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Old 08-20-2008, 11:10 AM   #121
Bad Cat Racing
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Quote:
Originally Posted by HogWild
The other negatives are the un-sprung and overall weight. A leading link setup looks much better in those respects.
Disagree.

On a street based rig the hub center steering front end is always -considerably- lighter than the leading link front end simply due to the amount of mass saved alone not having to have a bulky machined rim/caliper carrier with wheel bearings. in the unsprung mass.

You have in unsprung mass on Hub Center Steering not factoring in the tire/rim which is constant in both configurations.

~ A Upright
~ A Brake Rotor
~ A Caliper and some pads
~ One or four wheel nuts
~ A couple heim joints

Now in Leading Link you have

~ A Solid Axle plus centering spacers and axle bolts
~ A Machined wheel/brake rotor carrier
~ A Brake Rotor
~ A Caliper
~ A Caliper Stay
~ The Leading Link

The hub center wins every time when it comes to the amount of unsprung mass moving up and down on the end of a shock really fast. Having personally held and felt both versions in my own two hands, leading link is a pig for a HPS. Our CSR has leading link because it's builder/driver prefered to throttle/compression steer his rigs into and out of corners. And when the rig is sideways, the tire profile is flat in relation to the asphalt even with the bars turned.

It's not -our- driving style, hence we're moving to an LCR.

Quote:
Originally Posted by HogWild
Again, for anything going where there are bumps, weight is definitely bad. The one thing that I like about the center hub system is that the tire stays level while turning. That's definitely nice if you have a wide and flat profile tire up front.
There are different hub-center systems than the two I pictured. The system on the green '333' Kawi that ran Pikes Peak this year for example has a great deal of travel and is much more compact than the two long wheelbase HPSes pictured.



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Old 08-20-2008, 11:57 AM   #122
claude
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Opinion wanted on hub center design.
Is it possible to add caster without as much concern of camber changes when turning when using wider front tires by placing the spindle itself behind the line of the ball joints (steering pivot points whatever that may be) when viewed from the side? If so where woudl the compromose be? In other words can the ball joints be almost verical and the spindle farther back?
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Old 08-20-2008, 04:07 PM   #123
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Quote:
Originally Posted by Bad Cat Racing
The hub center wins every time when it comes to the amount of unsprung mass moving up and down on the end of a shock really fast.
Not true, especially for a rig built to go off-road. If what you say were true, hub center systems would dominate off-road sidecar racing, where suspension performance is even more important than horsepower. My comments are in reference to rigs capable of good performance in off-road conditions, since that's what Pezz_gs seemed to lean towards when he brought up the subject. Street only rigs are a whole different story.

Your hub center vs leading link comparison list misses several important items (such as the fender), and it implies weight differences that are insignificant or don't exist. Of course a poorly designed system of either type can be inferior to a well designed system of the other type. Lots of things can be done less than optimum. For example, the orientation in which the shocks are mounted is important when considering unsprung weight. Mounting the shock “body” end on the swing-arm and the “shaft” end on the forks is bad because the shock body weighs a lot more that the shock shaft. So, the shaft should always be on the moving part of the suspension. The road race rig you pictured earlier (here) would not be a good setup if you wanted the best suspension performance because the shocks are mounted upside down.

Also, if unsprung weight is an important issue for someone on a dirt going rig, the biggest factor is the tire and wheel, not leading link v.s. hub center. The front tire on my V-Rod rig (not even including the wheel) weighs about 4 times more than my swing-arm/axle & nuts/brake components/hub/rotor/shock shafts. And it’s also about 4 times heavier than the front wheel and tire combined on my Honda motocross sidecar. So there’s a lot more weight to be gained or lost in the tire/wheel selection than in the steering/suspension selection.

I see two good reasons to pick a wide flat profile auto type tire for the front of a dual sport sidecar rig:
1) Better turning and braking performance on pavement or very hard dirt (minimal loose dirt on the surface).
2) Better floatation in soft sand.

I see many reasons to pick a narrow rounded profile motorcycle type tire for the front of a dual sport sidecar rig:
1) Lighter weight tire and wheel.
2) Better suspension performance due to less weight.
3) Better turning and braking performance in medium to soft dirt.
4) Easier steering on uneven surfaces (due to contact patch not moving as much from one side of the tire to other).
5) Easier turning than wide tire when with leading link forks due to edge lifting issue.
6) The front wheel that came with the motorcycle will probably work fine, keeping overall costs to a minimum.

