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Old 07-18-2010, 10:54 AM   #151
larryboy
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Quote:
Originally Posted by AceRph


Everybody but you & me must be out riding.

Seems to be the case, Rog.

Didn't your FJ rig have car tires on it? How'd it ride compared to a skinny tired Ural..not talking power..., less lean out?
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Old 07-18-2010, 09:51 PM   #152
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Sorry for the late reply, Larry,

I didn't set it up but it doesn't look there's much.

Seems okay though. Handles fine & tire wear isn't weird.
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Old 07-19-2010, 11:15 AM   #153
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No problem Roger, I'm used to waiting here in 'hacks'.


That seems to match what I've seen before, car tired rigs have less lean out if any. I really like a rig that will do left hand burnout circles and stay stable, had one like that before, but it didn't like going straight. The Bandit I got from the Red Menace rode nice and straight even around 100 mph, but the right front corner would dig in on left hand burnout donuts.
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Old 07-19-2010, 03:29 PM   #154
claude
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Quote:
Originally Posted by larryboy
No problem Roger, I'm used to waiting here in 'hacks'.


That seems to match what I've seen before, car tired rigs have less lean out if any. I really like a rig that will do left hand burnout circles and stay stable, had one like that before, but it didn't like going straight. The Bandit I got from the Red Menace rode nice and straight even around 100 mph, but the right front corner would dig in on left hand burnout donuts.
Right hand burnouts are more exciting
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Old 07-19-2010, 06:57 PM   #155
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Quote:
Originally Posted by larryboy
No problem Roger, I'm used to waiting here in 'hacks'.


That seems to match what I've seen before, car tired rigs have less lean out if any. I really like a rig that will do left hand burnout circles and stay stable, had one like that before, but it didn't like going straight. The Bandit I got from the Red Menace rode nice and straight even around 100 mph, but the right front corner would dig in on left hand burnout donuts.

Rob, if you were burying the nose on that rig in left turns, you were doing it wrong! Those rigs stay pretty darn flat turning left or right. Don't brake or sling it into the corner to break the rear wheel loose- Ya need to use more throttle and get your ass off the seat and into the corner. Oh, I forgot. You already wrecked that bike

How is that dirt conversion coming along?
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Old 07-20-2010, 09:46 AM   #156
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How is that dirt conversion coming along?

It's in progress: http://www.advrider.com/forums/showthread.php?t=432320 Probably another six months before it's finished.

I'm cooking up a sidecar project for a bike build off type of thing, 30 day build and under 1k. I'm trying to learn everything I can before the secret start date.
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Old 10-27-2010, 02:41 PM   #157
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I've been trying to find the time to read through the posts on this string, because there's some pretty useful thoughts here.

Sorry to drop a spanner into the gears here, but I have some thoughts that don't agree with all that's been said. I know there are folks out there who disagree.

First, most of the calculations and diagrams in the discussions assume an outfit rolls around the motorcycle or sidecar tire patch(es) That's the situation with any static measurement of loads and tipover forces. However, in motion we have other forces to harness, including tire slip and steering.

Imagine a model of a sidecar (USA style with the car on the right, sorry Aussies), with the motorcycle wheels on two scales to the left, and the sidecar wheel on a scale to the right. Attach strings to the two scales. Now, tip the rig up so all the weight is balanced on the two left side scales. It might appear that any additional roll to the left would capsize the rig, and that the only thing holding it from tipping is the weight of the sidecar.

But, give the two strings a yank toward the left. The outfit would suddenly roll right, and the car would come back down. Feel free to try this at home. Note that the rig rolls back down, rather than sliding to the left. That's because the CoM is up high, so the outfit has resistance to sliding sideways (due to it's inertia) that's centered well above the tire CPs.

Whatever the vehicle, all tires have slip angles when the vehicle is turning, and the operator can adjust both the slip angles and steering to affect roll--similar to the demo above with the imaginary model. For instance, that's why using the throttle and brake together (when turning into the car) helps keep the sidecar on the ground.

So, part of the mystery of sidecar handling is that we have forces other than gravity and "centrifugal force" to help control direction and roll.

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Old 10-27-2010, 02:58 PM   #158
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This thread started with Pete Smith's explanation of determining sidecar wheel lead, and I'd like to momentarily go back to that.

Pete's diagrams are slightly hard to comprehend, because he shows the position of the contact patch moving, rather than the steering axis--as if the rig were suspended off the ground. Perhaps I can help you to understand. (or not)

Go out to your outfit for a little experiment. Steer the front wheel left-right, and watch what happens to the front of the motorcycle. You'll notice that the contact patch stays in the same position, while the front wheel--and steering head--shifts in the direction you're steering. IOW, the front of the motorcycle frame moves laterally, not the CP. And since the sidecar wheel is attached (indirectly) to the motorcycle frame, steering the front wheel drags the sidecar wheel sideways. (and also slightly forward and back) Of course, at speed, other things happen.

