[burpg] Re: Measuring Servo Spline
- From: Alessandro Cesar Dias Gomes Filho <acgfilho@xxxxxx>
- To: burpg@xxxxxxxxxxxxx
- Date: Mon, 18 Aug 2014 19:18:36 -0300
Do you have a macro lens? I mean, it's unnecessary with enough resolution
but it might help.
Also, to do the perspective crop you should find something that you know is
square, e.g. a square, and lay it in the same plane as the spline. Use that
as your orthogonal reference in photoshop. You can use your phone as a
square if you know it has right angles. Ideally you want your orthogonal
reference to be the same thickness as the spline.
On Mon, Aug 18, 2014 at 12:01 PM, Cory Absi <cory.absi@xxxxxxxxx> wrote:
> I will be in Canada until Sunday and the entire week after that I am
> devoting to the MkIIb and rocket team stuff so if nobody does it by next
> Monday I will do it. I have my brothers DSLR and a tripod and photoshop so
> I should be good to go lol.
> -Cory
>
> Sent from my iPhone
>
> On Aug 17, 2014, at 6:36 PM, Armor Harris <armorharris@xxxxxxxxx> wrote:
>
> Yeah you only have to get one tooth of the spline, the diameters, and then
> revolve it. So just get super close up on one tooth
>
> On Sunday, August 17, 2014, Mehmet Akbulut <meak@xxxxxx> wrote:
>
>> Alessandro is right. To get the least amount of skew/distortion,
>> perspective crop will help.
>>
>> Unfortunately there is no data sheet. I'm not in Boston, otherwise I
>> would have done it.
>>
>>
>> On Mon, Aug 18, 2014 at 12:46 AM, Alessandro Cesar Dias Gomes Filho <
>> acgfilho@xxxxxx> wrote:
>>
>>> Do they not have a datasheet?
>>>
>>> Also, whoever does this might want to do a perspective crop on the
>>> picture in Photoshop to make sure it is isometric.
>>>
>>>
>>> On Sun, Aug 17, 2014 at 2:24 AM, Armor Harris <armorharris@xxxxxxxxx>
>>> wrote:
>>>
>>>> Hey guys,
>>>>
>>>> We need someone back at the lab to measure the old e-regulator servo
>>>> spline. Looks something like this
>>>>
>>>> http://www.servocity.com/html/hitec_servo_splines.html#.U_A6QvldV8E
>>>>
>>>>
>>>> I think the best procedure here is to use a high resolution camera
>>>> (read: not an iphone) to take a perfectly 2D picture of the servo spline
>>>> with a pair of micrometers set to a known distance on the same plane as the
>>>> servo spline (calipers probably aren't accurate enough unless they're
>>>> really nice ones).
>>>>
>>>> Then, someone can use imageJ to measure the length in pixels of each
>>>> spline tooth and use the distance between the micrometers in the same plane
>>>> as a pixel to length ratio. ImageJ makes it really easy.
>>>>
>>>> I've done this before on another application, I used an SLR with a
>>>> stock lens and a tripod and it worked pretty well. The setup was in a
>>>> difficult environment but I was still able to get accuracy of less than
>>>> .001" You can probably do better since it's in a well lit lab environment
>>>> and you can control the photo a lot better. I would suggest is setting up
>>>> the camera for maximum contrast so that when you zoom in, you can still see
>>>> sharp lines.
>>>>
>>>> Once we get that measured, we want to try using wire EDM to machine our
>>>> own attachments for high precision valves like the thrust vector control
>>>> and the throttle valve. This could potentially make our servo driven valves
>>>> a lot more reliable and rugged, so it's a really big deal if we're able to
>>>> do this.
>>>>
>>>> Anyone up for it?
>>>>
>>>> Armor
>>>>
>>>
>>>
>>
>
> --
> Sent from my phone
>
>
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