Arnstein
New member
- Location
- Kristiansund, Norway
Techy Stuff and Why
- Thread starter julian
- Start date
Techy Question.
Some interesting facts have just rolled in to my computer.
A few posts ago on my build thread we were discussing where the oil would go in my sump during cornering, slosh from side to side and front to back etc and it was mentioned by Cam that the oil would stay in the middle during cornering due to centripetal/fugal force (whichever you like to call it) Well, this sounds feasible (other than oil slosh due to jolting etc) and I thought about it, but it did not sit well in my mind, as this would sort of indicate that all bikes at the same cornering force would then have to have a similar angle of lean, (maybe my theory was wrong but that is what started my questioning) Obviously centre of gravity height, wheel gyroscopic forces etc etc have a great deal to do with your lean angle, so a bike with less angle but the same cornering force would exert more sideways load on the oil to move it off centre?
I have a contact who works for a living on top level data logging used for the GP bike teams, so asked him for a glimpse of a data logging sheet for a GP bike. Now he could not send me a sheet from a team for obvious reasons but he could send me lots of info. I was not overly surprised to see 1.3G cornering forces were easily seen at many points with peaks of almost 1.6G
This makes me think, obviously the oil in the sump will be moving from side to side on a regular basis then on something quick like a GP bike, but how much on a classic racer with a sticky 130 rear tyre? I don't think it will be an issue for me as the sub sump is quite narrow anyway so I could not do much more to keep it where I want it but it is a very interesting question?
And how does that work in theory? Simple theory that I know would indicate 1G is the max, and even at 1 G the oil should be out of center by my reckoning unless the bike is completely on it's side at 90 degrees.
Answers on a post card please
Some interesting facts have just rolled in to my computer.
A few posts ago on my build thread we were discussing where the oil would go in my sump during cornering, slosh from side to side and front to back etc and it was mentioned by Cam that the oil would stay in the middle during cornering due to centripetal/fugal force (whichever you like to call it) Well, this sounds feasible (other than oil slosh due to jolting etc) and I thought about it, but it did not sit well in my mind, as this would sort of indicate that all bikes at the same cornering force would then have to have a similar angle of lean, (maybe my theory was wrong but that is what started my questioning) Obviously centre of gravity height, wheel gyroscopic forces etc etc have a great deal to do with your lean angle, so a bike with less angle but the same cornering force would exert more sideways load on the oil to move it off centre?
I have a contact who works for a living on top level data logging used for the GP bike teams, so asked him for a glimpse of a data logging sheet for a GP bike. Now he could not send me a sheet from a team for obvious reasons but he could send me lots of info. I was not overly surprised to see 1.3G cornering forces were easily seen at many points with peaks of almost 1.6G
This makes me think, obviously the oil in the sump will be moving from side to side on a regular basis then on something quick like a GP bike, but how much on a classic racer with a sticky 130 rear tyre? I don't think it will be an issue for me as the sub sump is quite narrow anyway so I could not do much more to keep it where I want it but it is a very interesting question?
And how does that work in theory? Simple theory that I know would indicate 1G is the max, and even at 1 G the oil should be out of center by my reckoning unless the bike is completely on it's side at 90 degrees.
Answers on a post card please
Exmoor beast
Hero member
- Location
- Minehead,Somerset, ENGLAND OF COURSE
Wall of death- Honda CB200, runs all day long horizontally with a central fixed pickup.
Honda sponsored a GL1000 Goldwing engined sidecar for the TT- it blew up through oil starvation caused by cornering. I have also seen bikes used extensively for wheelying blow up through oil starvation. We used to fit a simple gate in the sump of Z900 to stop oil rushing away from pickup.
Honda sponsored a GL1000 Goldwing engined sidecar for the TT- it blew up through oil starvation caused by cornering. I have also seen bikes used extensively for wheelying blow up through oil starvation. We used to fit a simple gate in the sump of Z900 to stop oil rushing away from pickup.
Wall of death simplifies things a lot though, as long as the mechanicals are strong enough the G loading can keep increasing without effecting other things, but this is not real world racetrack. Wheelying could also be made to work with a flexible dip tube and appropriate sump.
But these two are much more steady state than a race environment. A sidecar would be like a car as it does not lean much.
Tricky territory here.
J
But these two are much more steady state than a race environment. A sidecar would be like a car as it does not lean much.
