Steerable sidecar wheel, and all its implications.

I have a week of exams, starting on Monday, and, as with "sidecar design formula", which was during and after my last set of exams, I am in full study avoidance mode.

So rather than thinking about marine engineering, I have been thinking about sidecars.

Consider this:
For a non-steering sidecar wheel, the "no scrubbing" position is level with the back wheel of the bike, where it will have little influence on tracking, due to no lead, regardless of how much toe in is applied, and will in fact have the opposite effect, as any toe in will cause the sidecar wheel to drag, and increase the imbalance of the outfit.

The greater the lead of the sidecar wheel, the greater the effect of toe in to tracking, so less toe in is required, but scrubbing is greatly increased at any turn radius.
The logical extreme of this is the sidecar wheel lead of half the bike wheel base, which greatly increases the outfits ability to turn away from the chair without lifting the back wheel of the bike.
Flying the chair would remain largly unchanged.

Now look at the whole system at the sidecar wheel lead of half the wheel base but with sidecar wheel steering included, by some form of mechanical linkage between the front suspension and the sidecar wheel, so as the steering is turned, the sidecar wheel turns to have the same turn centre.
There would be minimal scrubbing at both extremes of lock.
Toe in is still required, but due to the lead, much less than a fixed wheel outfit.

Another side affect of this would be very different handling of the outfit as it went over a single point bump, such as a speed hump, but carefull application of anti-roll bars, potentially from back AND front suspension over to the sidecar suspension, at the same time, would compensate for this, and greatly reduce roll at the same time.

The linkage from the steering would be strange, and require large amounts of thought, as the distance of the sidecar wheel to the turn centre in either direction is different, but nothing that can't (theoretically) be overcome.

So what are your thoughts on this

So, what YOU have in mind basically the EML GT Twin type -- but without its rearmost sidecar wheel?

This system is similar to the second axle on a dual steer truck. The second steering axle turns its wheels by a lesser angle determined by the ratio its set-back from the front, in regard to the overall effective wheelbase.

Then, you have to determine the Ackermann offset factor:
http://en.wikipedia.org/wiki/Ackermann_steering_geometry

addendum-

I've done thought exercises with mid-position outfit wheel placement some years back but the biggest problem is severe reaction to crossing obstacles such as speed humps. Unless active suspension was employed, driving into a supermarket carpark would leave the occupants either injured, or at least having to loose their lunch over the side!

But, if a mid-position outfit wheel design is contemplated, it would be a superior layout to employ front & rear wheel steering -- with the outfit wheel non steering.


Consider this wheel layout! Then remove the centre Left wheel, followed by both front & rear Right side wheels. After that move the C.O.G. left of centre.

The resulting 3-wheeler is steered by front & rear wheels. It can be driven by that same pair, or employ three-wheel drive. Front and rear wheels spin at same speed so a differential would be placed between their common drive and the (mid) Right-side wheel. With both-end steering in use, half the effective steering lock can be used since it would steer like a vehicle with a wheelbase half as long!

But, as I said at the beginning- active suspension would be a necessary inclusion.

I should have know that this idea had been visited before, and trust EML to have actually built it.
I wonder how it ran, if the speed bump problem killed it?

One problem I foresee with the second system, both bike wheels steering, is the speed of responce.
This is based on driving a JCB loadall, which had a number of steering options, front wheel only, front and back wheels counter steering, and crabbing (both front and back turning the same direction).
And driving at speed in both ends steering mode was "interesting".
But sidecars are quick steering to start with, so the rider would probably compensate eventually.

Thanks for your thoughts and insights.

I posted this in another sidecar thread a couple of years ago -" re Two Wheels article on the steering sidecar - found it after searching through a 5ft tall pile of TWs. The article was published in Sept 2000, the builders name is John Pizzey and there were two different outfits featured - the Honda CBR1000 with the steering chair and a Kawasaki KLX650 offroad unit.
TW should be able to provide reprints of the article if required."

The steering system used the roll of the outfit in turns to provide the steering input. Used a lot of rose-jointed links.

