Australian Streamliner Bike Build

[Jon]

Not all things in agriculture are "agricultural".

I was involved in the development of one of the first self steering RTK GPS tractors.
80 tone could keep on line within about 2" either way 24/7.

Have a look at Marlo's Streamliner, almost exactly the same concept.
No pumps, valves etc, two double acting rams, one is working as master, the other as slave.
The same concept has been used to replace long linkages on machinery for ages.

Cheers
jon

[Rex Schimmer]

Maj,
You are sure right about present day tractors, I rent a John Deere to cut my small field and if you notice there is no real connection between the steering wheel and the front wheels, the feed back link is the driver vision, the steering wheel position kind of just wanders around!. At 20 mph they are scary!! Now if you do something similar to the system used on Marlo's car you have a much better system if you do the details correctly.

Rex

[bones]

Jon
  Could yo put up a few pictures of the front suspension, I can't see where the pivot for the wheel is.
 I was expecting more like the Buddfab with a swingarm ( I'm only a sidecar rider)
  Keep up the good work.  I'll get back onto mine soon.
    cheer    Bones

[Jon]

Rex; like ive told a few people and they've said back to me; the rules are the rules. Linkages it is.

Bones; the top pivot only exists in my head, it will go steel this weekend.
Think a monoshock rocker, shock behind the wheel and a spherical bearing on the other end of the rocker attached to the top of the yoke.
I don't have enough width to get a shock up each side of a car size wheel.


Like everything the answer is pretty simple when you stop doing what you are doing and stand back.

Thanks DaveL for making me start again.

Will throw up a Post-it note engineering drawing tonight.


Cheers
jon

[Jon]

More info from Woody as he refines the model to reflect what I've built;





"Just fits" is good, isn't it?

Cheers
jon

[DaveL]

Jon, by 'familiar' I was referring to my understanding of the concept of 'virtual' pivots rather than the specific applications of it. That said, yours is probably the 8th or 9th time I've seen it used in an LSR vehicle.
As for eliminating bump steer with strictly a mechanical system, you would have to determine what level of complexity you're willing to except. Some simple setups almost eliminate it, others are fine when the wheel is straight ahead but suffer slightly when turned, only a few totally eliminate it. Naturally they're also the most complicated. I'll concede that a small amount of bump steer is probably acceptable but personally, I'd prefer to cancel it completely. The Aircraft strut style hinge linkage is also a good choice.
Good luck with your project!
Dave

[Koncretekid]

Jon,
It took my old head a while to figure out how your bike will steer.  It looks to me that the whole wheel moves back and forth, and turns because of the geometry of the lower links.  Does this not move the tire contact out of line with the centerline, and hence the center of gravity, of the bike?  If a gust of wind hits the left side of the body, causing the body to lean to the right, you have to steer to the right to compensate, which moves the body further to the left.  I think I'd want to find a big hill and coast it down to try out that concept.  I may be wrong, but I wouldn't want you to get to the salt flats to find out.

On my little bike, I got a weave at 125 mph, for no apparent reason, so I know these things can happen.

Tom

[fredvance]

Tom check your neck bearings, if they are too tight it will make the bike weave.

[kiwi belly tank]

As you know Jon, I'm a streamliner guy, but it seems to me you are all tangled up in some confusing stuff here & from this end I cant see the whole picture..
The hydraulic slave cyl set up was tried on the Maro Special & found to be undesirable. It is also "illegal" under SCTA rules.
Not to try & re-engineer your wheel, but look at this from a car guy mind.
A single leading arm from behind the wheel to a kingpin in the center of the wheel with no KPI & caster of your choice & a stub axle.
Coil over shock mounted behind the wheel.
Steering arm on the stub axle, drag link back to the handle bar shaft with a length the same as the leading arm.
Simple to build, no bump steer & a lot less stuff you are having to build here.
There would be minimal caster change but is that an issue?
  Sid.

[rgn]

Looking at the rear wheel detail drawing, it looks like you are considering steering it from the rear?  lol...  Sorry...

[Jon]

I agree Sid, KISS it is.
You have "Engineering Drawings" in your email.

Hopefully the rear end stays behind me Sid.
When I was young I did speedway for a while, used to have a Roardrunner decal on the front guard and Wile E. Coyote on the rear, contrary to the cartoon Coyote did catch the Roadrunner a few times.
Cheers
jon

[wobblywalrus]

Jon, the streamlined shell has a good shape.  How do you see out of it?  Is there a canopy?

[Jon]

Thanks Wobbly.
The canopy runs from the nose back to the front of the roll cage, from the top of the wheeltub up.
There is a paintjob drawing a couple of pages back that shows the rough outline of the canopy.

Cheers
jon

[kiwi belly tank]

Re email.
I dont see why you need to steer it from both sides.
Whats locating your fork?
The extreme length difference in rocker arm & drag link will give extreme bump steer.
Looks to me like you need to take off your bike hat for a while & put on your car hat mate! Might help if its got corks on it.
  Sid.
 

[Jon]

Thanks guys

Tom; didn't mean to snub you sorry, the wheel does move away from the centerline of the bike in the opposite direction it turns, all conventional fork bikes do due to the trail. It's only a slight movement at low input angles and obviously bigger at bigger steer angles.
At slow speed when trying to balance the bike I think it will help, at higher speeds I (hopefully) will be using lower input angles, will also be counter steering.

Sid; the two arms are to make the hinge link plate work (Thanks DaveL for the prompt)

I wasn't hiding anything when I didn't put my "engineering drawings" up, other than most of my stuff is done from very basic line sketches on the back of recycled paper while on the phone at my desk.

For everyones amusement;
Top view;

I haven't drawn the suspension rocker or shock that supports the spherical bearing.

Side view;

You can hardly tell the difference between my drawings an Woody's .


OK, this is how it works;
Handlebars pivot on a vertical pivot (obviously)
The "hinge plate" hinges from the handlebars and has the tie rod bearings attached to the bottom.
This allows the two tie rod ends to move back and forth a little as a pair but they are at the same angle to each other as the handlebars.
The two rods go forward to the yoke and make the yoke turn the same amount as the handlebars.

When the suspension moves it will be in arc, with only one arm this would create bumpsteer unless the geometry is perfect.
It's pretty easy to get 0 bump with the wheel straight ahead but a bit more difficult to get it over the full suspension and steering travel matrix.

By having two arms that input steering by their relative positions rather than one arm that input's steering by it's actual position allows the use of the hinge plate to absorb the wheel travel arc.
The hinge plate shape is going to be a little tricky as I want the rose joints to be in line with the handlebar pivot when the wheel is at normal ride height, it will move back slightly in both bump and rebound suspension travel directions.

Simple, different but simple, two words that people use about me.

Cheers
Jon