recommend linear actuator for lightweight limb

arduino and the inexpensive high performance motors used in drones have renewed a venerable interest in constructing lightweight "bird legs" of say 1 to 2 foot in length. can you please recommend a suitable technology or product for hobbyist budget. i would like performance capable of running.

muscle and memory wires don't seem to offer suitable responsivity. at current, motors and springs look like the best choice, the linear actuators i can find for sale seem to be very slow and expensive.

Robo-Shop Can or US might have what you are looking for depending on the size of your bird. They are made by Firgelli if I spelled it right. There are several lenghts and different types of controls available I have used the RC controlled ones in my 1/4 scale crane. Your second option would be stiff wire controlled
with micro servos like the ones they use for their wings and flaps on a model airplane.

Good luck on your PROJECT.
Regards Doug

Sounds like a crash course in basic mechanics would be useful if you are not already acquainted - and
probably some model making and experimentation. Research as many existing designs as you can find
and have a play. The various linkages that turns rotation into a walking gait are probably a good starting
place - google "strandbeests" for fun example.

ty, crane sounds fun.

in the 90s i had a fair collection of aluminum pieces and rudimentary starts, music hardware then software took most of my time though.

back then it was crap to do - i remember trying to buy electronic parts in a local store, where some old man decided he didn't like my foreign accent or way of dressing or something and took an hour to assemble my list, taking each component in the back of the shop and probasbly destroying it

the other guys in the store were apologising and had their heads down because this old man was apparently a complete bigot about whatever stigma. really great.

of course, he was more interested in how i looked or sounded than what i wanted to do, and didn't want someone with "my" stigma (whatever that was) having any ability or function. what a load of crap mental garbage previous generations saddled us with. how are we supposed to help the world when it is kicking us in the face.

but yes, i've received recognition in audio for being an innovative genius repeatedly for over a decade. i mean, it's all relative, right, but > a decade of recognition in audio tech is a fair testimony for someone who isn't a puppet there to spend money on.

i've had an acclivity towards this project for decades now, i mean, i don't need to list all the activities that relate to it, like modeling, and all the thoughts i have had,

and like your usual happy self-sourcer, i've had my head up my backside in music tech for so long, i was really surprised to see these 60k motors. i ignored drones for years. i still do not own a smart phone.

last time i shopped, 2.5k was affordable, 12k was about the max i could find listed.

and today, people find so much more to communicate about their products! the concept of being able to use a microprocessor for a project like this is really something. but no collation.

as a newbie in the field,
eg. for quadcopter builds, you have to search and organise your product data yourself.. there's no retailer i've found that lets you compare the characteristics of every motor they sell et c. (apart from amazon if you get lucky).

so every newbie who wants to build their own quadcopter without following a recipe has to do a bunch of legwork identifying which products offer the best function.

i've checked haven't checked robo-shop thanks :slight_smile: it's obviosu robotshop have a really small list of suppliers they are interested in promoting and availing to their customers.

seen firgelli and several other brands with entries in i guess the "faster, miniature linear actuator" field (most of these products look like they're aimed at people customising automobiles) but with the hours i've put into it, i've onyl seen so many videos et c.

most mini linears are like $70 up, lot to slam down for something you've never met.

i was hoping to see some existing projects and deal with other regions of the project that are more interesting to me, but it looks like i have to do the "legwork" haha and put the time in myself, wrapping my own solenoids and seeing if i can elicit better performance, the stats never seem very encouraging.

but we see all kinds of crazy stuff people are doing, but these people never discuss the actuators. i doubt that boston dynamics use hydraulics just because they're the most complicated and expensive. .....b ut what do boston dynamics use??? what would they use, if they had a $250 budget?

in some ways it's soo cool, but in other ways... it's like... nowadays... most people seem to only document by vlogging, understandably convenient. but people nowadays seem to talk reeeeallly slowly why i do not know.. and they always want you to watch them open the box for five minutes and explain how you need a thumb nail to open the box with. basically, i want to build a robot army to wipe out all the people who think i need to have the utility of a thumbnail explained to me for five minutes over and over and over again. you kids are crazy. can't you realise, everybody knows that already? is that part of the video used to exchange secret codes or has psychic applicatios? cool. for god's sakes, never video yourself opening a box. your hands are really fleshy that close up bro.

apart from other pursuits that translate to robotics eg. 3d physics in c for movement and audio, jumping stilts, martial arts, rudimentary metallurgy and previous build experience et al i've spent decades living in the desert observing a lot of running birds eg. roadrunners thinking about exactly this. so, you know, there's a high suitability for task quotient :smiley: i expect this topic often correlates with observing nature.

my current notion, since i have such a low awareness of the performance properties of servomotors, actuators and solenoids, is to compose joints of two primary parts: a spring, and whatever actuator/servo mechanism for rotating the joint to a specific angle. the position of the spring is adjusted by an actuator, which then only needs to hold position well and not move too rapidly, so i think a light motor and bolt style actuator would work for that.

i have a bunch of metal springs left over from my last activity here twenty odd years ago, but i expect there are lighter compounds that perform much better.

if the best i can get doesn't have enough force for a light build that can catch air, then adjusting the actuator mounts with solenoids would give it more push. my expectations are for a build somewhere under four pounds.

the way i see it now, all of that is really the fun of it i suppose, though i consider my objective as beyond the construction of the item.

the part that isn't fun is finding eg. most cost effective performance. :slight_smile:

tbh recent thought has produced a diaspora of design. one thing did occur to me - understand i've coded 3d physics and greatly enjoy proceduralism but am generally nescient regarding the responsivity of mechanisms, that a single legged walker (well, hopper) would be much simpler to develop than a walker with two legs.

apart from a "lemur that bounces off walls" video on youtube i haven't seen any other single legged designs (single wheel yes but that's slightly different). it occurs to me it could look quite eerie.

i mean, especially if you built some kind of foam body for it, you could eg. build the thing to look like a limb hopping along or some ghastly thing.

but i am more interested in the function of a biped :slight_smile:

finally answered my own question by looking for servos on ebay.