Side stick steering diagram,as installed in my trike.

[tinhorn]

Thanks for making that info available. You've saved folks a lot of time. I think I'm going to adapt a steering wheel to my first project--they're so carish.

[Liteway]

I posted this some time ago but then pulled it because I worried someone might try to use it, execute it poorly or rescale it to a different track, wheelbase, scrub radius etc. and demand explanation for why it didn't work.
So look at it as a curiosity, Don't build it.

There is a lot of wierdness here, as it does not conform to conventional steering geometry, mainly because there is no fixed steering box. For instance, the steering arms are directly behind the kingpin axes. That should set mister Ackerman spinning in his grave. Or maybe just laughing.

I attempted to overlay the straight ahead steering diagram with the full lock diagram so that the change in positions of the various components could be clearly seen as full lock is applied.

Apologies to the real engineers here for this amateur rendering.



Edit 9/30/16
I later learned;
4 degree difference in angle between the front wheels is not sufficient for my trikes track and wheelbase and resulted in excessive tire scrub and understeer when cornering on a tight radius and steering that wanted to hold maxlock instead of self centering at the limits of lock as is normally the case. Steering arms should have angled in a bit in relation to the kingpin axes to make that difference 6 to 8 degrees.

I am making that changes as I convert from a ATV to CanAm Spyder based front end.
You will need to do your own diagramming and/or experimenting to find out what is optimal in your application.

[2rike]

Feb 6, 2016 16:14:28 GMT -5 Liteway said:

I posted this some time ago but then pulled it because I worried someone might try to use it, execute it poorly or rescale it to a different track, wheelbase, scrub radius etc. and demand explanation for why it didn't work.
So look at it as a curiosity, Don't build it.

There is a lot of wierdness here, as it does not conform to conventional steering geometry, mainly because there is no fixed steering box. For instance, the steering arms are directly behind the kingpin axes. That should set mister Ackerman spinning in his grave.

I attempted to overlay the straight ahead steering diagram with the full lock diagram so that the change in positions of the various components could be clearly seen as full lock is applied.

Apologies to the real engineers here for this amateur rendering.

There is a lot of engineering gone in to your steering set up! It makes a rack and pinion set up look quite basic, It must be hard to get all the friction and backlash out of all the joints in your steering set up
Fantastic technology I would like to try your set up!    (But I do like my steering wheel.) 

[Liteway]

Thanks. You are right about the importance of keeping each connection slack free as there are so many of them.
4 needle bearing sets
2 plain bearings
6 rod ends.
2 ball joints

Plain and needle bearing sets were the most troublesome.

A tiny bit of slack at each point could leave things feeling loose at the grips and that would be a real downer for a system that otherwise gives you a very direct feel for what the tire contact patches are doing.

I have zero slack and changes in direction at highway speeds are accomplished by just exerting a bit of palm pressure with no visible
movement required.

You could think friction might be a problem but its not. You can move the steering around with your thumb and fore finger if the wheels are jacked off the ground.

Dave. I think you can see the system could be adapted to foot operation as you suggested.



Later: I Don't begrudge your attachment to steering wheels, 2trike, I like em too.
This type of steering is best suited to very light single seaters and not much else.
Nonetheless, it offers up some real advantages which I won't repeat again as I've posted them elsewhere on the forum Ad nauseam.

[Liteway]

Over on the Captains build we were talking about the lack of self centering when near full lock.
I'm extending the discussion here because I don't want to put more entries in on his build page than he does.(Ha)

Anyway, this comes under steering tech more appropriate to tech threads.

That discussion had made me think about a weakness in my steering that might affect stability, self centering. Stability is acceptable, even pretty good, accept in brisk cross winds.
I would like more(at least some) self centering near full lock and more at road speeds which I think would help in crosswinds.

No doubt Suzuki did not envision the use of their of sport quad front end for cruising down the highway at 70 with occasional sprints much higher. Likely it was designed with quick turning and not high speed stability in mind. They had no idea some hillbilly whacko out in okla was going to drop it 4 or 5 inches, increase the track by 1/2 a foot and crank in a bunch of caster,tying to make it work on the street. Then top it off with some oddball steering arrangement. But hey, its not bad.

To the point.

I always thought that caster was where you get the self centering making it a key factor in stability. I must be wrong because I have much stronger self centering in reverse where the caster angle is negative to the direction of travel. What?

