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alevand
human power expert

USA
3541 Posts

Posted - 11/08/2015 :  06:05:20  Show Profile  Visit alevand's Homepage  Reply with Quote
I tacked the front end on the the Carp. I has about 7 inches trail, about where the rod is. A little more than I was wanting, but funny enough it has no wheel flop, but just the opposite, the wheel wants to be straight. I wanted to put internal elastomers in the tube for suspension, but doe to the placement of the steering linkage would have caused bump steer. 700x28c tire. I have a rod end ball joint on the top fastened with a coiled spring pin. I welded on two washers on each side of the tube for reinforcement. I had to grind half of it then away to to steer 90 degrees without the tube hitting the rod end housing.


I still need to finish weld it, weld on the brake bosses and steering attachment. I hope to be able to go down the hill today on it.

C:
Tony Levand

Edited by - alevand on 11/08/2015 06:09:11

Speedbiker
human power expert

USA
3835 Posts

Posted - 11/08/2015 :  11:16:39  Show Profile  Reply with Quote
Eagerly awaiting test results.
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alevand
human power expert

USA
3541 Posts

Posted - 11/08/2015 :  13:01:17  Show Profile  Visit alevand's Homepage  Reply with Quote
My toe is hitting the steering linkage and the CG is off. I need to make some adjustments. Ive got some old rod ends that are a little stiff. I'll try to make a video riding no hands.

C:
Tony Levand
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Jerry
human power supergeek

USA
1475 Posts

Posted - 11/08/2015 :  14:14:42  Show Profile  Reply with Quote
I am in the same boat as Thom, Awaiting the finished product, video, and results. Looks good so far.

I was thinking about remote steering on the a Rans also. Then I could run 2-559 wheels on it.
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alevand
human power expert

USA
3541 Posts

Posted - 11/08/2015 :  16:44:12  Show Profile  Visit alevand's Homepage  Reply with Quote
Video is uploading to youtube. I made the steering arm shorter on the fork, from 4 inches to 3 inches, its now clearing my toes. I checked the CG ,it seems OK, the bike is pulling to the right, I think I need to adjust the links on the fork. I rode it around, still not use to it. I use to lean to bike into turns, but there much less feedback. Probably due to the steering axis moving, it essentially cancels the trail and the moves further to the opposite side of the contact patch. I think it will work. It goes through gravel and bumps just fine. Had it up to 25 mph, no more shimmy. The 451 shimmied, starting at 18 mph but it could have been because the frame was cracked. It could get quite violent if I let go of the bars at speed. ..video 44% loaded...https://youtu.be/BHXnoicgONc

The uncompressed but abbreviated version is here:https://flic.kr/p/Ae5ehb

C:
Tony Levand

Edited by - alevand on 11/09/2015 03:30:24
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Jerry
human power supergeek

USA
1475 Posts

Posted - 11/08/2015 :  17:34:38  Show Profile  Reply with Quote
Cool video Tony. Looking good. I have so much to learn and a short time to do it!. Did you cut down your handle bars?
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alevand
human power expert

USA
3541 Posts

Posted - 11/08/2015 :  17:46:12  Show Profile  Visit alevand's Homepage  Reply with Quote
Not yet. Thinking of making them 1 inch on each side narrower, I'd have to change the brake handles to the reverse TT type, for that Id need a open tube on the end. These a custom bars. I made them from 7/8 x .028 tubing.

C:
Tony Levand
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Jerry
human power supergeek

USA
1475 Posts

Posted - 11/08/2015 :  18:13:06  Show Profile  Reply with Quote
They sure look good!
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Grant-53
recumbent guru

USA
554 Posts

Posted - 11/09/2015 :  11:58:11  Show Profile  Reply with Quote
The head tube angle and the fork curve giving the tire patch offset look good. The clearance issues and other adjustments should come along nicely. It took me a minute to realize the different definition of 'trail'. I enjoyed the video. Thanks
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stix
recumbent enthusiast

Australia
153 Posts

Posted - 11/09/2015 :  15:29:14  Show Profile  Reply with Quote
Can someone please draw me a sketch of how this virtual pivot steering works?

