Attention Dragstar XVS 125 Owners/Fans/Potential Buyers

[Ttaskmaster]

If you can keep a long, heavy, unwieldy, ungainly cruiser upright and handle it, then weight or ergonomics is clearly not the issue.
If you can get a bottom-heavy object to remain more upright than a heavier top-heavy one, then ergonomics is *blatantly* a factor.
Where did you learn physics again?

Since we've also established that height is not an issue either, what the fuck is exactly the issue?
The issue is that *we* have proven that it is a factor and that you're just countering (or perhaps trolling) with random bollocks.

Cruiser - High weight, low centre of gravity.
FJ1200 - Greater weight, higher centre of gravity.
Your masterful understanding of physics surely comprehends such a basic concept as even us old-age donkey Harley wannabes can easily understand, right?

Oh wait, I know what the issue is, Ttask just wants to be a contrarian so that he can continue to argue with everything I say!
If you stop posting utter opinionated crap and start coming up with actual proof that more people than *just you* concur with, then we might reach an accord.
Until then, fuck yeah - I disagree with you and will challenge you on every point.

Since my 5'0 girlfriend had trouble keeping my 125 drag upright or reaching the pegs (back when it was still a bobber and using the stock pegs), there's some evidence against you.
So she's a weakling and you're not teaching her how to hold the bike up properly... What's your point? Are you sure she's fully inflated?

And yes, I am aware you can fit swept back bars, that opens a whole can of worms about people's different opinion on whether or not doing that is safe.
No, not different bars, retard. The factory standard ones pivot. You just loosen the risers. But you also know this, having ridden the bike, of course...

Sat on my bob, if I rested my legs out over the pegs highway style, my heel would be only just past the peg, and I'm 5'11.

And how does Bob feel about you sitting on him?

I'm 5' 11" also, with a 33" inside leg and I dwarf the 125.
Are you sure you're sat on the rider's seat and not the pillion pad, or do you just have legs like a stoat?

The 650 drag is even longer, and my legs were basically straight out on the pegs, and I've ridden both a bobbed and stock version, so I'm quite happy to declare that one myth busted and bullshit called.
I counter-bust your bullshit and call you a short-legged freak.
Go on, give us your inside leg measurement.

The reality is, a lower bike is actually HARDER to keep upright because there is less leverage,
WHAT???!!!
Do what, now? Seriously? What fucking "reality" do you live in? Did you have to take the red pill to get there?
Utter bollocks again. I can stand directly over the 650 and simply push down on the right bar grip to bring it upright. Take a Honda M50 - Even a 10 year old child can get that upright and it's even lower than a Cruiser.
Fuck your concept of leverage. You were clearly not paying attention in college!

the greater fork rake creates something called "flop" at low speeds and a standstill, where it has a tendency to want to, sometimes rather violently, flop over onto the steering lock one way or another.
In order for the bars to 'flop' on to the steering lock, you have to tilt the bike over in that direction. If you hold the bike upright, the bars stay level... unless your bike is fucked and abused which... oh, wait - yours is!!
If your bars are trying to 'flop' while you're actually riding along (at ANY speed), perhaps you want to try riding upright and with your hands on the bars!!

A taller bike has much greater leverage, so think like a socket wrench, you use a longer handle to create more torque at the socket, in other words, greater length requires less force, therefore it takes less force/effort to keep a tall heavy bike upright than it does to keep a short heavy bike upright.
Errr.... you seem to be drunk, kid... or just blurting out random crap again.
You've forgotten the weight behind the lever and that little thing called gravity, which applies as you're lifting a mass - The weight you're moving with this socket wrench is not at the pivot end, but further up towards the handle. The FJ's greater weight is even further up, so requires greater force to move it.

Here's a quick virtual sketch for you:

Cruiser: -^----------w--O
FJ1200: -^--*W*--------O


^ = Direction of movement
O = Pivot point
W = Weight
*W* = Greater weight

But I suppose that will be the next thing that you'll chose to disagree with, because you're Ttask and that's what you do.
With physics? Never... just your misinterpretation of it.
I thought you were all smart and stuff?

[Noise]

[DirtyDT]

Can I please ask that everyone plays nicely with each other?