I also understand scrub radius should be a factor (main one?), But: I had to replace the bent front rims with some with 1/2" more positive offset which should increase scrub radius (as I understand or misunderstand the term). Neither self centering nor stability were affected.

Please enlighten me.




Later; I now understand part of my own question. Whether leaning the kingpin axis toward or away from the direction of travel, it tends to point the wheel that direction.
Its when the kingpin axis is vertical that the instability comes in. But As I observed out in the garage, negative caster is more effective at promoting direction stability than positive caster. So why don't we use negative caster? Ha. Imagine a chopper with negative rake.

Still trying to wrap my head around how scrub radius interacts with caster to produce other handling traits. I'll be back. I'm retired.

Need sometime away from the screen. Think I'll go out in the garage and overhaul my motor.

[captainamerica]

Just a thought, not related to you last question but did you ever think about trying an offset angle at your steering bell cranks, making them statically less or more then 90 degrees, so that one crosses center and the other doesn't depending on what way you turn. I'll see if I can throw something together in CAD this week to give you a better idea of what I'm talking about and maybe an idea of how much you could affect your ackermann with it. But basically I think you could transfer your ackermann inboard or at least allow yourself to adjust with with new bell cranks rather then new upright components.

I think the reason we use positive caster is because of the affect on camber when you turn in, not sure about this, just thinking about it off the top of my head. When I turn left the right tire camber increases in the negative (top in) direction because I am rotating around an angle that is tilted backwards on the caster, this also causes the left tire to have positive camber which will make both tires lean into the corner sort of the way a bike would and the way you want them to in my opinion. I think if you have caster like a shopping cart the camber will tend to to be in the wrong direction, where the bottom of the wheel will tuck under the and top will angle outward (visually at least) creating positive camber in relation to the way your try to turn. If you look at the way your left tire looks in a left turn, that would be the way your right tire would look with opposite castor in a left turn if you adjust your viewing position to be in front of the car looking back at the driver. Kingpin angle will also definitely have an affect on this, I will see if I can throw together a quick model of this sometime in the next week to put numbers to reality. Sorry if the explanation is hard to visualize.

I think that either castor direction will self center equally since they will both want to normally be at the point of least resistance which is straight forward where the castor line and the tire center are close to parallel with the direction of travel.

[Liteway]

Feb 10, 2016 12:04:31 GMT -6 captainamerica said:
Just a thought, not related to you last question but did you ever think about trying an offset angle at your steering bell cranks, making them statically less or more then 90 degrees, so that one crosses center and the other doesn't depending on what way you turn. I'll see if I can throw something together in CAD this week to give you a better idea of what I'm talking about and maybe an idea of how much you could affect your ackermann with it. But basically I think you could transfer your ackermann inboard or at least allow yourself to adjust with with new bell cranks rather then new upright components.

I think the reason we use positive caster is because of the affect on camber when you turn in, not sure about this, just thinking about it off the top of my head. When I turn left the right tire camber increases in the negative (top in) direction because I am rotating around an angle that is tilted backwards on the caster, this also causes the left tire to have positive camber which will make both tires lean into the corner sort of the way a bike would and the way you want them to in my opinion. I think if you have caster like a shopping cart the camber will tend to to be in the wrong direction, where the bottom of the wheel will tuck under the and top will angle outward (visually at least) creating positive camber in relation to the way your try to turn. If you look at the way your left tire looks in a left turn, that would be the way your right tire would look with opposite castor in a left turn if you adjust your viewing position to be in front of the car looking back at the driver. Kingpin angle will also definitely have an affect on this, I will see if I can throw together a quick model of this sometime in the next week to put numbers to reality. Sorry if the explanation is hard to visualize.

I think that either castor direction will self center equally since they will both want to normally be at the point of least resistance which is straight forward where the castor line and the tire center are close to parallel with the direction of travel.

---------------


Yes to your first question, and it would effect ackerman,but its a messier way (unintended consequences?) to get it than the usual way of simply reangleing the steering arms. By "new upright components" you did mean steering arms?. They are easier for me to make than bell cranks, one piece being cut from 1/4" aluminum plate as opposed to being welded up out of 1/2 dozen bits of steel. Reangleling the bell cranks would also mean fabrication of a new center tie rod to respace the plain bearings.

Anyway, I'm satisfied with the amount of ackerman in the steering, but its an interesting academic proposal that shows some flexibility in this steering type.

In response to my question about why we use positive as opposed to negative caster, your answer makes sense to me.


