to relate a really good experience of the system working, perhaps only let down by the system chosen to operate the steering rather than the principle itself.

[Salsa]

Semi leaners (the motorcycle leans but the car does not) have sidecar steering.

Check out the discussion.

Don

[sidebike]

Here is a few pictures

[vortexau]

One major disadvantage of excessive sidecar wheel lead (picture wheel at mid-wheelbase position) is the gross changes in lean LEFT-RIGHT-LEFT (or RIGHT-LEFT-RIGHT, depending on side of the road one drives on) such as driving over a series of Speed Bumps in a shopping area car park.

The effects of this on outfit rider & passenger is more extreme than on automobile driver & passenger/s due to the short, narrow wheelbase & high riding position.

Otherwise, the best engineered one piece design would be a front & rear steered longer outfit with mid-position non-steered outboard wheel!

[iantochips]

Rear wheel steering to think about now Vortexau?!

I guess the permutations are endless. I see from sidebike's pics that, in this design at least, a considerable amount of steer is allowed to the chair wheel- I'd been thinking more in terms of alleviating scrub than going for 'ideal' geometry. Like that front end though.

[B.E. Coyote]

My Uncle had a small part in helping to build this as he worked in Al's machine shop.

I have seen it and it is impressive. I don't know anything about how well it functioned.

http://www.bobsbmw.com/community/sidecarproject.html

[Jan from Finland]

No sure if you already have seen this but it gives you an idea in layman's terms what to expect when playing with toe-in and camber. http://advrider.com/forums/showpost....75&postcount=3

If I were designing a rig I would like to have suspension geometry which by changing toe-in and camber reduces pull to right while accelerating and reduces pull to left while braking. I wouldn't worry about scrubbing.

I am not sure if all conventional outfits use constant geometry in the suspension because unequal length wishbones are not the only way to achieve passive steering. For example Porsche 928 used Weissach axle. Many others (like French hot hatches, BMW and Subaru) have used semi trailing-arm or even twist-beam suspensions. I wouldn't be surprised if some of that is already build-in some designs.

Having a 2WS should give more options for the geometry. Although it makes the actual design process more complicated. Like you said, permutations are endless...

[iantochips]

That BMW K100 outfit is impressive- I note (I think) that it's not truly hub centre steering, as you'd obviously need on a solo, but the hub is offset like a car. Can't see any disadvantage and proprietary bits would be much easier to find.

Love to know who finished it and how it performed.

Jan, I thought of unequal length wishbones as the classic racing car set up, sometimes combined with a torsion bar 'spring', but as you say there are many others. There's something inherently pleasing about the simple wide based wishbone, and it's easy to fabricate, or pinch off something else!

No takers on my transverse rear engine two wheel drive idea? There's a rolled Smart Car in a scrapyard not far away....

[Jan from Finland]

Originally Posted by iantochips

No takers on my transverse rear engine two wheel drive idea? There's a rolled Smart Car in a scrapyard not far away....

Interesting, it could work. Rear engine in a hack is not a new idea.




Modern road racing sidecars are rear engined.



Smart's diesel engine is already used in this Dutch (prototype) motorcycle. Track T800CDI.



Just make sure it doesn't start to resemble something like this T-55 tank from the scrapyard.

[oppozit]

Or you could simply go with a proven design like the Jianling JH600BJ - over 13,000 units made. Probably the largest sidecar manufacturer in production and maker of the only military sidecar since the 1980's. Some English language Chinese websites give a full description of how the system works.