Large Model Association Forum

Hi guys

I have finally got my retracts working on the nimrod.

Bit early in the project but here goes.

I have managed to slow the retracting up by restricting the exhaust stroke of the valve but I have done the same with the other stroke but once the weight of the retract comes off the lock it flys down.

Is there a way of mechanically slowing it down, a spring?

Any help would be good.

Cheers

Mike

Hi Mike,
There may be some wya to do it with the air side, but I ma not expert in air retracts. However, I do know all about kinetics or movement of stuff .
Springs just make movement more bouncy. Movement is slowed down or 'damped' by use of a restrictor that has resistance that builds up with speed. The faster the thing moves, the higher the force trying to slow it down. This is just the same as a car shock absorber. I have seen one model where the owner added small oil shock absorbers off RC cars. These are fully adjustable.
Regards, Andy

Mike

Apply more restriction to the exhaust side of the down stroke. You will require considerable more restriction to slow down the down stroke due to the weight of the undercarriage and gravity. Just keep increasing the restriction until you get the speed you need. Please do ensure you are using one way restrictors (Festo make some nice one way restrictirs with a knurled wheel on the top that you can easily wind in or out to get the amount of restriction you require) otherwise you will also be restricting the other stroke and this will cause problems.

John