Centre of gravity using g scales
 

Could someone point me to a thread or link which explains the method for balancing a tricycle undercarriage jet. Found a few but they all relate to tail dragged models. Got a rough idea but never done it before and want to be 100% sure. I have no space for a hanging rig so this is my best option.

Regards
Simon

Make yourself two blocks which are the same height as your scales off the ground. Put 2 blocks under any two wheels and scales under third wheel and note weight. Exchange scales and one block and note weight, repeat this for last wheel. Total model weight is weight1 + weight2 + weight3, lets call this Wm.

Measure carefully the distance from where the main wheels and the nose wheel touch the ground, lets call this L1. Measure carefully along the ground the distance forward from where the main wheels touch the ground to the desired CG, lets call this L2.

Now the total moment trying to rotate the model around the main wheels is Wm x L2, and the resisting moment from the nosewheel is weight on it, lets call this Wn times the distance from the mains to the nosewheel, L1. So the model will balance at our desired position when:

Wn= Wm x L2/L1. To be clear, that's Wm times L2 divided by L1.

So now we put the scales under the nosewheel and the blocks under the mains and move everything around until the scales read Wn and the model will be balanced at the correct point. If you need to add weight to the nose to get the correct reading on the scales you should really add the amount to Wm and re-calculate but in practice the additional weight will be small in relations to overall model weight so not really necessary.

Hope this helps,

Malcolm

Template & instructions from Jet Pilots Organization:

http://www.jetpilots.org/weight_bala...20template.xls

http://www.jetpilots.org/weight_bala...structions.pdf

Jerry

Simon,

I have use the spreadsheet and the method described by the PDF that Jerry has posted a link to, to balance my Hunter, 104 and Ultra lightning. It works perfectly.

Geoff.

Thank you for the responses, that was exactly what I was looking for. Spent ages googling last night, but just couldn't find what I know I had seen before.

Got my PST Reaction to maiden at the weekend, now I've seen the method, I'm sure I will have time to get her rigged and checked.

Regards,
Simon