2012 Vetter Challenger Build ( 1981 Yamaha SR185 streamliner)

[bschloop]

offalot, your bike looks amazing. the scale i'm referring to at the scrapyard is the one they weigh your aluminum on, it's usually inside and weighs down to the tenth, and is much more accurate than a bathroom scale. it typically is approximately 4'x4' so you could put your bike up there on its center stand no problem. most bathroom scales only go up to 300lb.and balancing a motorcycle on one would be pretty tough. although you could put it on two separate scales, and add up the axle weights, that would also tell you the weight balance of your bike.

anyway, I just buzzed up the road on my bike minus the windshield, and found a huge difference in and out of tuck. either, the windshield was causing the wobble directly, or it was messing up the aero somehow. but I hit 85 with no wobble, so I'll be leaving the windshield off. might lower the tail lid some too.

[euromodder]

Originally Posted by bschloop

either, the windshield was causing the wobble directly, or it was messing up the aero somehow. but I hit 85 with no wobble, so I'll be leaving the windshield off. might lower the tail lid some too.

It's the air buffeting on your shoulders, causing minute steering inputs.
Even the BMW R1200R with the small optional BMW windscreen suffered badly because of it.

Try a bigger or smaller screen, or try varying the angle (and with it, the point where the air hits your body).
Other solutions are a small spoiler near the top of a windscreen, or leaving a (bigger) gap at the bottom.

[offalot]

Thanks bschloop, Hope I can ride her soon. I have a pallet scale at work so whenever I can take it to work i'll get an accurate reading, till then, bathroom scales it is.

Originally Posted by euromodder

It's the air buffeting on your shoulders, causing minute steering inputs.
Even the BMW R1200R with the small optional BMW windscreen suffered badly because of it.

Try a bigger or smaller screen, or try varying the angle (and with it, the point where the air hits your body).
Other solutions are a small spoiler near the top of a windscreen, or leaving a (bigger) gap at the bottom.

Euromodder, are you saying that it is the wind causing your body to steer the bike erratically? Never thought of that possibility, might be why mine went away when I redesigned the wind screen. I just figured it was turbulence on the front end. So if this theory is correct then you should be able to test it by getting up to 70-80 till you start feeling the buffering, then get into a tuck and it should go away.

[renault_megane_dci]

Originally Posted by offalot

OK got a couple pics of my SR185 project.
A couple months ago:


Crappy cell phone pic from this morning:


I'm probably ready to get a weight as I don't have a whole lot to do to it now, maybe tonight.
These things are light enough to weigh on a bathroom scale, I would think a scrap yard scale that could weigh hundreds of tons wouldn't be accurate down to ~200 lbs.

You teased us too much, where is your own build thread ?

[bschloop]

Euromodder, I don't think it could have been the wind on my shoulders, since there was no wind on my shoulders with the screen, but it could have been the wind on the windscreen, since it's a handlebar mounted windscreen. removing the plexi portion of the windscreen worked to completely get rid of the wobble up to 85mph.

Offalot, I agree you need a build thread for your bike. as much as I love your pics on my thread, and as much as I wish it were my bike, I want to see more about how you did it, and how it turns out. for that you ought to start a thread. by the way, if you're interested in really slick aero for that bike you should check vetter's site for his 1980's high mileage fairing, it's about $1200, but it's designed around the sr185, so it would make an amazing cafe fairing and tail for your bike.

[offalot]

Originally Posted by bschloop

Offalot, I agree you need a build thread for your bike. as much as I love your pics on my thread, and as much as I wish it were my bike, I want to see more about how you did it, and how it turns out. for that you ought to start a thread. by the way, if you're interested in really slick aero for that bike you should check vetter's site for his 1980's high mileage fairing, it's about $1200, but it's designed around the sr185, so it would make an amazing cafe fairing and tail for your bike.

I would, I am just not as diligant as some at documenting everything. I wish I was, I just usually get in the garage get into it and never consider stopping to take pictures and such. I might have enough though to at least make a quick thread profiling what I have done.
As far as the fairing, I may make something like it but $1200 wouldn't go well with this bike. "Project 185" means 2 different things: 1, Obviously the cc of the bike and 2. The budget, and so far I have about $10 to go till I'm at budget, this includes the purchase price of the bike. I'm cheap

[euromodder]

Originally Posted by offalot

Euromodder, are you saying that it is the wind causing your body to steer the bike erratically?

It's one of the possible causes, yes.
When you feel the buffeting on your body, it'll very likely be the cause.

The air sort of collapses into the void left by the windscreen when it moves through the air, and this doesn't happen neatly symmetrically, creating buffeting (and drag).

As an aside, Craig's fairings were renowned for their low buffeting.
Or should I say ARE, because they are still used today and actively traded by the looks of it

650 hits on ebay ...
One of them for Vetter logos, which should look good on a Vetter competition bike

So if this theory is correct then you should be able to test it by getting up to 70-80 till you start feeling the buffering, then get into a tuck and it should go away.

Give it a try.
You partly fill in the void by tucking in.

[euromodder]

Originally Posted by bschloop

Euromodder, I don't think it could have been the wind on my shoulders, since there was no wind on my shoulders with the screen, but it could have been the wind on the windscreen, since it's a handlebar mounted windscreen. removing the plexi portion of the windscreen worked to completely get rid of the wobble up to 85mph.

With a windscreen on the bars, the effects of the buffeting aft of the screen can cause the wobble all by itself as it's directly connected to the bars ; by inducing minute involuntary rider inputs ; or a combination of both .


Leaving a hole or gap in the lower center of the fairing will also reduce the buffeting. Top and/or side spoilers mounted with a gap also tend to do that.

[offalot]

Originally Posted by euromodder

With a windscreen on the bars, the effects of the buffeting aft of the screen can cause the wobble all by itself as it's directly connected to the bars ; by inducing minute involuntary rider inputs ; or a combination of both .


Leaving a hole or gap in the lower center of the fairing will also reduce the buffeting. Top and/or side spoilers mounted with a gap also tend to do that.

When I started to shake a bit at 80 a few times I would try to tense up my arms, almost like bench pressing my handlebars, it helped a little bit but obviously would fatigue you after a while, plus there is probably some torso movement going on in your scenario.
My old honda scrambler had a steering stabilizer, wonder if this would help in this instance.

[renault_megane_dci]

When my bike starts to wobble, I find it useful to let go the throttle a little and hold the handlebar using only my right hand as I red somewhere that the wobble gets worst when one try to compensate.

But then, it is not tank slappers and my wobbling issue happens when leaning along a fast curve (and my rear tire tends to randomly lose pressure).