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How to verify model weight of Motorcycle model in MotionView?

Hi Everyone,

In motorcycle library model, it is having weight of 185 Kg in log file. But when we check the reaction force at front and rear spindle it is around 210 Kg.

Reaction forces are measured at the force marker placed at both axes from instrumental system.

Can anyone explain this behavior or how to confirm model weight?

Please find model in attachment.

InbuiltExampleModel.mdl

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English

MotionView/MotionSolve

v2022.3

Accepted answers

GTT Adam

Hi Adam,

Thank a lot for detailed explanation.

Have tried as you explained but values of reaction are on higher side.

Is this because of version difference?

Would like to ask another question in case you can explain this. In same model if we remove spring and damper from front and rear both places then also total reaction at jack should match the total mass in log file, correct? But after removing spring and damper, total reaction forces around 500N only! Or I missed something here.

Once again thanks for your time.

Hi Savan,

Based on your results, it looks like you may have skipped step 1 in my previous post. You need to change the Vehicle Restraint from Soft to None. I ran the event with the Soft restraint on just now and it produces the same results you are currently displaying.

This will also significantly impact the model with no springs and dampers, as you have pointed out, as you are essentially holding the bike in the air with the soft restraint and there is very little ground reaction occurring.

Hope this helps!

Adam Reid

All comments

GTT Adam

Hi Savan,

To measure the mass of the model in MotionView, you can select the SUM icon next to the BODIES icon. Doing so shows that your model weighs in at 204.096 kg. The value shown in the LOG file pertains to the aggregate mass computed for use within the STATIC simulation only.

CG/Inertia Summary Tool Location:

CG/Inertial Summary Result:

Hope this helps!

Adam Reid

SVS

Hi Savan,

To measure the mass of the model in MotionView, you can select the SUM icon next to the BODIES icon. Doing so shows that your model weighs in at 204.096 kg. The value shown in the LOG file pertains to the aggregate mass computed for use within the STATIC simulation only.

CG/Inertia Summary Tool Location:

CG/Inertial Summary Result:

Hope this helps!

Adam Reid

Hi Adam,

Thanks for responding.

You have correctly said CG summary and total mass in LOG file computed statically. But doubt lies in verifying total mass of the motorcycle in HyperGraph (Post Processing).

Ideally, Total reaction force at front axle and rear axle shall equal to total weight in log file/CG Summary. Observed mismatch between sum of reaction force and total weight from log file.

Is there is any other way to check total reaction force?

GTT Adam

Hi Adam,

Thanks for responding.

You have correctly said CG summary and total mass in LOG file computed statically. But doubt lies in verifying total mass of the motorcycle in HyperGraph (Post Processing).

Ideally, Total reaction force at front axle and rear axle shall equal to total weight in log file/CG Summary. Observed mismatch between sum of reaction force and total weight from log file.

Is there is any other way to check total reaction force?

Hi Savan,

To verify what is shown in the CG/Inertial Summary toll with HyperGraph, you will need to correct your NPOST event as well as what you are plotting.

First, modify your event such that there is no soft or hard constraint on the vehicle body, which will allow it to settle under gravity. Since this is a motorcycle, you will need to add an in-plane constraint between the vehicle body and the ground which acts normal to the XZ plane. This will keep the motorcycle upright and allow you to see the mass of the vehicle only under gravity. By having a constraint on the body, you are adding a third reaction force, which must be removed.

Second, since your event is using the spindle coupling method and not the platform/jack coupling method, the Axle Load measurement will include all masses except the tires. The exclusion of AutoTires will account for a total mass reduction of 17.3 kg (front and rear tire). This is why you are seeing a difference in the LOG file compared to the CG/Inertia Summary Tool. To include the mass of the tires, you must change the event coupling method from spindle to tire.

Lastly, instead of plotting REQ/10000016 Front Axle Load - f2 and REQ/10000017 Rear Axle Load - f2, after making the above changes, please plot Front Tire - SinglePost - Actuator Force Z(70000126) and Rear Tire - SinglePost - Actuator Force Z(70000132). This will plot the force at the ground and thus include all bodies in the system.

As a result, this will give a front tire ground reaction of 897.218 N and a rear tire ground reaction of 1104.87 N. This totals 2002.088 N, or 204.086 N.

Hope this helps!

Adam Reid

SVS

Hi Savan,

To verify what is shown in the CG/Inertial Summary toll with HyperGraph, you will need to correct your NPOST event as well as what you are plotting.

First, modify your event such that there is no soft or hard constraint on the vehicle body, which will allow it to settle under gravity. Since this is a motorcycle, you will need to add an in-plane constraint between the vehicle body and the ground which acts normal to the XZ plane. This will keep the motorcycle upright and allow you to see the mass of the vehicle only under gravity. By having a constraint on the body, you are adding a third reaction force, which must be removed.

Second, since your event is using the spindle coupling method and not the platform/jack coupling method, the Axle Load measurement will include all masses except the tires. The exclusion of AutoTires will account for a total mass reduction of 17.3 kg (front and rear tire). This is why you are seeing a difference in the LOG file compared to the CG/Inertia Summary Tool. To include the mass of the tires, you must change the event coupling method from spindle to tire.

Lastly, instead of plotting REQ/10000016 Front Axle Load - f2 and REQ/10000017 Rear Axle Load - f2, after making the above changes, please plot Front Tire - SinglePost - Actuator Force Z(70000126) and Rear Tire - SinglePost - Actuator Force Z(70000132). This will plot the force at the ground and thus include all bodies in the system.

As a result, this will give a front tire ground reaction of 897.218 N and a rear tire ground reaction of 1104.87 N. This totals 2002.088 N, or 204.086 N.

Hope this helps!

Adam Reid

Hi Adam,

Thank a lot for detailed explanation.

Have tried as you explained but values of reaction are on higher side.

Is this because of version difference?

Would like to ask another question in case you can explain this. In same model if we remove spring and damper from front and rear both places then also total reaction at jack should match the total mass in log file, correct? But after removing spring and damper, total reaction forces around 500N only! Or I missed something here.

Once again thanks for your time.

GTT Adam

Hi Adam,

Thank a lot for detailed explanation.

Have tried as you explained but values of reaction are on higher side.

Is this because of version difference?

Would like to ask another question in case you can explain this. In same model if we remove spring and damper from front and rear both places then also total reaction at jack should match the total mass in log file, correct? But after removing spring and damper, total reaction forces around 500N only! Or I missed something here.

Once again thanks for your time.

Hi Savan,

Hope this helps!

Adam Reid

SVS

Thanks Adam,

Your suggestion worked.