Tricky territory here.
J
GregT
Hero member
- Location
- Christchurch NZ
Not to my knowledge. Julian, take a look at the latest model sumps on the top of the line sports 1000's - they've become wedge shaped. Deep and Vee section with the pickups as low in the sump as possible. Part of it is getting the oil as far from the crank as possible, part is cornering clearance.
The two problems that this gives you are 1/ ground clearance - see the occasional sump being wiped off in the IOM. And 2/ if the bike is dropped and is still running, the oil runs away from the pickup. I recently built one good GSXR1000 out of two. One had been dropped at Wanganui and did a rod bearing running on it's side.
The trend has also been to mount the oil pump lower in the engine cases too. Associated with running the oil level further away from the crank.
To a certain extent your sub-sump may give protection and continuity of supply if the bike is dropped.
From experience, the oil pickups on a solo give most problems under violent fore and aft loadings. Acceleration/wheelies and braking/stoppies.
This is where roller cranks come in handy as they'll survive on mist - for at least a short time.
Hi Greg,
I have been looping at a lot of moderns and have seen exactly what you describe. Its very interesting.
I am not overleg worried about mega brake power as my bike should have good braken but Nothing compared to modern bikes. Wheelies are also not on the cards as I can simply tell the rider not to. Other than lifting a wheel from time to time. I will fit a kill switch with a spring cord so the bike should not run for more than a split second if crashed.
The sub sump is well baffled so front to rear surge should be minimal.
I’m very interested though to fin out what the oil will do in a high G corner.
J
I have been looping at a lot of moderns and have seen exactly what you describe. Its very interesting.
I am not overleg worried about mega brake power as my bike should have good braken but Nothing compared to modern bikes. Wheelies are also not on the cards as I can simply tell the rider not to. Other than lifting a wheel from time to time. I will fit a kill switch with a spring cord so the bike should not run for more than a split second if crashed.
The sub sump is well baffled so front to rear surge should be minimal.
I’m very interested though to fin out what the oil will do in a high G corner.
J
GregT
Hero member
- Location
- Christchurch NZ
A tether kill switch is mandatory for street circuits here. The rider stayed within the radius of his tether hence it kept running.
I believe there are switches available which will interrupt past a set angle. Might be worth looking at.
I believe there are switches available which will interrupt past a set angle. Might be worth looking at.
Very much doubt that mercury is actually used. Usually a steel ball rolling along an incline, closing a contact at the extremities.
piet
I did write mercury type. I haven't seen mercury since I broke my last thermometer.
Paul
Dellortoman
Hero member
- Location
- Tasmania, Australia
OK, time for a bit of analysis. Feel free to skip this post if your eyes start to glaze over.
BTW, this all comes out of my head using basic high school level physics and maths. It's probably covered more thoroughly in some obscure motorcycle design textbook, but I don't have access to anyone else's musings on the subject.
There will of course be some lateral forces on the oil in the sump as a bike leans into a corner, but I don't think they'd be particularly significant to the design of the oil pickup. That's why I made the statement in Julian's race bike thread that a swinging oil pickup wasn't necessary. A narrow or V-shaped sump with the pump suction tube at the bottom should be more than adequate to ensure reliable oil scavenging. Actually, thinking about it a bit more, a swinging oil pickup could be a disadvantage if it get's stuck on the wrong side. I reckon it's a complication best avoided.
For a bike not to fall over, the G-force acting on the centre of gravity of the bike/rider combination must be aligned through the contact patches of the tyres on the road. This is true whether going in a straight line or leaning into a corner. Those three points (CG + two tyre contact patches define a plane though which all of the forces (including acceleration and braking) act. Let's call this the force plane. If you get a force outside that plane that's not countered by some other input (like putting a foot down), then things become unstable.
The source of the lateral forces is interesting. It comes from the fact that a bike doesn't pivot on its centreline as it leans. It rolls around the curved profile of the tyre, so the contact patch moves off-centre toward the inside of the turn. That means you have to lean a bit further to keep the CG "above" the contact patch. The wider the tyre, the greater the off-centre effect. A wide tyre has the advantage that it effectively increases cornering clearance as you lean, but it also means you have to lean further than a bike with narrow tyres at the same speed.
