Skiri251,
I think the pegboard mount would be great. Would give you lots of adjustment capabilty. I am not in Europe and my sidecar is mounted low on the right side of the bike. I'm not sure of all the dynamics involved but on my setup the bike tends to lean slightly to the left causing a slight left hand turn while on a level ground. I believe that with the low mounting points, the lateral forces of the sidecar frame (front pulling out, rear pushing in)together with the bike's steering geometry cause this slight left lean. I found that by scooting my butt and shifting my weight to the right side of the saddle as far as practical the steering would pretty much straighten up. So it stood to reason shifting the weight pushing down on the mounts to the right would do the same thing. So I moved the front to the right and it helped. Still has a slight left pull but not enought to warrent modifing the mounts. However, If I had the pegboard mount system I'd sure try other adjustments. I like that idea.
Roy
Originally written by uralsharps on 8/29/2007 4:51 AM
Skiri251,
I think the pegboard mount would be great. Would give you lots of adjustment capabilty. I am not in Europe and my sidecar is mounted low on the right side of the bike. I'm not sure of all the dynamics involved but on my setup the bike tends to lean slightly to the left causing a slight left hand turn while on a level ground. I believe that with the low mounting points, the lateral forces of the sidecar frame (front pulling out, rear pushing in)together with the bike's steering geometry cause this slight left lean. I found that by scooting my butt and shifting my weight to the right side of the saddle as far as practical the steering would pretty much straighten up. So it stood to reason shifting the weight pushing down on the mounts to the right would do the same thing. So I moved the front to the right and it helped. Still has a slight left pull but not enought to warrent modifing the mounts. However, If I had the pegboard mount system I'd sure try other adjustments. I like that idea.Roy
Thanks for the explanation.
The beemer free leaner site also says:
"A few designs also had the rear mount closer to the sidecar (offcenter with the engine) while the front mount remained centered about the engine."
So there must be something to off centered mount.
There is not much room for the peg board in the rear but I will try to accomodate as much as possible.
Actually moving rear pivot to the right gives me more right side lean angle!
Two birds with one stone, hopefully.
I see, it's not just the sitting forces we're dealing with is it, especially when you let things flex around a bit...
how heavy would you say your car is, uralsharps? 500lbs? less?
I think I want to try to make an armature that curves down under the pipes for better clearance, but that would also lessen the amount of lean I can get before scraping the arm... but I know I can't put 3" aluminum I beam under there and get any lean, even with the high clearance of the GS's...
see? we're still talking shop here ';-)
The forward mount Should be as high as possiable off the ground. This will pull the nose to the left when turning left. Also doing the oposite on right turns and giving more clearance to turn right. This will make the sidecar steer a little in the turns. The higher the better and centered across the width of the bike.
The rear mount should be down low and moved right about to the outer end of the right side passenger footpeg away from the centerline. Setup this way they will have a lot of clearance and feel right while riding.
I have seen and ridden setups as discribed in Canada and they will take your breath away as you go through a corner. They will lean till the bike drags the pavement if you are brave enough to do it. I never was that brave. As I have grown older I have come to the conclusion that pain hurts. I don't need to get broken bones at my age.
If my discription above is not clear I will go into a longer winded explanation but I am not an engineer to tell it in fancy words.
Thanks for the info!
"The forward mount Should be as high as possiable"
With my rig, it will then start to interfere with exhaust headers unless I move the mount really close to the back of front tire..
Is that a good thing?
"rear mount moved right about to the outer end of the right side passenger footpeg"
I wasn't thinking that much out to the right but it can be done.
Then it completely clears my exhaust pipe. Very convenient.
so just like uralsharps found with his, the weight of the car will leverage the bike differently in motion.
so the little bit of offset weight on the "inside" of the bike will be relatively unnoticable? I guess if anything it might help kick the rear wheel out in a right hander, giving you better turning and clearance right.
I could see it maybe pulling the rear to the right on stopping tho?
and it would certainly be a ton easier to mount the rear out from the rear footpeg! no armatures, and better clearance.
very interesting, I'm seeing this project coming back into the realm of achievability... thanks mr 'stash!
'beard
A couple things, "as high as possible" could possibly get too hgh depending on frame design etc... Imagine for a moment forces pushing laterally against the the steering stem. Then imagine the same amount of forces down low just ahead of the floorboads or foot pegs. The the first case would influence the bikes lean angle more so than the second case. It might also hinder or slow the riders controlling inputs as well. In transistioning from a straght line to a turn it seems like the upper portion of the bike will swing laterally more than the lower portion. Now if we connect a heavy weight to this, the sidecar, it must also move just as far just as quickly. But the added mass will slow it down like a sliding weight on a Metronome. Yes, you want the outboard wheel to point into the curve but you don't want the sidecar steering the bike. Must be a tradeoff and compromise situation. Again finding that "sweet spot" is what your after, I believe.
I think the Ural just over 200 lbs plus another 100 lbs worth of K-9. When empty the rear mount has almost no weight while the front has about 80 lbs on it. This is why my moving my front mount off center will help shift the weight. A different rig might have more weight on the rear mount? Keep in mind the farther off center the mount is the more vertical change takes place during the curves. The front of the sidecar now raises on a left hander and it drops when turning to the left. I can feel a SLIGHT steering change as my dog shifts his weight around that I did not notice when the front mount was centered. There is a lot to know.
Roy
I wish I could come up with physics model and simulator or something..
Until then, it's in the realm of trial and error.
My welder is on vacation this week.