For a typical dual sport sidecar, I see little or no reason to go with a wide front tire or a hub center system. And for anyone sensitive to costs and fabrication complexities, it seems pretty clear which way to go. On the other hand, if cost is no factor, and you love a challenging project, and you want the most eye-catching dual sport rig around, go for the wide tire and hub center!
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Old 08-20-2008, 04:08 PM   #124
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Quote:
Originally Posted by Bad Cat Racing
Disagree.




Do you have any more pics of that front end?
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Old 08-20-2008, 04:21 PM   #125
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Quote:
Originally Posted by Pezz_gs
Do you have any more pics of that front end?
Here's their website:
http://www.les-marluches.com/
and a few photos here also:
http://www.advrider.com/forums/showp...30&postcount=1
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Old 08-20-2008, 04:22 PM   #126
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Quote:
Originally Posted by HogWild
Thanks Scott
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Old 08-21-2008, 09:51 AM   #127
Bad Cat Racing
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Quote:
Originally Posted by HogWild
Not true, especially for a rig built to go off-road. If what you say were true, hub center systems would dominate off-road sidecar racing,
Didn't say offroad... said, "On a street based rig the hub center steering front end is always -considerably- lighter..."

Quote:
Originally Posted by HogWild
Your hub center vs leading link comparison list misses several important items (such as the fender),
Carbon kevlar, a few ounces. I bag them myself... so I know.

Quote:
Originally Posted by HogWild
Mounting the shock “body” end on the swing-arm and the “shaft” end on the forks is bad because the shock body weighs a lot more that the shock shaft. So, the shaft should always be on the moving part of the suspension.
One would assume that if one is desiging a front suspension unit one knows the 'gradeschool basics' of conserving unsprung mass. I know it, you know it... maybe not everybody here does. But if anybody here is going to tackle designing their own front suspension unit, leading link or hub center, they better hit the books first.

Quote:
Originally Posted by HogWild
The road race rig you pictured earlier (here) would not be a good setup if you wanted the best suspension performance because the shocks are mounted upside down.
That's the front end on our CSR. You can't flip those Koni shocks upside down, you'll blow the seals out of them and the shim stack/popoff valve LE installed will not pop off correctly or stick. Even the modern 'championship winning' LCR F2 with it's 1000 dollar a unit Maxton coil-overs are mounted in the same orientation. Yeah, more mass on the bottom of the spring, but hey, the shock is designed to work in that orientation, not the other way around. They're pulling 115mph flying laps around the Isle of Man. Something must be working right in the front end with the shock 'right way up'.




And keep in mind, where as you measure your suspension travel in inches, we measure ours in the 22 to 24mm range, even on the street a HPS is only going to have about three inches of travel at the very max.

It's a tradeoff. That's why leading link sucks on the street. You go to hub center and you have a better selection of dampers that can be fitted in different orientations. Hell, you can move the whole unit inboard into the chassis and use a bellcrank/pushrod if you don't want to go direct link. Vary the length of your bellcrank and you can even use a longer stroke on your damper to get better resonse out of your suspension.

Quote:
Originally Posted by HogWild
For a typical dual sport sidecar, I see little or no reason to go with a wide front tire or a hub center system. And for anyone sensitive to costs and fabrication complexities, it seems pretty clear which way to go. On the other hand, if cost is no factor, and you love a challenging project, and you want the most eye-catching dual sport rig around, go for the wide tire and hub center!
And if you're on the asphalt which is what I was originally addressing, Hub Center is the only thing that makes sense.
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Old 08-21-2008, 12:49 PM   #128
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Quote:
Originally Posted by Bad Cat Racing
And if you're on the asphalt which is what I was originally addressing, Hub Center is the only thing that makes sense.
You're talking street and I'm talking dirt. Pezz_gs asked about front end types in regards to his dual sport type application, which includes off-road with some big nasty bumps and holes. Larryboy seemed to be interested in the same thing. So I was trying to be helpful to them, proving my views based on their questions. I didn't see anyone ask which setup is best for street only or road racing.

If money was no object, I wanted to take on a big project building a rig from scratch or heavily modifying an existing rig, and I was going to use it strictly for pavement, I would be all over hub center steering.

