Engine Mounting and CG location

[BenB]

I had an idea to tilt the engine forward to lower the cylinder/heads mass. I think if you tilt a sports bike engine forward about 10deg you might be able to lower the CG of the car a little bit.

Does anybody know if there are any negative consequences of doing this? I was thinking it might cause problems with oil pressure or lubrication, but at the same time I know that sports bike riders lean the bikes left and right at pretty severe angles and it does not seem to cause problems.

Please let me know what you think...

[BenB]

I had an idea to tilt the engine forward to lower the cylinder/heads mass. I think if you tilt a sports bike engine forward about 10deg you might be able to lower the CG of the car a little bit.

Does anybody know if there are any negative consequences of doing this? I was thinking it might cause problems with oil pressure or lubrication, but at the same time I know that sports bike riders lean the bikes left and right at pretty severe angles and it does not seem to cause problems.

Please let me know what you think...

[Michael Palaszynski]

sounds simple enough. i'd suggest setting up a test stand for the engine that has the ability to rotate the engine in pitch as well as roll. take measurements and see how they compare to your normal pressures, temperatures, etc...

[RStory]

Remember on a motorcycle anytime you are leaning you are also accelerating in the direction of the lean. I know as a rider you don't feel like you are going to fall off the thing, I haven't thought much about what happens to the fluids.

Although I did accidentally tip my bike over pretty far once while it was stationary, and a bunch of fuel spilled out of the carbs. This did not happen leaning into a corner.

But anyway, that is sideways tipping, we are talking forwards backwards. You might not see any gains depending on where the CG is located and what the bottom of your motor looks like... I notice you are from Corvallis and last time I saw it the bottom of OSU's motor was flat, and mounted about as low as possible... so the only way you would lower the CG is if the CG is forward of the axis you have to tilt the engine about.

[Welfares]

To see a fairly extreme case of this, have a look at the University of Auckland site.

http://www.fsae.co.nz/nav/tech.htm

Its an R6, i'm not sure what year.

[MalcolmG]

As you can see on the link above, our engine was tilted back almost 90 degrees from the standard orientation on our last car. It helps with packaging the driver around the engine, and somewhere we have some figures about how much it lowered the centre of mass (it was a decent amount). We did have to dry sump the engine, obviously, and it did cause a number of other issues. This year we're running the motor slightly more upright, which fixes some of our oiling and drive issues. We haven't measured the change in centre of mass height yet.

I think if you leant it forward more, rather than back, you'd find yourself pushing the driver even further forward, whether or not you consider that to be a bad thing I guess depends on your design goals, however if you end up sitting the driver (eg heaviest part of the car) more upright, then it could easily negate the gains made by rotating the engine.

[BenB]

That answers my question. Somebody did it successfully...thanks!

[BeaverGuy]

Ben,

If you look in the Engine folder for the '05 car there is a folder called Misc it has an outline of the motor with the rough position of the engine CG. I believe Eric Reichow helped measure the location and it was measured by hanging the engine from mounting points. So you might want to take a look at it.

Also, as Robert mentioned, the Oregon State car has the engine placed parallel to the ground with the bottom as either the lowest point or second lowest point of the car. From looking at the sketch of CG location I think you would need to rotate it 30-45 degrees forward before you would get a lower engine CG which certainly leads to an interesting packing exercise.

Good Luck