The Comanchee by Sidebike had a steerable sidecar wheel.
The Liberator by Dauntless (Formerly a European brand) had a steerable sidecar wheel.
There have been various homebuilts also with steering sidecar wheels.
Bill Ballou's design probably worked as good or better than any of them.
Harry Tarzian played with a steering sidecar wheel design on his 'Suba Guzzi ' but the rig never really ended up doing any milage to speak of.
Yes, with a steering sidecar wheel the benefit of running more wheel lead without the bad sides of doing that is the goal.
Steering sidecar wheel designs do have their own drawbacks though.
To try and get a real ackerman effect with a non symetrical vehicle such as a sidecar outfit is difficult in both directions.
To negate true bump steer under all possible conditions is difficult.
To have a design that will provide consitant feel to the operator under various conditions is difficult.
When riding with agression to the point of drifting in turns the correction by the driver for the drift at the bars can create a big issue when coming out of a turn dependant upon the load on the sidecar wheel at that time.
Heck go for it and see how it does for you Andy.

There is a complete difference between the EML GT Twin solution and other steerable sidecar wheels.

I'll leave the Dutch EML GT Twin for what it is. The concept or the idea behind it is different.

Sidebike France has (except for their Toro leaner) some kind of sidecar steering on all their outfits.

The mechanically sidecarwheel steering can be found on their Comanche, Comete, Mega Comete and Kyrnos.

The Renaissance has a hydraulic sidecarsteering.

The Zeus has extra steering on its rear wheel, becaus of its twowheeldrive.

I'v been riding most of these outfits.

It works, but you have to take into account, that the steering goes that easy, that oppossite to the "classic" outfits on fast curvy roads with the powerfull engines they use, you experience a oversteering effect in stead of the understeering effect, you guys have on your outfits.

Fun.

The more you open the throttle the more oversteering. Both in left and right curves. Especially the Zeus. All of these outfits don't have a steering damper. No problem, except for the Zeus. In my opinion it should have a steering damper, but only because it has a reverse gear. I experienced the bump steer effect only in reverse. The Renaissance nowadays has an option for the hydraulic sidecarwheelsteering. Some people don't like it. On fast rides (over 100 Mph) the feeling gets a littlebit "unstable", if you know what I mean. Must be the hydraulics.

Even (especially) the light-weight XJ 900 Diversion Kyrnos does great on roundabouts, but you have to watch the easy steering effect. Otherwise you stand opposite to the traffic.

Maintenance seems a littlebit tricky to me (because of all the extra linkages), but owners assure me that's not to bad. (but they do not ride on salty winter roads, like I do).

If you want an very easy steering outfit, Sidebike is youre choice.

Richard-NL

I realize that this is a 5 year old thread, but does the hand-drawn graphic below fairly represent the problem, given a hypothetical rig w/ a 60"wheel base, a 48" track, 24" of lead and 40 degrees of steering either way on the motorcycle?



I'd like to take a cut at putting together a steerable sidecar rig using my DL1000 as a tug but I want to be sure that I understand the problem before I start draining my bank account and frying my remaining brain cells.

Andy. Where you going for Marine Engineering?
I am an old Calhoon MEBA graduate.

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Lex, please tell more on how you engineer the steering of the sidecar wheel.

Basically, the project sounds interesting ~ but with the added weight and complexity . . . you may find that the overall benefits are marginal.

Conventional sidecar wheel plus a longer-than-average lead will give more scrubbing of the car's rubber, but that is a small price to pay [IMO].
If you are seeking more stability when turning (+/- braking) away from the car . . . then you might be able to achieve much of what you want, through designing a sidecar which allows judicious ballast placement.

Ballast can/should be easily removable, for certain occasions [such as visiting Tarka] and has the advantage of cheapness & simplicity.
Important of course, to have a design permitting the ballast to be rearwards & very wide & very, very low.
Not that I'm saying anything new there!

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Some good posts above....lots of variables some of which are positive and some negative . We are doing a rig now with a steering sidecar wheel to haul a wheelchair. Why? It will allow more wheel lead with minimal scrubbing . The rig will be driven from the wheel chair in the sidecar so we want more lead for stability and want to minimize scrubbing and excessive tire wear with the steering sidecar wheel. In most cases I think it is more trouble than it is worth but this is an exception.

I am considering a sidecar chassis w/ with a parallelogram trailing arm suspension similar to the old-style VW front suspension. The sidecar wheel's steering knuckle would have castor and king pin inclination like the VW's as well. I'm considering making it steer w/ bell cranks and Ackermann geometry, but the challenge appears to be retaining that geometry as the right wheel is shifted from the forward to the rearward position. That was what drove my original question.