I have watched the video and the steering clearly works well but I could not figure out what was pivoting about what.

Stix

Peregrin on Birk (Birk Comet RT with full fairing)
Lightning F-40 (built around R-84 frame)
Soma Smoothie Upright
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Jerry
human power supergeek

USA
1475 Posts

Posted - 11/09/2015 :  15:51:53  Show Profile  Reply with Quote
Tony, is the remote steering rod under the speedometer tied into one side of the double steering linkage on the right side of the fork? Or is that an optical illusion?
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Speedbiker
human power expert

USA
3835 Posts

Posted - 11/09/2015 :  17:21:27  Show Profile  Reply with Quote
As Stix noted, this is not ordinary fork. Don't be fooled because it uses an old fork. Jerry mentioned headtube angle, but there is no headtube. If you go back 8 years to when we first saw this, my brother called it "virtual axis" steering. With the top of the fork riding in a spherical bearing, and the lower part swinging on lower links that are angled about 45 degrees, when some kind of linkage twists the fork one blade swings forward and the other swings back. The length and angle of the links create a virtual axis about which the assembly swings, and creates trail. My brother mapped it all out in a motion file using Unigraphic CAD. I think Tony has a lot of adjusting to do to optimize it. Just don't picture it turning in headset bearings because that doesn't begin to explain how it works. With the use of CAD my brother mapped it out to have convention, if virtual geometry. He was able to run it thru various simulations to test it. Too bad his motion file doesn't run any more. This is complex stuff.
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warren
human power expert

USA
6470 Posts

Posted - 11/09/2015 :  17:35:16  Show Profile  Visit warren's Homepage  Reply with Quote
The best example of virtual pivot steering that I can find on the web is this page with photos of rohorn's motorcycle.
http://thekneeslider.com/recumbent-racer-virtual-hub-center-steering-closeup-with-video/
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Jerry
human power supergeek

USA
1475 Posts

Posted - 11/09/2015 :  18:05:37  Show Profile  Reply with Quote
So, there is a linkage from the handle bars to the front fork? It looks to me like a linkage rod from the side of the handle bars to the front fork. Then the fork is tied into the two steering linkages. Maybe I missed something.

I want it! I think if I can see it up close and personal, I can build it. Maybe not.

Edited by - Jerry on 11/09/2015 18:07:46
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warren
human power expert

USA
6470 Posts

Posted - 11/09/2015 :  18:14:50  Show Profile  Visit warren's Homepage  Reply with Quote
Looks like basically the point where the two control rods meet virtually is the virtual pivot point. I'm thinking a line drawn from the pivot at the top of the fork through the virtual pivot point to the ground is the forward point of measure for trail calculation. Measure from the contact point of the tire to the forward point for the trail. Does that sound right Tony?
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warren
human power expert

USA
6470 Posts

Posted - 11/09/2015 :  18:21:12  Show Profile  Visit warren's Homepage  Reply with Quote
Yes there is a remote steering rod from the handlebars that controls the steering.

I think Robert Horn feels like we dissed him on this site and that's why he doesn't post here. Probably because nobody could think of a good reason to use it. It's a cool idea, and I think Tony has found a good use for it.
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alevand
human power expert

USA
3541 Posts

Posted - 11/09/2015 :  19:13:24  Show Profile  Visit alevand's Homepage  Reply with Quote
There is a ball joint at the top of the fork that's attached to the frame. 6 inches down the fork is attached two ball joint rods, one on each side, it makes whats called a four bar linkage, like a "V" shape. If it were a V then it would be a stable triangle, but the top of the V is truncated, a trapezoid. The pivot point is where the line of action of the two rods meet, the apex of the V, which changes with motion. Draw a line from the ball joint through the virtual pivot and that is the steering axis. The front wheel is attached to the top of the trapezoid.

Yes Jerry, that's right the steering arms are 3 inches long.