Fabrication will start after that hopefully.
Originally written by uralsharps on 8/30/2007 11:15 AM
A couple things, "as high as possible" could possibly get too hgh depending on frame design etc... Imagine for a moment forces pushing laterally against the the steering stem. Then imagine the same amount of forces down low just ahead of the floorboads or foot pegs. The the first case would influence the bikes lean angle more so than the second case. It might also hinder or slow the riders controlling inputs as well. In transistioning from a straght line to a turn it seems like the upper portion of the bike will swing laterally more than the lower portion. Now if we connect a heavy weight to this, the sidecar, it must also move just as far just as quickly. But the added mass will slow it down like a sliding weight on a Metronome. Yes, you want the outboard wheel to point into the curve but you don't want the sidecar steering the bike. Must be a tradeoff and compromise situation. Again finding that "sweet spot" is what your after, I believe.
I think the Ural just over 200 lbs plus another 100 lbs worth of K-9. When empty the rear mount has almost no weight while the front has about 80 lbs on it. This is why my moving my front mount off center will help shift the weight. A different rig might have more weight on the rear mount? Keep in mind the farther off center the mount is the more vertical change takes place during the curves. The front of the sidecar now raises on a left hander and it drops when turning to the left. I can feel a SLIGHT steering change as my dog shifts his weight around that I did not notice when the front mount was centered. There is a lot to know.Roy
I re-read your posts describing the rig behaviors.
I also googled "bicycle physics" and found this in wikipedia.
http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics
A bicycle(motorcycle) by itself is pretty complicated.
And now we have a sidecar mounted not rigidly...
"I'm not sure of all the dynamics involved but on my setup the bike tends to lean slightly to the left causing a slight left hand turn while on a level ground. I believe that with the low mounting points, the lateral forces of the sidecar frame (front pulling out, rear pushing in)together with the bike's steering geometry cause this slight left lean. I found that by scooting my butt and shifting my weight to the right side of the saddle as far as practical the steering would pretty much straighten up."
I cannot think about dynamics yet but above you are talking about steady state (level, straight road at constant speed), correct?
I see that momentum from sidecar drag causes yaw to the right (and this pulls out front mount and pushes in rear mount) but I cannot figure out why that causes the motorcycle to lean left and causes the rig to pull left..
If it were a rigid rig, lean out is added to go the rig straight rather than pulled right.. (or lean out is just for compensating road crown??)
I see your insight and understanding of the behavior comes from actual experience with the rig. That's what I need also. Hard to wait for the fabrication and test ride!
BTW, the wikipedia article talks about instability modes. "High speed wobble" sounds scarely. Have you experienced anything like that? How fast have you ever been with the rig?
Yes. I was refering to a slight left lean and slight left turn while riding on flat and level ground at a constant speed. And as speed is increased this does get worse. At 70 mph it is more noticable than 50 mph. So it must be accociated to drag. In glancing at the bicycle phyics it reminds of my previous post "There is a lot to know". I did notice the model of the bicycle in a slight right hand turn had its front wheel tracking on the right side of the rear wheels track. I suspect that the lateral pull of the front mount and pushing in of the rear mount are then causing my wheels to track just the opposite of this bicycle model. My front wheel track is being forced to the right side of the rear wheel track causing a left turn. And with more drag i.e. traveling up hill, accelerating, or higher speed this gets worse. More weight off-center to the Right side would help counter this. I've got a 40 lb brick of lead I might try mounting to front connector arm just to see how much it changes the natural lean angle. The wobble you describe can be felt from time to time whether on the factory Ural rig, Victory-Ural rig and even my Harley Heritage and Victory when solo riding depending on speed and riding conditions. But mostly from riding too slowly with a loose hold of the handlebars. Some people add a hydraulic damper cylinder to help prevent this but I have not felt it is worth the bother. It is not like you need a death grip on the bars, just having both hands on the grips is enough to dampen the momentary wobble effect. At speed this rig is usually easy to control with just one hand. It could very well be worse on larger rigid rigs, I don't know. The Ural bike comes with a friction adjustment to the steering head to help dampen this effect.
Cross that bridge when you come to it.
Roy
Hello uralsharps,
I posted a new thread in "general" forum area but in case you haven't seen it, I finally completed my leaner rig. Thanks again for your help.
I went out for one hour test ride today.
The same twisties I frequented with BSA rigid rig.
It's almost perfect. Now I can finally relax before the tight blind right hander.
No noticeable pulls left or right during accel/decel/constant speed.
Maybe that 5" off centered rear pivot is the key.
The only minor annoyance is slight steering instability during cornering.
It feels like riding a dirt bike on gravel.
It seems that irregular road surfaces affect sidecar attitude and that is transferred to bike steering through the linkage. Maybe the front pivot point is too close to the front wheel.. It goes away as soon as I put the power, just like the dirt bike ride.
Originally written by skiri251 on 8/29/2007 9:23 AM
Thanks for the explanation.The beemer free leaner site also says:
Can anyone point me to this beemer free leaner site?
Originally written by denny on 10/28/2007 3:23 AM
Originally written by skiri251 on 8/29/2007 9:23 AM
Thanks for the explanation.The beemer free leaner site also says:
Can anyone point me to this beemer free leaner site?
http://www.nowandthen.info/Sidecar%20website/index.htm
O yes I've seen that site. Lots of good food for thought there.
I wrote him on Friday, no response yet, but everyone's weekends are busy.
Thanks for the replies.
Cheers, Denny