I burned a few days and multiple brain cells until I finally settled on a configuration which uses an idler bell crank in place of a forward wheel and moves a steering arm, via a second idler bell crank, on the sidecar wheel's kingpin. I can see that I should have paid more attention in my geometry and trigonometry classes.

I'm probably at the point where I need to do a wooden mock-up so that I can move the pieces and parts in relation to one-another and document what happens.

Let us know how you make out when you begin figuring ackerman in both directions I think Bill Ballou worked it out pretty good on his old Wing powered outfit.

Also camber curves can make things interesting due to caster on the sidecar wheel.

And of course there is also the bump steer concerns which need to be addressed.

Some have just said the heck with it and designed things to allow some turning of the sidecar wheel (slight) and went away from the true ackerman idea. Benefits were still there I suppose but the complexity of steering a sidecar wheel is still of questionable value to many of us.

Oh...... for what it's worth.... food for thought and all that....One thing to be aware of is that once the outfit is done it will probably exhibit different results than expected if you ride aggressively. True drifting must be done with caution. If you are sideways in a turn with opposite lock applied ( power oversteer) the thing wil very likely correct itself vary very quickly when it does and can very likely send you in a direction you do not wish to go. Many of the French rally High Performance sidecars have turned away from sidecar wheel steering due to this. I have some picture of ralph G. here in the states where he left the road and went over a bank and was stopped from ending up in a creek because th sidecar went on one side of a tree and the bike on the other.... pretty graceful but could have been worse. This was a FJ Sidebike Comanchee. Bill? Roger? You guys reading this???

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Claude makes a good point about [minimal] designing for the "correct" Ackerman angulations.

The right Ackerman biz is obviously important in a heavy vehicle, where steering loads and high traction from large grippy tire contact-patches apply . . . and in mostly-urban usage, where tight turning circles are frequently made.

But for a lightweight recreational vehicle, with a skinny lightly-loaded sidecar wheel ~ I would hope that just a moderate approximation to "Ackerman" would suffice.
Important to get the "almost straight ahead" steering correct, and also to minimise bump steer.

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Just to throw something real crazy out there, has anyone ever tried a sidecar suspension set up like the front wheels on a shopping cart with some trail so the wheel follows where you turn. I'm a little scared to try it, what happens at high speed? Maybe you would need a steering damper to kill any wobbles. Backing up would be interesting too. The wheel would try to swing around to go the other way. Carl

It might work O.K. going forward. You'd have to devise a lock to keep it straight going backward.
Would there be any advantages to it. I.D.K.
I think I'd go with the Keep It Simple rule.

Yes.....The late Fioyd 'Pop' Dreyer experimented with a caster wheel sysem for a while and it worked okay. There are still quite a few Dreyer sidecars around here and there. Yes, it did okay but was terrible to back up lol. Greg Tennbrook still has one I believe.
He also did a lot with leaners years ago in the racing world. Google POP DREYER and you may get some interesting things to look over.
The book " They Called Him Pop' is a good read.

links to the article I referenced in post #5

https://www.advrider.com/advrider-photobucket-images/images/k/kiwi_accord_001.jpg

https://www.advrider.com/advrider-photobucket-images/images/k/kiwi_accord_002.jpg

https://www.advrider.com/advrider-photobucket-images/images/k/kiwi_accord_006.jpg

off-topic comment...

Many thanks for this:

I have only 3" lead, but a lot of toe-in for the sidecar wheel and now I know why the rear tire on the tug is getting the most wear by being pushed sideways! Today I plan to point all three wheels in the same direction (being certain the tug wheels are aligned) and then see what I need to keep my rig running straight before purchasing another new rear tire.

Again, thanks.

measure toe in using the sidecar wheel and the rear wheel of the bike only. Measure across just in front of the front wheel and just behind the rear wheel. Typically 1/2" to 3/4 toe in is a decent staring place. Reducing a little at a time may be beneficial as you watch tire wear patterns. Toe out will cause a pull toward the sidecar.
Three inches of lead is very small. Turns away from the sidecar may be dangerous if done with any aggression or speed unless you are running a hardtail bike or a very heavy bike with a very light heavily sprung sidecar.