Thank you.

[slice]

DT, They are so far past playing nice that it's become a little intriguing, who will give in first I wonder? Or is this destined to go on for weeks and weeks of petty wrangling over who is right and who is wrong, I for one have to occasionally look back at the begining of the thread to remember what it all started with. Someone will eventually get fed up with this and just stop answering, perhaps that would be best. Thank God it's on here and not in person punches would be flying by now.

[jont]

"Are you sure she's fully inflated?" LOL!

I'm 5'9'' and find my Draggie a joy to ride.The only problem I have is pain in my arthritic shoulder,a result of age, rather than physics I suspect!

[RatBob]

Centre of gravity, or more accurately centre of mass, is calculated by using a datum point and using measurements of various weights on that object and their respective distances from that datum point. It is the unique point where the weighted relative position of the distributed mass sums to zero. It is effectively a useless calculation on a vertical mass, so it will only apply to a motorcycle within it's arc of movement. While the bike is upright on the Y axis, the centre of gravity is zero, and the number increases the closer the bike gets to the X axis, and further it gets from the Y axis. The higher the centre of mass, the more quickly that number will climb as it approaches the X axis, and the higher it's number will be when it is on the X axis.

In order to measure the centre of gravity on a motorcycle, you must take the highest point of leverage, which are the handlebars, and the neck. A line can then be drawn between this point on the Y axis, and it's corresponding point on the X axis, to form the hypotenuse. This is expressed as a measurement.

So if cathetus X is 44 inches and Y is 44 inches, the hypotenuse is the square root of the equation X squared + y squared, which gives us 62.2 inches.

Now, let us take the FJ1200, which gives us another set of equal X and Y catheti, this time of 49 inches. This gives a hypotenuse of 69.3 inches.

Since we know that the crankcase is the heaviest component of the bike, we can fairly safely assume that the height of the crankcase will dictate the centre of mass. The ground clearance of the FJ1200 is is 5.5 inches, and the ground clearance of the Honda Shadow is 5.7 inches. Since both motorcycles carry their engine on the frame, this means that the majority of the weight on both motorcycles is carried at roughly 12 inches above ground level.

If we remove 12 inches from both X catheti, on the FJ and the Shadow, this gives us 37 and 32 inches respectively. This means that the hypotenuse of the FJ becomes 61.4 inches, and the Shadow 58.5 inches.

As we can see, even though the FJ is a taller bike, it has roughly the same centre of mass, yet the hypotenuse is greater than that of the Shadow. This means that the Shadow has a higher relative centre than the FJ. The relative centre is actually a more important factor, because it dictates how much effort is required to keep it upright. It works in exactly the same way as a spanner, where a longer spanner requires less force than a shorter one, because center of gravity is a force that you are acting against. The pivot is your nut, and the bike is your spanner, and it moves through an arc of motion on the pivot.

This is why it takes more physical effort to keep an XVS 650 upright than the equivalent weight FJ1200. The only difference is that having both feet flat on the ground allows you to distribute your weight more effectively and gives you a little more purchase on the ground surface.

[Ttaskmaster]

Since we know that the crankcase is the heaviest component of the bike, we can fairly safely assume that the height of the crankcase will dictate the centre of mass.

Why?

Just because the crank case is the heaviest part, does not mean that the other components higher up have no weight to them. For starters, there's a bloody huge fuel tank atop this thing, you know... Add in quad-carbs, four laterally in-line cylinders (rather than just two longitudinal (roughly) in-line ones), battery, upper frame, a blood massive headlight and instrument housing, fairing et al...

NOT safe to assume. I thought you already tried to lecture me on that one!

There is far more weight far higher up, part of which is the 'lever', that is to say the bike structure itself, which is why (as well as being too short to manage) people drop taller bikes more easily than Cruisers and consequently have more trouble lifting them again.

This is why it takes more physical effort to keep an XVS 650 upright than the equivalent weight FJ1200. The only difference is that having both feet flat on the ground allows you to distribute your weight more effectively and gives you a little more purchase on the ground surface.

Then why will you struggle more to pick up an FJ1200 than you will a Cruiser?

