Leading Link Q's
OldNick
Posted 12/19/2015 2:01 AM (#87162)
Subject: Leading Link Q's


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Hi guys. I am actually a noob triker. I hope I will be treated kindly.Respect I have to earn!

If the LL can lower the bar force in a turn, how is stability maintained and how is head shake stopped? So far everything tells me the two are incompatible.

A bike shop guy, who will make no money from it, said I should look into LL, as it is "like power steering". There is a guy in my city (Perth Western Australia) who makes them for side cars and has made maybe 20 or so. Not cheap, but I am interested. One beauty is the guy's setup is certified with the traffic people,so while I still have to get a permit, no Engineer's cert is needed.

So. From what I understand, the LL suspension will overcome the handlebar force when cornering, by drastically lowering the trail compared to a straight fork set with extra rake for stability.I have seen diagrams showing why and spoken to the maker above (NO Not Him!..the guy I mentioned above :D).He said he has had trail as low as 20mm and it really eases the steering.

Thanks for any help or info

Nick


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Sidewise
Posted 12/20/2015 5:25 PM (#87181 - in reply to #87162)
Subject: Re: Leading Link Q's



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Location: NJ The Garden State
Us sidecar folks are generally a friendly bunch so your questions are welcome here. I have LLs on my ST1100 EZS Sidecar outfit. I do not pretend to understand the dynamics but the reduced trail dramatically reduces steering effort; although not like the "power steering" exaggeration, especially running 175-65X14 front tire. The more sturdy construction reduces flex which contributes to head shake in telefork scenarios. As shake is usually not completely eliminated but more readily controlled because of the reduced effort, a dampener is still required to mask head shake completely. I have never seen a trike here in the USA with LLs and trikes have become quite popular with our aging riders.
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OldNick
Posted 12/20/2015 5:37 PM (#87183 - in reply to #87162)
Subject: Re: Leading Link Q's


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Ok I get that. Makes sense.

I have seen a few photos of trikes with LL and pages for trikers to design them.

Nick
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jaydmc
Posted 12/21/2015 11:22 AM (#87188 - in reply to #87162)
Subject: Re: Leading Link Q's


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Leading links reduce trail on the front end, they are also stiffer then traditional forks however the last couple of decades forks tubes have gotten much larger so the advantages of a link are not what they use to be. You did not say what bike you are working with. As to a front end shake, often making sure your mounts are not flexing, you do not have loose steering head bearings and the alignment is correct front end shake can come close if not entirely go away. A flat profile tire not the front can also help.
Jay G
DMC sidecars
www.dmcsidecars.com
866-638-1793
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Hack'n
Posted 12/21/2015 1:19 PM (#87190 - in reply to #87162)
Subject: Re: Leading Link Q's



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Auto/flat tread front tires will also follow seams in the pavement and are wiggly on grooved pavement.

Lonnie
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OldNick
Posted 12/22/2015 9:16 PM (#87201 - in reply to #87162)
Subject: Re: Leading Link Q's


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Thanks for all the answers.

So in the trike world there is still the strong feeling that unraked forks are bad news. Iagree that the forks are huge compared to what I remember from my younger daysn and I am sure that makes a huge difference. My concern is not head shake, as I have a raked clamp system. My trike BTW is based on a 98 Honda Valkyrie, with roughly 60mm diam forks.

My concern is why I have to have rake, and really push those bars to get around a corner, yet LL with tiny rake can be so steady.

As I now understand from you guys, the straight forks are not meant to take the twisting and side forces and therefore will twist and spring.LL's stiffness help the setup not flex.

A question: Why not simply brace the front forks of a straight setup? Is there some mother stuff going on here?

Ironically, I reckon some of the trikes with LL forks look as if they do not have the brace loop that goes behind the front wheel. To me that will weaken what rigidity you get from LL. (?)

I am not sure about the flat/auto tyre. I see Hack'n that you say a square profile will cause shake. Jaydmc, are you saying that a square profile helps on the _rear_ but not mon the front? HAH! If so my trike iks OK, it has 10" wide tyres on the rear. The front is an Avon Cobra, definbiteky not square.

Nick
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fastjoe
Posted 12/23/2015 4:17 AM (#87204 - in reply to #87162)
Subject: Re: Leading Link Q's



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Location: Eastern WA
You can remove ground trail from conventional forks by using tripple trees that change the distance the the fork tubes are in front or behind the steering stem (offset) or the angle the fork tubes are held at in relation to the steering stem (rake) or a combination of both methods. This is what raked trees are. The offset and rake (angle of the fork tube in relation to the steering stem) have been altered and the result is less measured ground trail and less force required to turn the fork assembly while negotiating a turn. There are also ways of changing the offset at the axle when altering the trees isn't a viable option which results in less ground trail but you seldom see this done on larger bikes..
A leading link front end with the same ground trail as a conventional fork would steer just as hard as the conventional fork with the same ground trail would. The contact point where the tire meets the road is the same distance behind the pivot axis of the steering stem on either fork if the ground trail is the same. Because of that it takes the same amount of force to drag the tire sideways across the pavement when you turn. Don't know if any of this is of any help or not.

This is not to say that a correctly engineered and built LL fork does not have the potential to be a better fork.
They really do have the potential to be a better design if the engineer knows his stuff. It's just that sometimes some things like how much something is different depends on the persons individual expirience.
We often describe the raked trees on our hack as power steering. It's not really accurate but the steering is noticably easier with the substancial reduction in trail than it was when the original motorcycle tripple tree was on it. Multi track vehicles don't need much ground trail. Motorcycles are a completely different animal, they need 3-4+ inches.

You might find this article interesting. It shows that rake really has little to do with trail: http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

Edited by fastjoe 12/23/2015 4:34 AM
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cleatusj
Posted 12/23/2015 7:49 PM (#87212 - in reply to #87162)
Subject: Re: Leading Link Q's



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Wider bars or ones that have your hands flatter than upright, will change your leverage, so that steering seems easier.
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OldNick
Posted 12/23/2015 8:29 PM (#87213 - in reply to #87212)
Subject: Re: Leading Link Q's


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The Valkyrie's bars are pretty wide (34"?) and in fact so wide that I really have to reach to get full lock, but yeah quite high, real cruiser bars, but not "sit up and beg" (I could never see how anyone could _ride_ a bike with apehanger bars, let alone for any distance. I inadvertently set them too far forward and really felt it, as they were naturally higher as well. So if I get some bars I will bear in mind that slightly lower bars would help. Thanks.

Nick
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OldNick
Posted 12/24/2015 8:09 AM (#87218 - in reply to #87162)
Subject: Re: Leading Link Q's


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So I thought about some trikes I have seen and even more so outfits and I recall bars that were made long, rather than wide; they swept back toward the driver rather than out an up.SOme of them IIRC almost had you leaning on them, and they swept across your knees.

While moving the bars forward made them feel worse, it did not occur to me to move them back past their original position. But you guys and my images of outfits made me think. SO I moved the bars back a bit at a time and found a spot.Nice! A whole new world of ease and confidence.

So I owe you guys thanks. I get the impression that sidecar guys are less about cool and more about a good ride!
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