questions about the rangefinder stalkSubscribe
  1. Member Since
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    Dec 16, 2015, 2:35 PM - questions about the rangefinder stalk #1

    hey guys im building my own Fett can and i have a question. im going to cast all my parts after im done so that i have a nice strong but light helmet.i plan on doing this for the rangefinder stalk as well. but i plan on putting some thin metal tubing in the rangefinder (to run wires for the electronics and to make it strong) i was planning on using aluminum tubing or even thin wall brass but im wondering if all that and the plexiglass on the end will be too much weight for the servo on the inside. obviously another alternative is to use plastic tubing but that sacrifices a little strength. above all my main objective is to have something that i can put IN the mold before casting to maintain the hollow portion for the wires and make sure the thing wont snap when going up and down due to the weight. metal however would alow me to braise it to an axel making the connection to the servo a bit easier and more reliable. or a set screw into a recess in the axel.
    anyway thoughts on this idea??? also if anyone knows any Online stores preferably in the US to purchase such tubing about .125"x.125" without having to order a truck load. but still enough for a small production run.
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  3. Jc27's Avatar
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    Dec 16, 2015, 3:09 PM - Re: questions about the rangefinder stalk #2

    If you get the right servo, weight won't be an issue. Check out servocity.com and look at their servos. They have a formula that calculates the torque of a servo at different lifting lengths
  4. Member Since
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    Dec 16, 2015, 5:24 PM - Re: questions about the rangefinder stalk #3

    Quote Jc27 said: View Post
    If you get the right servo, weight won't be an issue. Check out servocity.com and look at their servos. They have a formula that calculates the torque of a servo at different lifting lengths
    cool. i already have one from a Ex RC plane. will have to see if she works. lol pretty sure its high torque
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    Dec 16, 2015, 5:27 PM - Re: questions about the rangefinder stalk #4

    cant currently find that tool you mention do you know what section its under?
  6. Jc27's Avatar
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    Dec 16, 2015, 6:00 PM - Re: questions about the rangefinder stalk #5

    Select a servo and look for the more info tab about servo strength and speed. It will have the formula in that section.
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    Dec 16, 2015, 6:49 PM - Re: questions about the rangefinder stalk #6

    ahh ok there it is. thank you
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    Dec 17, 2015, 11:50 AM - Re: questions about the rangefinder stalk #7

    ok so i went and dug out my servos i bought a while back.
    heres what i have Spektrum and HiTec
    the spektrum has a torque rating of 46 oz-in (3.3kg-cm) @ 4.8V; 49 oz-in (3.5kg-cm) @ 6.0V
    and the Hitec has a rating of Stall Torque (4.8V): 16.66 oz-in. (1.2kg.cm) Stall Torque (6.0V): 20.83 oz-in. (1.5kg.cm)

    im assumming stall torque means the point at which it stops moving and becomes useless

    a rough measurment of the (unassembled) rangefinder arm is about 8" so heres the thing i want to double check, i come up with .35 lbs of available force (46 oz/16= 2.875/8 [approx. length of the arm]=.359) (using the spektrum as my example) does this mean my rangefinder assembly and stalk can only weigh .35lbs??? (im aware thats a bit actually but im a bit worried about the weight of the perspex and the LED's and the wiring.) and if this might be a cause of consern for you guys do you have any servo reccomendations?
  9. Jc27's Avatar
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    Dec 17, 2015, 11:55 AM - Re: questions about the rangefinder stalk #8

    The servo that I include with my wireless servo kits is the hitec 77BB low profile. I did the calculations and it is plently strong enough for the RF. I used a terminal Fettler kit to get the weight along with one of my wired light kits and the weight of everything was way under the stall torque of that servo.

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