Wheel Balance
Wheel Balance
(OP)
Guys! I need help...
How can I calculate the static unbalance of a wheel from the cad data?
Thanks!
How can I calculate the static unbalance of a wheel from the cad data?
Thanks!
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RE: Wheel Balance
What imbalance? The valve stem hole?
RE: Wheel Balance
I suspect Fabrico is implying that your CAD model will not show any signifiant out of balance, as it is primarily due to thickness variations away from nominal. Plus the valve hole.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Wheel Balance
Norm
RE: Wheel Balance
e.g.
mass of the part 18.4 kg
C.G. X=57.93mm
Y= 0.227mm
Z=-0.019mm
Geometrical axis is "x", which is going thru the pilot bore.
Radius of C.G.=0.228
Static unblance= 4.19kg-mm
Is this correct?
Now, I want correlate this with a static balancer using a correction radius of 230.00mm, any ideas?
Thanks! Greg
RE: Wheel Balance
Sounds like you either need to re-align point "A" in the machining process, increase the number of surfaces machined, or re-evaluate the casting.
RE: Wheel Balance
RE: Wheel Balance
It's a 3D model, not a physical part. The numbers he has would be from a perfectly nominal wheel if it were cast and machined, so there really isn't much he can do to improve these numbers, unless the wheel is an asymmetric design or he really screwed up while modeling, or his material properties are way off in the CAD software.
Greg,
An 18.4 kg wheel???? Is this an aluminum wheel???? What's the diameter? Has to be over 20 inches and quite beefy, I would think, unless you're analyzing a casting or making a wheel for a large vehicle like an aircraft, dump truck, diesel semi-truck, etc. or your chosen material density is way off base in the CAD software.
Are you making this calculation with the valve hole removed from the model? If so, then remember, the imbalance will be checked with a valve stem installed at the assembly plant (if the wheel is going to an automaker), so either supress the valve hole subtraction or add a valve stem to your part for the sake of accuracy and more "real world" numbers.
We typically just ask for the weight of the valve stem from the customer, then model a sphere with the center of the sphere being at the center of the valve stem (intersect the centerline of the valve hole with either the angled surface on the tire side of the rim where the valve is drilled OR the spotface on the tire side of the valve). We increase the diameter of the sphere until we reach the same mass as the valve, then unite the sphere with the wheel for the added weight. Optimal conditions would be to have a model of the actual rubber valve stem or tire pressure monitor/valve stem combination. Feel free to email me if you need clarification on the area I'm describing.
This isn't to say our chosen method is perfect or the best way to do it...it just works for us and has resulted in decent quality in terms of predicting physical part balance in a mass production situation.
I hope at least some of this info proves useful. Not enough information on wheels and tires is publicly available and I feel it would greatly improve the industry if we were to share techniques for things like this, including anything related to FEA simulations for rotary fatigue, radial fatigue and impact analysis.
Tim Flater
Senior Designer
Enkei America, Inc.
www.enkei.com
RE: Wheel Balance
Static unblance= 4.19kg-mm
Is this correct?
Now, I want correlate this with a static balancer using a correction radius of 230.00mm, any ideas?
4.19 kg-m = 4.19 g-m = 5.8 oz-in
About 5/8 oz on a 9" radius unless I've done something rather stupid.
17" wheel? Steel?
Norm
RE: Wheel Balance
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Wheel Balance
4.19 kg-mm = 4.19 g-m = 5.8 oz-in
RE: Wheel Balance
Here is my problem, I'm working on a wheel that will be fitted with a presure sensor on the drop-well area, and after the part is fitted with it the balance goes up. So, I'm thinking about a counter-weight at specififed radius.
With the explanation you guys have given me, now I’m confident enough to calculate the counterweight mass.
Thanks!