Radial Engine balance calculator

[Peter Twissell]

Spreadsheet to calculate balance of a radial engine.

Enter values for your engine in column C.
If you select 'corrected' slave rod pin angles, they are calculated automatically.
The first graph shows piston displacements from TDC.
The second shows the motion of the centre of mass of each of the master and slave rods.
The third and fourth show the sum of the mass moments, overlaid with the mass moment of the counterweight.
I've increased the crank angle increments from 1 degree to 5 degrees. It can be a bit slow to update otherwise.

To get the best possible balance, adjust the value 'Counterbalance Mass' to get the value of 'Balance error' as small as possible.
Note that the values in the spreadsheet as saved are for a large (2.3 litre, 120kg) engine, hence the otherwise worrying large balance error.
I know I could have used a goal seek function to minimise tha balance error, but I like to see the effect of manually entered changes.

Feel free to share as you wish.

 

[Steamchick]

Hi Peter,
I think the "Displacements from TDC" graph demonstrates how the pistons with rods mounted onto the Master con-rod vary in stroke compared to the Master rod (Mounted directly on the crank) piston.
I think this is a clear demonstration to help Foketry understand how his 3-bank engine will have 2 banks with longer strokes than the master makes? - If I understand what is really happening here?
Thanks for the technical information - I really appreciate the work in this spreadsheet - it will be studied more! (I call this fun. Do I need locking in a padded room yet?).
K2

 

[Peter Twissell]

Hi k2,
Yes, you understand correctly.
No padded room required.
I did enjoy making the spreadsheet, perhaps I should be in the padded room.

 

[ajoeiam]

Spreadsheet to calculate balance of a radial engine.

Enter values for your engine in column C.
If you select 'corrected' slave rod pin angles, they are calculated automatically.
The first graph shows piston displacements from TDC.
The second shows the motion of the centre of mass of each of the master and slave rods.
The third and fourth show the sum of the mass moments, overlaid with the mass moment of the counterweight.
I've increased the crank angle increments from 1 degree to 5 degrees. It can be a bit slow to update otherwise.

To get the best possible balance, adjust the value 'Counterbalance Mass' to get the value of 'Balance error' as small as possible.
Note that the values in the spreadsheet as saved are for a large (2.3 litre, 120kg) engine, hence the otherwise worrying large balance error.
I know I could have used a goal seek function to minimise tha balance error, but I like to see the effect of manually entered changes.

Feel free to share as you wish.

Thank you very much for sharing!!!!

Well - - - if creating such meant that you should be in a padded room - - - - you might either be sharing or my room is one of the other ones - - - one of the well abused ones. (LOL)