Building a tricopter--questions concerning the tail servo and balance

Beemerider

New Member
I'm scratch building my tricopter(my first multi-rotor) and I currently have a few questions (more later I'm sure). I read that metal geared, digital servos were recommended so I wound up ordering two-the first is a Tower Pro MG-995--a standard size servo. The second is an EMax ES08D 9g micro. Trying to keep this low budget as I've already spent far too much on this hobby since getting back into it last spring. As a result these were inexpensive servos. I'll be using the KK2.0 board and three 750kv motors. My frame is homemade from some 1/2" sq birch from the local building supply and a couple of pieces of 1/8" lite ply for the center. At this point each of the three legs is about 20" long. My questions have to deal with (1) which of my 2 servos is appropriate? The MG-995--is it too large and heavy? Or is the 9gr servo going to be large enough? Question (2) I'll be home brewing the yaw mechanism from one of several simple designs I've seen--if I use the standard servo do I need to possibly shorten that leg to offset the added weight? I'm familiar with the idea of proper balance with my fixed wing stuff and I assume that is equally as important with these. I guess I figured that the gyros on the KK2 make some up for some differences but I should have it fairly well balanced to begin with? When I compared the two servos side by side I got to wondering if the 9g is large enough. This has taken me entirely too long to complete as I started thinking about this last fall. I guess as I get older I'm getting slower. I'm sure I'll have more questions as I go along. At least now I have all the pieces and parts in front of me.

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matwelli

Member
9 gram will be fine , whats teh weight of the TP MG 995 ? the problem with using the bigger servo, say if it weighs 50 grams and is 18" back from the centre, then you will need an equivalent amount of weight hanging out the front to balance.
If you are running a camera, it could easily weigh enough to be close, then shift your battery position to fine tune.

you want to get your weight distribution to as close to the centre of the three motors as possible, the less compensation the board needs to make, the better.
 

Beemerider

New Member
Thank you Mat--

The 955 weighs 55 grams. So a 7 fold increase. What you've said makes perfect sense to me. I just wasn't certain the 9g servo had enough oomph to push the motor back and forth. I'm sure I'll be experimenting with all the stuff after getting all the motors and esc's mounted. Now I just need to get myself in gear. Thanks again!

Wayne
 

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