Figuring weight

[ang5t]

  Hi all, I have a quick question about figuring out weight. I found a reply on someone's post that stated that HDPE was about .96 grams per cm³. With that in mind, would a piece that is 24.4cm (L) * 4 cm (H) * 1.27 cm (W)  weigh 118.99 grams? Or 4.16  Oz if you prefer. Been a while since I had to do any math like that. I'm pretty strapped for $$ so I need to make sure my math is good so I don't waste money on too weak of a servo. Thanks in advance.

[airman00]

yes your math is good

[ang5t]

Ok, thanks airman00. I'm working on an arm. almost done with the design I think. The arm itself wasn't so much the tricky part, but figuring all the weight for servo torque, and designing the gripper.  I'll post the gripper design later on at home (@ work now). Thanks again for all the help guys.

P.S.
also, has anyone ever used Eurgle servos before? I was eBay'ing servos, and came across some for reaaal cheap. I wouldn't think that they would be to good at $1.37 ish for 107 oz-in torque.

[Gertlex]

Just a cautionary note: make sure that you're calculating the torque on the servo by multiplying the weight times the distance from the center of gravity of a given arm piece.

[ang5t]

Yea, I went off of the admin's robot arm torque guide. Found out that I needed more torque. Sooo... I read up on gears here and ended up getting some lego technic worm gear assemlby for the shoulder and elbow joints which should work nicely. I picked those up waay cheap, $3.00 for one, $8.00 for the other on ebay. Just comparing that to the average of $5-$10 for just the worm I have found most places.

P.S. Thanks to the admin and whoever else helped get this site started, it has probably saved me lots of money, help get 'just an idea' to something that is a viable plan, and helped me realize this is something that is doable. You guys rock

[Ro-Bot-X]

Did you get something like this?

[ang5t]

yes, very similar to that, the listing said that it was from a technic set, Some minor aesthetic differences, but pretty much the same looking. Hows the quality on those?