Because you will. I guarantee this... to the point I invite you to come try it on my own bikes. Seriously, come pick up my lighter 650 and then try my heavier FJ. See which one wrenches your back.

Hell, bring a Shadow along and do the same. Have however many feet on the ground you like. Video it and post it here. Whatever you want.

Let's see your physics in action!

[RatBob]

Why?

Just because the crank case is the heaviest part, does not mean that the other components higher up have no weight to them. For starters, there's a bloody huge fuel tank atop this thing, you know...

These things have a negligible effect when the majority of the weight is carried at the crankcase level. The additional weight of the heads makes little difference, because the more pistons you add, the more crank you need. If anything, a V-twin with it's shared crankpin arrangement will actually have a lighter crankcase than an inline four, where each rod has it's own crankpin. The effect of the weight higher up will move the centre of mass slightly higher, but not significantly. The weight of the engine is so massive that we're talking about perhaps an inch or two, no more.

Then why will you struggle more to pick up an FJ1200 than you will a Cruiser?

If they are both the same weight, that won't be true. The centre of gravity will be roughly the same, but the height of the FJ will give me a leverage advantage over the shorter cruiser. It will of course always be easier to lift a lighter bike regardless of how tall it is when you compare it to a heavy bike. The point is here that the only thing that is taller on a sports bike is usually the frame, seat, neck, and sometimes the tank is a fraction higher up than it will be on a cruiser. The ground clearance and engine mounting points are often roughly the same.

Now compare that to a 600cc + supermoto, then we really are talking about high centre of gravity on a tall bike with a heavy engine, believe me you do not want to drop one of those.

As for the video, I might actually cover it in a vlog at some point. I'm currently waiting on funds for a gopro.

[Ttaskmaster]

These things have a negligible effect when the majority of the weight is carried at the crankcase level.

Which is my point. On the FJ it is all higher than you seem to think.

The ground clearance is correct, but my engine sits a good few inches higher.

The Shadow's crank sits slightly (0.5-1") below it's axle line. The FJ's sits 3-4" above. Add to that the higher fuel tank, front frame and all the above, you have a lot of weight high up.

If anything, a V-twin with it's shared crankpin arrangement will actually have a lighter crankcase than an inline four, where each rod has it's own crankpin.

Which is what I was saying about my in-line four and the higher, greater weight.

I could tip my cruiser over way past the sidestand angle and still hold it braced against my left knee. If I tried that with the FJ, I'd have a smashed bike and a snapped leg... as I almost discovered when the sidestand bounced back up as I was leaning it over once!

The weight of the engine is so massive that we're talking about perhaps an inch or two, no more.

And now factoring in the further 3-4" mentioned above, plus all the other heavy high-up parts?

If they are both the same weight, that won't be true.

Hold two 5kg weights out to your sides, arms straight at shoulder height and lean sideways.

Now hold the weights down at your arms' lowest point and lean sideways.

Which one is more likely to make you fall over?

The point is here that the only thing that is taller on a sports bike

The FJ is more Tourer than a Sports and certainly not low down like a Blade or anything these days.

usually the frame, seat, neck, and sometimes the tank is a fraction higher up than it will be on a cruiser.

Mine seems to be the odd one out, then?

believe me you do not want to drop one of those.

No, I really I do, but only because they look like they're made of LEGO™!!

As for the video, I might actually cover it in a vlog at some point.

As you've not filled in your profile - How far from Reading are you?

[RatBob]

Which is my point. On the FJ it is all higher than you seem to think.

The ground clearance is correct, but my engine sits a good few inches higher.

The Shadow's crank sits slightly (0.5-1") below it's axle line. The FJ's sits 3-4" above. Add to that the higher fuel tank, front frame and all the above, you have a lot of weight high up.

Doesn't really matter how far it sits above the axle, because they have different wheel rim diameters. What matters is how far the crank is from ground, and they look about the same to me.

A lower bike requires less movement to get the same angle as a tall bike, because it has a wider arc of movement. So you're a lot more likely to accidentally get the cruiser to an angle that you can't save than you are with a taller bike. I could show you the calculations for how much further in inches the FJ would have to lean to get to the same angle as the shadow, but I'm beginning to think that might be a touch pointless at this stage. This discussion has been distracted from the point and been drawn to revolve entirely around your FJ and how much of a lump it is.