Video is uploading...https://youtu.be/fzPwvj2qGMM


C:
Tony Levand

Edited by - alevand on 11/09/2015 19:15:28
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Speedbiker
human power expert

USA
3835 Posts

Posted - 11/09/2015 :  19:25:51  Show Profile  Reply with Quote
That's of course right, Tony. Big kudos for just understanding it, let alone shade tree engineering it. I worry a little about the link rods being attached so high up and not appearing to be in line between the top bearing and the axle. But that is only because I haven't totally mapped out the motion in my head. Nor will I try. Similar to the I-lean tilting trike, I would have to build it to get my head around it. You guys can talk about "out of the box" all you want, but whether Tony got inspiration from my brother or that dude who built the recumbent motorcycle, Tony is making it happen.
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Jerry
human power supergeek

USA
1475 Posts

Posted - 11/09/2015 :  20:18:29  Show Profile  Reply with Quote
That is about what I imagined it was. I just could not make out the ball joint in the head tube. I don't know who came up with what, but I like it and plan on trying it out. Thanks for sharing Tony.
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Grant-53
recumbent guru

USA
554 Posts

Posted - 11/09/2015 :  21:02:34  Show Profile  Reply with Quote
We are used to calling the fork angle the head tube angle but in this case there is just the single joint. The fork position is determined by the non parallel sides of the trapezoid. It's tricky trying to describe but I think I can see how it might make the steering feel more consistent or 'linear' through the range of motion. It's a little like trying to map out the motions of a non parallel link suspension in a different plane.
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Speedbiker
human power expert

USA
3835 Posts

Posted - 11/09/2015 :  21:39:02  Show Profile  Reply with Quote
Right. The reason we designed ours was with the lower links mounted below the axle it provided very solid fork geometry no matter what loads from any direction might affect our streamliner. Fork flex can cause many problems with a streamliner. Also, we designed ours to also have suspension, and by managing those pivot points we had suspension with no change in geometry. Add that to your visualizing how it all works. Oh, we planned fwd for all the same reasons. Drive and braking forces don't disrupt the geometry.
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Speedbiker
human power expert

USA
3835 Posts

Posted - 11/09/2015 :  21:40:45  Show Profile  Reply with Quote
Did someone accuse me of not "thinking out of the box"? And remember, this was 8 years ago....
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Jerry
human power supergeek

USA
1475 Posts

Posted - 11/10/2015 :  03:31:13  Show Profile  Reply with Quote
Thom, no one accused you of not thinking outside the box. You are just like I am, it is not what you are saying, it is sometimes how you are saying it. I will say this, you do know what you are talking about. Just sometimes you are like Sheldon on The Big Bang Theory, you need a back rub and sung the song here Little Kitty, Soft Kitty! lol

And, Grant-53 said head tube angle, not Jerry.

Edited by - Jerry on 11/10/2015 03:33:15
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alevand
human power expert

USA
3541 Posts

Posted - 11/10/2015 :  03:55:12  Show Profile  Visit alevand's Homepage  Reply with Quote
Thom, Yes its better in that respect to have the links as low as possible, but it restricts turning. There is less bending moment on the fork than with the head tube. The closer the the ends of the links are to the pivot the less trapezoid effect there is. I had 36 inches or more of trail on some of the mule tests with mbb and fwd. The links on the race bike are 3 inches above ground. There is only 60 lbs weight on the front tire, the next test will be with braking. Yes, I got the idea from the guy that built the Harley powered motorcycle (Rohorn) in 1990.

http://rohorn.blogspot.com/

C:
Tony Levand
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PUGZCAT
recumbent enthusiast

Canada
466 Posts

Posted - 11/10/2015 :  04:08:08  Show Profile  Reply with Quote
Eating a Snickers bar wouldn't hurt either. Nifty way to chop some front end height on the liner.
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Jerry
human power supergeek

USA
1475 Posts

Posted - 11/10/2015 :  04:12:22  Show Profile  Reply with Quote
Tony, It looks as if Rohorn's fork is more vertical than the Carp's. What is the angle of your fork, 15-20 degrees? Is his fork angle the reason his doesn't have much trail?
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