Another "off-centre" component is the rider. He can hang off the side of the bike to move the CG towards the inside of the turn, reducing the amount the bike has to lean.
As far as the lateral oil slosh is concerned, whether you're pulling 1.3G or 1.6G doesn't really matter. All you need to know is how far the force plane deviates from the centre plane of the bike. That depends on the tyre width and the height of the CG above the ground. That calculation involves a bit of trigonometry (I'm happy to provide the calculation details if anyone is interested).
The lower the CG, the greater the effect of the contact patch offset, so erring on the side of worst case I'll assume a pretty low CG of 600mm above the ground, and a 160mm wide tyre. At a 45° lean, I figured out that the force plane deviates from the bike centre plane by a bit over 8°. At 60° lean like the MotoGP guys can achieve, the deviation is around 13°. That's the angle that the oil surface will deviate from its normal orientation relative to the bike. It'll actually push the oil towards the inside of the turn.
The above calculation doesn't allow for rider gymnastics. In the real world, the rider will lean into the corner, with the effect of standing the bike up a little. That will move the oil back towards the outside of the corner, offsetting the oil shift calculation above. So it may go back to zero, or somewhere near. How much the two opposing actions counteract each other probably depends on the agility of the rider. But even if the rider stays bolt upright, 13° isn't likely to bother the oil pickup even in a full width sump.
BTW, this all comes out of my head using basic high school level physics and maths. It's probably covered more thoroughly in some obscure motorcycle design textbook, but I don't have access to anyone else's musings on the subject.
There will of course be some lateral forces on the oil in the sump as a bike leans into a corner, but I don't think they'd be particularly significant to the design of the oil pickup. That's why I made the statement in Julian's race bike thread that a swinging oil pickup wasn't necessary. A narrow or V-shaped sump with the pump suction tube at the bottom should be more than adequate to ensure reliable oil scavenging. Actually, thinking about it a bit more, a swinging oil pickup could be a disadvantage if it get's stuck on the wrong side. I reckon it's a complication best avoided.
For a bike not to fall over, the G-force acting on the centre of gravity of the bike/rider combination must be aligned through the contact patches of the tyres on the road. This is true whether going in a straight line or leaning into a corner. Those three points (CG + two tyre contact patches define a plane though which all of the forces (including acceleration and braking) act. Let's call this the force plane. If you get a force outside that plane that's not countered by some other input (like putting a foot down), then things become unstable.
The source of the lateral forces is interesting. It comes from the fact that a bike doesn't pivot on its centreline as it leans. It rolls around the curved profile of the tyre, so the contact patch moves off-centre toward the inside of the turn. That means you have to lean a bit further to keep the CG "above" the contact patch. The wider the tyre, the greater the off-centre effect. A wide tyre has the advantage that it effectively increases cornering clearance as you lean, but it also means you have to lean further than a bike with narrow tyres at the same speed.
Another "off-centre" component is the rider. He can hang off the side of the bike to move the CG towards the inside of the turn, reducing the amount the bike has to lean.
As far as the lateral oil slosh is concerned, whether you're pulling 1.3G or 1.6G doesn't really matter. All you need to know is how far the force plane deviates from the centre plane of the bike. That depends on the tyre width and the height of the CG above the ground. That calculation involves a bit of trigonometry (I'm happy to provide the calculation details if anyone is interested).
The lower the CG, the greater the effect of the contact patch offset, so erring on the side of worst case I'll assume a pretty low CG of 600mm above the ground, and a 160mm wide tyre. At a 45° lean, I figured out that the force plane deviates from the bike centre plane by a bit over 8°. At 60° lean like the MotoGP guys can achieve, the deviation is around 13°. That's the angle that the oil surface will deviate from its normal orientation relative to the bike. It'll actually push the oil towards the inside of the turn.
The above calculation doesn't allow for rider gymnastics. In the real world, the rider will lean into the corner, with the effect of standing the bike up a little. That will move the oil back towards the outside of the corner, offsetting the oil shift calculation above. So it may go back to zero, or somewhere near. How much the two opposing actions counteract each other probably depends on the agility of the rider. But even if the rider stays bolt upright, 13° isn't likely to bother the oil pickup even in a full width sump.
GregT
Hero member
- Location
- Christchurch NZ
And the old truism that the shorter the wheelbase, the less lean angle required for a given turn.
A mechanical variable cam timing system?