On the last point, the fact that I get more self-centering when pushing the trike in reverse where caster angle is negative in relation to direction of travel than forward where its positive is likely to be factors additional to caster alone. It is hard for me to visualize.

Maybe you can make an a workable 2 dimensional model. The three dimensional one out in the garage gives me a headache.

[noahkatz]

Feb 10, 2016 13:04:31 GMT -5 captainamerica said:

I think the reason we use positive caster is because of the affect on camber when you turn in...

That's a useful side effect but I believe the primary reason is to create trail which gives self-centering.

[captainamerica]

Mechanical trail can be created in both the front or the rear of the tire centerline vertical axis by using positive or negative castor, you really just want to get away from vertical so that your forces have greater moment arm to try and realign the tire with the direction of travel. The downside of this is that if your castor is to large for the weight of the vehicle the steering input required to turn will be strenuous on the driver. Scrub radius from the kingpin inclination is also a way of tuning the steering input required, if your vehicle can handle wheel spacers then a test could be done by just adding wheel spacer and seeing how much affect that has on difficulty of turning the steering wheel.

Technically a trailing wheel, lower mount behind the upper mount should be even more stable (wanting to realign with the current direction of travel), though its not this simple and its actually backwards to this from what I have read, but its effect on how the wheel grips the road while cornering would be at a disadvantage since castor in that direction will want to make the tire trip over itself by adding positive camber. Another part to add to this is that pneumatic trail always occurs opposite the direction of travel, so when you choose a mechanical trail to the front, the center line distance between the point on the ground that the wheel is rotating about and the center of pressure in the contact patch is additive, versus the reverse where they are negative to each other.

This is not a simple subject, but the rule of thumb that I have come across is the heavier you are the less forward castor you want, to the point of old heavy 50's automobiles that would use backwards castor to actually make the car unstable and easier to steer because the weight of the thing has a tendency to cause a lot of understeer trying to get it to turn through the corner. The only thing I can offer from real world experience is that I use between 7-8 degrees castor on a 1000lb trike and it seems to work quite well except in minimum corner radius, but I am not ready to attribute that to my castor angle over other possible things that might cause that.

[Liteway]

Feb 18, 2016 1:02:14 GMT -5 TheJoker said:

Self centering is also affected by Kingpin inclination angle. The more KIA, the more the car will want to go straight because as the wheel rotates around the KIA axis, it is trying to lift the front end of the car.

If you follow the end of a spindle's stub axle from the side view of the car, and made a line as it moves through the entire range of motion of the steering, you would see that the line it creates is an upside down "U" shape. The axle is at the highest point of the upside down "U" when the wheels are pointed straight ahead, which is where it wants to remain.

This article explains it better than I can.

www.motoiq.com/MagazineArticles/ID/1982/The-Ultimate-Handling-Guide-Part-8-Understanding-Your-Caster-King-Pin-Inclination-and-Scrub.aspx

Captain touched on this in his post, but I thought the KIA needed to be stressed a little further. 

Thanks Joker, that does clarify.

For those more new to the forum, Joker has built and uses his own form of sidestick steering.
Among other differences, his works from ahead of the front axle line as is general automotive practice, while mine works from behind, as commonly used on ATVs.
reversetrike.proboards.com/thread/174/light-trike

[Deleted]

I'm in the design phase of my reverse trike. It's really going to be more of a beefed up electric powered recumbent with an enclosed body. This type of steering system has a lot of the elements that I've been looking for. As someone who has never built a steering system before, I would love it if you could post some pictures or a quick video of how it works the next time you have your trike taken apart to help get the creative juices flowing.

[Liteway]

I later learned;
4 degree difference in angle between the front wheels was not sufficient for my trikes track and wheelbase and resulted in excessive tire scrub and understeer when cornering on a tight radius and steering that wanted to hold maxlock instead of self centering at the limits of lock as is normally the case. Steering arms should have been angled in a bit in relation to the kingpin axes to make that difference 6 to 8 degrees.


You would need to do your own diagramming and/or experimenting to find out what is optimal in your application.

I am making that change as I convert from an ATV to a CanAm Spyder based front end.

I'll post pictures when I'm done, about 50% complete after 75 to 100 hours of diagramming, mock ups, parts modified ,parts fabricated and cutting/grinding away the old suspension mounting tabs. (grossly overbuilt)

Ever bit the B---h I thought it would be.