On the other hand if I were working with an existing telescopic forked rig where price, fabrication complexity, decent street performance and very good off-road performance where important factors, I don't believe that hub center would be the best choice.
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Old 08-21-2008, 04:22 PM   #129
claude
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Would not you all agree that the compromises for an all around street rig or especially a recreational dual sport rig are much greater than those of a specialized rig for racing on dirt or asphalt?
Gues my last question was ignored huh?
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Old 08-21-2008, 04:38 PM   #130
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Quote:
Originally Posted by HogWild
Larryboy seemed to be interested in the same thing. So I was trying to be helpful to them, proving my views based on their questions.

The banter is very helpful...keep it up.

I'm trying to get my ducks in a row on my project. I really want 2WD and know how to get there, but that leaves the front end in question. I'm not going to get huge wheel travel from A-arm suspension on the hack and the bike drive wheel...6 inches of travel is about all I can expect..so that leaves me questioning a front end. If I could get 5-6 inches of travel out of a hub center design that is strong enough to be bottom'd all day long, that might work. A leading link front with 8-10 inches of travel strapped to the limited range of the other two wheels might not work so well.

Then there is ground clearance..most of the hub center designs I've seen have the lower spindle mount just about on the ground..so I might be better off building my LL and limiting travel to match the other wheels...yup, I think that is the way to go.
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Old 08-22-2008, 04:03 AM   #131
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Quote:
Originally Posted by larryboy
Then there is ground clearance..most of the hub center designs I've seen have the lower spindle mount just about on the ground..so I might be better off building my LL and limiting travel to match the other wheels...yup, I think that is the way to go.
I followed this discussion al littlebit and also believe an “off-road” hack is normally better of with a leading link for the same reason. So let’s start to confuse everybody and have a look at this pic.



I uploaded some more pictures right here.

http://www.advrider.com/forums/showp...&postcount=663

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Old 08-22-2008, 04:53 AM   #132
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And just in order to stay on-topic , some pics of my single-arm-leading-link:





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Old 08-22-2008, 06:48 AM   #133
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Quote:
Originally Posted by larryboy
...I'm trying to get my ducks in a row on my project. I really want 2WD and know how to get there, but that leaves the front end in question. I'm not going to get huge wheel travel from A-arm suspension on the hack and the bike drive wheel...6 inches of travel is about all I can expect..so that leaves me questioning a front end. If I could get 5-6 inches of travel out of a hub center design that is strong enough to be bottom'd all day long, that might work. A leading link front with 8-10 inches of travel strapped to the limited range of the other two wheels might not work so well.

Then there is ground clearance..most of the hub center designs I've seen have the lower spindle mount just about on the ground..so I might be better off building my LL and limiting travel to match the other wheels...yup, I think that is the way to go.
actually, I find limited sc wheel travel combined with much more travel on the bikes wheels works pretty well. If you really intend to dualsport the Suzi you could try to fit links and a longer shock to give more travel and a slightly softer ride to the rear and build what you want into links on the front and it may work out fairly nicely...

Claude has often warned against tall suspension on a rig allowing it to bounce over in a corner. While I think those concerns are exagerated, a long travel, soft sidecar suspension can contribute to dive in left turns and wallowing in general, where as stiffening and/or shortening it a bit allows the bike suspension to soak up most of the bumps with out the dive or wallowing back and forth. Claude prefers to stay away from long travel suspension and use a sway bar to mitigate these traits(if I understand correctly-I haven't yet tried this approach).

While I am enamored with the hub center front end, particularly linked to a steering sc wheel set far forward, I suspect a link front end with modified suspension on the rear and sc wheels will be a more practical approach for what you want to do.
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Old 08-22-2008, 09:27 AM   #134
claude
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VERNON 'THE RED MENACE' WROTE:
>>Claude prefers to stay away from long travel suspension and use a sway bar to mitigate these traits(if I understand correctly-I haven't yet tried this approach).<<

Not totally true as we do quite a few dual sport based rigs. However, for the street , especially if one likes to run hard in the twisties, a swaybar is like night and day as far as stability and basic handling goes. One end of the swaybar can be disconnected easily when the rig is taken into the rougher stuff.
One well known rigger will not even mount a sidecar on a tall softly sprung dual sport type motorcycle. His reason is lack of stability on the street. It isn't the right handers but the lefties that potentially can be the issue.
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Old 08-22-2008, 02:46 PM   #135
Bad Cat Racing
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Quote:
Originally Posted by claude
One well known rigger will not even mount a sidecar on a tall softly sprung dual sport type motorcycle. His reason is lack of stability on the street. It isn't the right handers but the lefties that potentially can be the issue.
Put some velcro along the bottom leading edge of the sidecar tub and throw a couple kneepucks down there.
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