[NSRCA-discussion] Metal Servo Arms
John Gayer
jgghome at comcast.net
Fri Aug 31 16:16:21 AKDT 2007
Has anyone used the water soluble Nelson Hobby paint?
How is it for durability and weight?
John
Woodward, Jim wrote:
> http://www.nelsonhobby.com/cnc.html
>
>
>
> See this link too.
>
> Jim W.
>
>
>
>
>
> * From: * nsrca-discussion-bounces at lists.nsrca.org
> [mailto:nsrca-discussion-bounces at lists.nsrca.org] *On Behalf Of *Earl
> Haury
> *Sent:* Friday, August 31, 2007 11:57 AM
> *To:* NSRCA Mailing List
> *Subject:* Re: [NSRCA-discussion] Metal Servo Arms
>
>
>
> The Al arms are quite resistant to twisting - but you're correct that
> the nylon wheel is plenty strong and the Al wheel stronger than either.
>
>
>
> A few years back I tested the strength of the JR 8411 Al spline and
> the equivalent nylon spline coupled to stock & H9 Al arms. The test
> involved making an adaptor to set over a single arm and position an
> inch-lb torque wrench directly over the shaft. An output gear / shaft
> was clamped in a vise and the torque wrench used to measure the "give"
> point and the failure point with different combinations. All exceeded
> the torque rating of the servo.
>
>
>
> Nylon shaft & arm: "Give" @ 320 oz in and failure @ 480 oz in - the
> spline shaft twisted and slipped, arm spline damage (yet there was
> enough binding to retain some control transfer).
>
>
>
> Nylon shaft & Al arm: "Give @ 320 oz in and failure @ 560 oz in -
> shaft spline total failure.
>
>
>
> Al shaft & nylon arm: No "give" point. Crisp failure @ 560 oz in - arm
> spline total failure.
>
>
>
> Al shaft & Al arm: No "give" point, Crisp failure @ 1600 oz in - no
> spline damage, shaft broke below spine.
>
>
>
>
>
> Earl
>
> ----- Original Message -----
>
> * From: * twtaylor <mailto:twtaylor at ftc-i.net>
>
> * To: * 'NSRCA Mailing List'
> <mailto:nsrca-discussion at lists.nsrca.org>
>
> * Sent: * Friday, August 31, 2007 9:09 AM
>
> * Subject: * Re: [NSRCA-discussion] Metal Servo Arms
>
>
>
> Last night I was playing with them, they fit the plastic output
> gear just fine. I was trying to get them on 8411sa's with the
> metal splines. I finally did but they won't go down as far as a
> nylon arm. Using a magnifying glass I could see where the alum arm
> is fully seated internally. Just looks different than with the
> plastic arm, as the arm doesn't cover the entire part of the
> splines at the bottom like the standard arm does. I'm using this
> on elev with the MK bearing fitting. I'm going to replace the
> rudder arm with a H9 as well.
>
>
>
> Tim
>
>
>
>
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> * From: * nsrca-discussion-bounces at lists.nsrca.org [mailto:
> nsrca-discussion-bounces at lists.nsrca.org ] *On Behalf Of
> *vicenterc at comcast.net
> *Sent:* Friday, August 31, 2007 9:57 AM
> *To:* NSRCA Mailing List ; NSRCA Mailing List
> *Subject:* Re: [NSRCA-discussion] Metal Servo Arms
>
>
>
> Earl,
>
>
>
> I wonder if the aluminum single arm will twist more than the round
> nylon wheel in similar loads and conditions. Using MK
> link (which are very close to the plane of the wheel) with round
> nylon wheels has been working very well for me. The reason why
> the nylon wheel is strong is because the structure is closed. Of
> course aluminum wheel would be stronger than nylon wheel.
>
>
>
> --
> Vicente "Vince" Bortone
>
>
>
> -------------- Original message --------------
> From: "Earl Haury" <ejhaury at comcast.net>
>
> The nylon servo arms are quite adequate when used with a
> clevis that applies the force in line with the plane of the
> arm (typical pin clevis). Pushrod ends that bolt to one side
> of the arm move the force off the plane of the arm and thereby
> impart a twisting force to the arm. (DuBro type ball links are
> the extreme.) Add a bunch of vibration to the normal loads and
> the nylon arm may eventually fail - a wheel is a much better
> choice if one uses the nylon accessories. In addition to
> better withstanding the twisting forces of offset linkage, the
> aluminum arm is more substantial for screw mounting the ball /
> ball bearing end.
>
>
>
> Jim is correct regarding the H9 arms on JR servos - there
> seems to be more variation in the spline of the output than
> the spline of the arm. (An arm tight on one servo may fit
> nicely on another.) OTOH, I've found the H9 arms to fit Futaba
> servos consistently well.
>
>
>
> Earl
>
> ----- Original Message -----
>
> * From: * vicenterc at comcast.net
> <mailto:vicenterc at comcast.net>
>
> * To: * NSRCA Mailing List
> <mailto:nsrca-discussion at lists.nsrca.org> ; NSRCA Mailing
> List <mailto:nsrca-discussion at lists.nsrca.org>
>
> * Sent: * Friday, August 31, 2007 7:28 AM
>
> * Subject: * Re: [NSRCA-discussion] Metal Servo Arms
>
>
>
> For pattern I always use the nylon servo arms that comes
> with the JR servos. I am not sure why you need the metal
> servo arms. Usually I use the round one for aileron and
> elevator. For rudder I use the heavy duty arm that JR
> offers (comes in the 8611 servo). I never have problems
> with the nylon servo arms in pattern application.
>
>
>
> Regards,
>
> --
> Vicente "Vince" Bortone
>
>
>
> -------------- Original message --------------
> From: Bob Richards <bob at toprudder.com
> <mailto:bob at toprudder.com>>
>
> I've used the H9 arms and the SWB arms. No comparison,
> I will continue to use the SWB arms.
>
>
>
> Bob R.
>
>
>
> */Kelly Regan <kelly.regan2 at verizon.net>/* wrote:
>
> Not an answer to your question but I find the SWB
> arms much nicer
> since they are split. They use a a 2/56 clamp
> screw and nylon locking
> nut to draw the clamp tight around the spline of
> the servo shaft.
>
> twtaylor wrote:
>>
>> I bought some Hanger 9 alum servo arms and when I
> put them on they are
>> VERY hard to get to pull down on to the servo. Is
>>
> --
>
> ________________________________
> Kelly Regan
> Home Page: www.reganspace.com
> ________________________________
>
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