The general principal applies, not because I want it to, but because that's just science fact. Maybe some bikes are an exception, but mostly it's true.

And no I'm not going to be giving any location information on the internet, not even to within 100 miles.

[Ttaskmaster]

Doesn't really matter how far it sits above the axle, because they have different wheel rim diameters.

Nope. *Ground clearance* matters nothing - Above the ground, I have my pipes (no belly pan), then my frame, then a bit of a gap, then finally my crank case and engine. Ground clearance means nothing because, as you say - "what matters is how far the crank is from ground".

However, until I bother to go out and actually measure my crank height, it is still something you can calculate. You can find the wheel rim diameters, calculate the axle height and scale map that on to photos, for accurate measurements.

I have a 3XW by the way, so that's a 17" on the front.

A lower bike requires less movement to get the same angle as a tall bike, because it has a wider arc of movement.

Eh??!!

Because the Cruiser has the wider arc?

Assuming you meant the Tall bike has the wider arc (which it does)... Yes, that part is correct. But so what?

The Cruiser centre of gravity could even be heavier than the Tall, but the height of the CoG *and* its relationship to the length of lever (in this case height of the bars) are the main factors.

With that, the Drop-Angle (might as well find a name for it) on the Tall will be smaller than that of the Cruiser, ie it has to tip less.

So you're a lot more likely to accidentally get the cruiser to an angle that you can't save than you are with a taller bike.

But the Drop-Angle will be greater on the Cruiser, so you'd have to lean it very far 'on accident'... further than the Tall bike.

Also, leverage works both ways. Even if your primary CoG is the same value and height, the longer lever on the Tall adds more weight and raises the overall CoG anyway.

Y

H

|

|

W - Tall

|

|

W - Cruiser

|

|

O------------ X

Assuming X is flat ground, Y is an upright lever with H being the handle, O is the pivot, W is the weight/CoG and the angle X to Y is 90º... As the lever tips over that 90º decreases.

The further out past O and toward X the W is, the heavier it will feel at H.

Now, gravity pulls down the Y axis, so the Cruiser may well reach its Drop Angle of, say, 30º over a shorter arc before the Tall bike reaches its own, but at that angle H will also be closer to O than to X. It is the other way around with the Tall, as the Tall will reach it's Drop Angle of 20º with W further out.

Further more, you have an A frame over the top of the lever, formed by your legs as they hold the bike upright. Assuming the same one rider tests all bikes - The taller the bike, the sooner the lever will interfere with the inner apex of his A frame and the sooner his own centre of gravity will be moved away from a sufficient supporting position to keep the bike up. Similarly, the shorter the rider, the sooner the falling bike will shove their leg out from under them, resulting in the bike hitting the deck, with them collapsing arse-first atop it, with legs flailing in the air and all their mates laughing at them.

So, short rider plus tall bike STILL equals embarrassing drop.

I could show you the calculations for how much further in inches the FJ would have to lean to get to the same angle as the shadow, but I'm beginning to think that might be a touch pointless at this stage.

Yeah, because it reaches its own Drop-Angle before the Cruiser does.

This discussion has been distracted from the point and been drawn to revolve entirely around your FJ and how much of a lump it is.

Nothing wrong with that. I'm proud of my lump!

And no I'm not going to be giving any location information on the internet, not even to within 100 miles.

Paranoid much? Guess you'll have to come to me then.

Can you at least let me know whether you'll be needing full accomodation, or just a cup of tea and a biscuit?

[Ttaskmaster]

Can you at least let me know whether you'll be needing full accomodation, or just a cup of tea and a biscuit?

Also, can you bring your 5' 0" girlfriend. I don't have anyone around here short enough and I'd genuinely like to see her ride the FJ with this technique of yours.

[Noise]

Is someone doing the Tasky? ha ha

But im also very interested to see this technique too.

[lallasro]

do you speak about this technique?

or maybe this?

[slice]

There you are, Lallasro has demonstrated LEVERS at work, that should be an end to this in my opinion but I bet it's not !!!!

[Noise]

Yer such a great technique. i think it works