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Pushrods or Thread and spring? What to do... Darn Swedes!

#1
Hello! Long time viewer, first time poster.

So after watching David and Josh playing around with the DHL and having an old Mosquito HLG in my garage. I decided that I should buy a DHL. After a little research, I bought a Blaster 3 (Thanks David ;) ). No problems with the build so far and have installed the pushrods but after some thought and a little digging it appears that some like the pushrods while others swear on the spring and string for control surfaces. Are there any drawbacks other than weight?

Thanks in advance.

-David
 

quorneng

Active member
#2
David
Are you assuming the string and spring is heavier? Done appropriately it is stronger and lighter. Which why it is popular to use them on light aircraft!
 
#3
Not at all. I was more or less wondering the pro's and con's of each. I went with the pushrods for now with the notion I can always swap them out at a later date.
Thanks for the reply.
-David
 
#4
This is the first time I've heard of the spring and string method for control surfaces. Sounds interesting if I'm picturing it correctly. A spring forces the surface in one direction and a servo is used to pull in the other via the string, is that right? If so, and I could be wrong, wouldn't that fatigue the servo more than a push rod? The servo would not only be fighting the wind resistance against the surface but also the spring resistance. Just a thought. Like I said first time I've ever heard of it.
 

xuzme720

Dedicated foam bender
Mentor
#5
I was picturing a pull-pull string setup with springs acting like a servo saver...but your described method actually makes more sense. A light spring shouldn't put too much strain on a servo, at least not any more than airflow over the surface would as long as it's light enough.