Tight U-Turns

Come on....own up....who has been doing a slow upright u-turn...caught there grippy boot on the road and almost dropped it?

This is why I like the balls-out, lean and power type u-turn, as long as you keep the power on you'll be fine....all over in a flash....good technique on a busy road cos its so quick and looks super cool! You only fall over if the bike stops rolling....tis one of those unexplainable brainiac type scientific thingies!

Here come the centrifugal warriors and gyroscopic gunners to shoot me down in flames!

I have only one thing to say to you....can you follow me at 1 mph at tickover just using a touch of clutch to either keep or slow momentum....if so then how does your gyrofugal thingy work then...erm then!?

I've never got my pointy to register just 1mph on teh speedo.

Originally Posted by RhythmJunkie

how does your gyrofugal thingy work then...erm then!?

have a look at this

I read the first 24 words and had to stop.

What gyroscopic bits in your engine, they are not all gyrating in the same direction at the same time and there are lots of bits going up and down too!
At 1 or even 2 mph the wheels gyroscopic effect is virtually nil....
.....and seeing as you can do the same trick on a bicycle which has no engine....my ....erm....still stands...erm ok?

I'm off to read the rest of the R'tickle!

That would be a fast bike with a wheel rotating at 100rpm....
....approx' 350mph! Very stable though a'la Busa!

I can see his point but you would have to sit revving the motor at about 6k for the extra stability to be noticeable....I mean....we are talking u-turns and practicality here dudes! One slip of the clutch at 6k on an SV and you could end up doing a u-turn around Pluto!

Originally Posted by RhythmJunkie

I read the first 24 words and had to stop.

What gyroscopic bits in your engine, they are not all gyrating in the same direction at the same time and there are lots of bits going up and down too!
At 1 or even 2 mph the wheels gyroscopic effect is virtually nil....
.....and seeing as you can do the same trick on a bicycle which has no engine....my ....erm....still stands...erm ok?

I'm off to read the rest of the R'tickle!

Gyroscopic forces come from objects rotating. You can ignore anything oscillating or "going up and down" as you put it.

As for "what gyroscopic bits" The main things rotating will be the crankshaft and flywheel and they are rotating in the same direction, as is the clutch and lets say half the gearbox(the other half will be rotating the other way so the net effect of hte gearbox is probably ~0). Still that's quite a lot of mass spinning quite quickly.

Engines do generate gyroscopic forces and they are significant. Watch a car engine being revved, you'll see it move. With some vehicles where the engine is mounted longitudinally you can see the whole car move when the engine is revved.

So the gyroscopic forces from engines can be significant.

As for your U-turn "trick" we're talking about tight turns here. By definition the tightest turn you can pull would be with the bike on full lock. Lets see you throw your bike into a quick full lock turn.

Not sure if it is physciological or Physical, but I find that applying some revs and slipping the clutch helped me do my u-turns. Much better than trying to control it with just going on and off the throttle.!
Probably more stable keeping the engine spinning up around 3 -4 k and slipping clutch than having to rev and clutch and de-rev(is that a word?)
LOL

2mths yes that is cool when they rev a chevy and it twists the whole car it does seem connected to power though cos the best twisters seem to be drag top fuellers! More power more twist.
Its a bit different with a little engine doing a few revs and thats what puzzles me how much is it the gyro effect keeping you upright and how much is it the actual driving grippy force that the engine is applying through the tyre?

Try doing the same u-turn just revving the engine for control and see if it works! I have a funny feeling you'll fall off!

I also wonder how many of you have a broadband connection and have watched the Japanese bike cop doing the u-turns?? He does a lean over u-turn in about 12 feet thats a narrow road. More like a canal tow-path!

As for lots of whirring mass...that still doesn't explain the bicycle u-turn!

Originally Posted by RhythmJunkie

As for lots of whirring mass...that still doesn't explain the bicycle u-turn!

Possibly due to no real weight?

I think you just hit the nail on the head there 'therealvw'.

The amount of mass the motorcycle has means that any movements off-centre are going to be slow because there's a lot of mass to be moved requiring lots of 'energy'. So if you are "practised" at making lots of tiny movements to counter the movement of the bike then you can keep it stable whether its in a straight line or a constant curve! Some people will learn very quickly and others more slowly but I'll bet that that's a major reason behind the phenomenon!
When doing a u-turn you constantly move the steering to alter the centre of gravity to keep the bike upright without having to think about it, its the reason the forks have rake so that this tipping off-centre happens, its how counter-steering works.

When I worked in a foundry, ok my hands were stronger then, but I could push my CBR1000F along the smooth factory floor with one hand holding the pillion grab-rail. I even used to let the bike tip slightly so it steered left through 90 degrees to park it, all with one hand. Not a lot of gyroscopic effect there methinks? Just tiny amounts of left and right wobbles of the steering to keep it going straight using the bikes own mass to keep it upright.

You only have to look at how weird counter-steering is to know that tiny unseen movements of your body can have a very great effect on the actions of the bike.
I think its definately human skill, although gyroscopic voodoo must help a bit.
Its the same skill that enables us to walk and run on the ends of our legs without falling over!

A push bike is very lightweight as 'therealvw' remarked, so its more difficult to use its mass in the same way so you are constantly waggling the steering to keep it going straight.