## Flywheel Inertia with chamfer

## Flywheel Inertia with chamfer

(OP)

Hi

I am currently designing a flywheel to replicate the inertia of a true system in a test rig application.

I have designed a basic cylindrical flywheel to achieve the requested value of inertia. The problem is that the machining company have stipulated a chamfer to be added to either side of the outer radius of the flywheel.

Does anyone know what process I should go through to recalculate the flywheel radius accounting for the champfer?

Even point me in the right direction would be great.

Non champfer detail:

Inertia required : 5.87931658 kgm^2

rho, density : 7850kg/m^3

h, depth : 0.1m

r, radius : 0.262775m

m, 170.2896236 kg

Any help or advice would be appreciated.

5a

I am currently designing a flywheel to replicate the inertia of a true system in a test rig application.

I have designed a basic cylindrical flywheel to achieve the requested value of inertia. The problem is that the machining company have stipulated a chamfer to be added to either side of the outer radius of the flywheel.

**It is important that the inertia of the flywheel is as accurate as possible**, I was hoping to find a formula online that allows you to modify the standardised cylinder formula to account for a chamfer. I will be adjusting the value also when the true density of the metal being used has been communicated. the depth (h) is set at 0.1m only the radius will be manipulated.Does anyone know what process I should go through to recalculate the flywheel radius accounting for the champfer?

Even point me in the right direction would be great.

Non champfer detail:

Inertia required : 5.87931658 kgm^2

rho, density : 7850kg/m^3

h, depth : 0.1m

r, radius : 0.262775m

m, 170.2896236 kg

Any help or advice would be appreciated.

5a

## RE: Flywheel Inertia with chamfer

## RE: Flywheel Inertia with chamfer

## RE: Flywheel Inertia with chamfer

The part will indeed require balancing but unfortunately after manufacture we are unable to then increase the radius to compensate for any differences so I need to find a way to calculate the radius incase of an increase. It's the inertia value that is the target value. I hope that made sense?

3DDave, I've had a quick look at that theorem but i'm struggling to find a valid example that will allow me to make the correct calculation for my problem. I will keep looking though.

## RE: Flywheel Inertia with chamfer

3DDave, I also couldn't find a way to apply the parallel axis theorem. Could you elaborate or show an example?

## RE: Flywheel Inertia with chamfer

I will attempt to replicate your working. You said it's a lot to type in but is a picture of the working feasible?

From what you've calculated that certainly does provide a good snapshot into the effect on inertia of the chamfer. In the application I have the 3DOF model I have developed is certainly affected by the 10mm champfer but I agree that the 1mm shows very little effect.

I still hope to replicate your results so that I can make adjustment to the values and make a decision on adjustment of the radius to compensate the inertia loss.

Thanks again

## RE: Flywheel Inertia with chamfer

I've had some experience with dynamic balancing of high speed rotating components, and even though they were 100% machined from bar stock, they still required a surprising amount of material removed to achieve the dynamic balance condition needed.

## RE: Flywheel Inertia with chamfer

Regards

## RE: Flywheel Inertia with chamfer

## RE: Flywheel Inertia with chamfer

No Chamfer - 5.87930122948

1mm x 1mm Chamfer - 5.87840967285 (-0.015%). Increase radius to 0.26279 gives Lxx = 5.87975

10mm x 10mm Chamfer - 5.79314711169 (-1.4%). Increase radius to 0.26374 gives Lxx = 5.87902

Most of those significant digits are useless unless your machinist can hit 10 micron tolerance and your material density is accurate to better than 0.001%.

The only way to get the inertia accurate to the last significant digit in your specification is to machine the flywheel slightly oversize, measure the inertia and remove material itteratively (finishing with fine emery) until the inertia is correct. Then you will need to maintain the flywheel at a constant temperature (+- 0.0001 degree C)

je suis charlie

## RE: Flywheel Inertia with chamfer

If you start by sensibly rounding the numbers you may discover it all becomes negligible.

I spent years making rotating equipment test rigs and we never worried to the extent you seem top consider important and we used to make systems that ran to 200k rpm on a reasonably regular basis.