Now, the rest of the diagrams should make sense. Greater sidecar wheel lead causes more scrubbing in both left or right turns, but better resists tipovers in left handers. Shorter lead causes less tire scrubbing, but provides less support to resist LH tipovers. In right handers, the sidecar tire will also scrub, if it's still on the pavement. But where the sidecar tire gets pressed down when turning away from the car, it gets lighter when turning into the car. And there will be very little scrubbing with the tire off the ground. That's why the Euro outfits get away with long SC wheel lead--they are low and wide, and can be cornered more aggressively, especially with short trail front ends.
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Old 10-27-2010, 03:04 PM   #159
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David Hough wrote:
>>......I've been trying to find the time to read through the posts on this string, because there's some pretty useful thoughts here.

Sorry to drop a spanner into the gears here, but I have some thoughts that don't agree with all that's been said. I know there are folks out there who disagree.<<

David,
Please disregard most of my stuff on roll center variables. It seems as though I was out to lunch in much of it. At least as far as the experiments we did in trying to raise it on a sidecar outfit.
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Old 10-27-2010, 03:09 PM   #160
claude
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Quote:
Originally Posted by pmdave
I've been trying to find the time to read through the posts on this string, because there's some pretty useful thoughts here.

Sorry to drop a spanner into the gears here, but I have some thoughts that don't agree with all that's been said. I know there are folks out there who disagree.

First, most of the calculations and diagrams in the discussions assume an outfit rolls around the motorcycle or sidecar tire patch(es) That's the situation with any static measurement of loads and tipover forces. However, in motion we have other forces to harness, including tire slip and steering.

Imagine a model of a sidecar (USA style with the car on the right, sorry Aussies), with the motorcycle wheels on two scales to the left, and the sidecar wheel on a scale to the right. Attach strings to the two scales. Now, tip the rig up so all the weight is balanced on the two left side scales. It might appear that any additional roll to the left would capsize the rig, and that the only thing holding it from tipping is the weight of the sidecar.

But, give the two strings a yank toward the left. The outfit would suddenly roll right, and the car would come back down. Feel free to try this at home. Note that the rig rolls back down, rather than sliding to the left. That's because the CoM is up high, so the outfit has resistance to sliding sideways (due to it's inertia) that's centered well above the tire CPs.

Whatever the vehicle, all tires have slip angles when the vehicle is turning, and the operator can adjust both the slip angles and steering to affect roll--similar to the demo above with the imaginary model. For instance, that's why using the throttle and brake together (when turning into the car) helps keep the sidecar on the ground.

So, part of the mystery of sidecar handling is that we have forces other than gravity and "centrifugal force" to help control direction and roll.

pmdave
Hurray for that post. Yes, by all means there are variables. So many times it seems like these things are looked over.
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Old 11-24-2010, 09:42 PM   #161
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Dave, Thanks for posting that last reply. I hadn't checked this thread since a little while after I had it posted as it got way off track (no pun intended) and was not being looked at thoroughly be most people. I know my dads drawings can be a little difficult to read for most but I am glad the topic has gotten back to where it was intended to be and that some people actually understand the pictures and the fact that it does work out correctly to give you the best setup possible. (without spending countless trips testing the 'seat of your pants' for feel of the rig). I will check in to this thread more frequently again.

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Old 12-19-2010, 12:22 AM   #162
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Quote:
Originally Posted by larryboy View Post
I've read thru this thread about 6 times now, good stuff.


Somebody mentioned that running car tires reduces or eliminates the need for bike lean out. How true is that? It seems like you'd still need some to deal with road crown?

Also, is there an ideal weight bias per wheel? I'm mostly curious about how to set up a rig with the engine on/as the sidecar.

I run a car tire for two reasons.
One: Mileage. Since the motorcycle is just a power plant in the side car world It makes more sense to have a 'flat' footed tire. I have a spare rim w/ a m/c tire for when the hack is removed. M/C tire gets about 12K +-... Car tire... 40-50K. You do the math.
Two: Traction. Much better in winter riding.

As for lean out? I never considered it. The 'dynamic handling' of a side car rig seem hard to overcome by just changing to a car tire.




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Old 02-09-2011, 06:14 AM   #163
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tires

Just my 2 cents worth....just completed total "darkside" s/c and rear wheel both had car tires....installed c/t on front wheel this week...rig tracks better and hardly any low speed headshake??..........

rear wheel...Comtrac 175x75x16
front wheel..Excelsior 5.00/525x16...(with innertube)
s/c tire ??? x 13inch car tire....
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Old 04-03-2011, 11:31 PM   #164
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Thought that I would add this memo here since it is relevant to those thinking about going to the dark side on a bike with a 15" diameter stock wheel.



I know that some people have managed to get away with it, but I think there have been at least as many who have tried it and either were never brave enough to get the tire to seat due to how much pressure it takes to stretch it onto the oversize rim, got hurt trying, or had the tire blow out some miles down the road due to the overstressed or damaged bead...

Just a good reminder, IMHO...
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Old 04-04-2011, 12:19 AM   #165
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It's time for a Vulcan Thread Meld...

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