DART Linear Actuators for the CIM Motor

[techhelpbb]

What's the repeatable accuracy of this actuator in inches?

[BBray_T1296]

Originally Posted by techhelpbb

What's the repeatable accuracy of this actuator in inches?

I would imagine it is the repeatable accuracy of the potentiometer, which depending on the type/implementation, will be a number significantly less than 1.

[Tom Line]

I think a more appropriate question is how much end play is there in each direction under load. I.E., how much backlash does the geartrain have. Of course, if you always put it in compression is isn't that much of an issue.

[Richard Wallace]

Lash in the potentiometer gear mesh will also be a factor in repeatability, with the ones mentioned in the preceding posts. Of course, lash/play in the mechanism powered by this actuator will be (at least) equally important.

Can someone involved in making the demonstration arm shown in the linked video please measure and post the unpowered vertical play at the end of the arm? I think tape measure accuracy would be enough to give us all a good idea of what to expect.

[Dan Richardson]

Originally Posted by cbale2000

How much does it weigh without the CIM motor?

A fully laden 12" Stroke Length, that's including the pot, CIM and limit switches it's 5.8. According to AndyMark the CIM is 2.8lbs so that would put the DART at 3lbs.

[Dan Richardson]

Originally Posted by Richard Wallace

Lash in the potentiometer gear mesh will also be a factor in repeatability, with the ones mentioned in the preceding posts. Of course, lash/play in the mechanism powered by this actuator will be (at least) equally important.

Can someone involved in making the demonstration arm shown in the linked video please measure and post the unpowered vertical play at the end of the arm? I think tape measure accuracy would be enough to give us all a good idea of what to expect.

You are correct, there will be the backlash in the POT gears, pulleys and screw. You also need to take into account the bit rate of the controller as well if being driven by position commands via feedback from the pot.

We will set up a test to measure the unpowered vertical play in that or similar assembly in the coming week.

[Paul Copioli]

Dan,

Cool product and it looks great.

I do have a question: what is the actual pitch, or lead, of the linear actuator itself?

You gave us the gear ratio (that can be changed ... cool) but having the pitch is a crucial piece of information that many users may not realize they need.

mm/rev, in/rev, mm/deg, mm/rev or whatever units suit your fancy would be appreciated.

Thanks,
Paul

[JamesTerm]

Originally Posted by Dan Richardson

The DART Linear Actuators will be introduced at around $380.

Yow!, why so much?... well, let me know if the price comes down... otherwise I think for me personally it will be more benefit to make them from other cheaper parts. I know I can find good deals on lead screws for around 12-15 dollars.

[Monochron]

Originally Posted by JamesTerm

Yow!, why so much?... well, let me know if the price comes down... otherwise I think for me personally it will be more benefit to make them from other cheaper parts. I know I can find good deals on lead screws for around 12-15 dollars.

I'm thinking it is priced there because it is a good combination of power and speed. The two other similar products linked here and here are both a fraction of the speed that the DART is offering. I'm also guessing that the DART is going to be easier (legal?) to modify, thus giving you much better control of efficiency.

[magnets]

It appears that you're using a normal 3/8" ball bearing to take all the thrust loads from the lead screw. How does this bearing hold up to large impacts and high loading? I only ask because our team has seen issues with bearings falling apart due to high thrust loads.

[Tom Line]

Originally Posted by Monochron

I'm thinking it is priced there because it is a good combination of power and speed. The two other similar products linked here and here are both a fraction of the speed that the DART is offering. I'm also guessing that the DART is going to be easier (legal?) to modify, thus giving you much better control of efficiency.

As for modifying, consider that any motor or transmission with a cim shaft output can drive this. If these turn out to be robust (per the question about how the thrust load is handled) then it's pretty neat what you can do with it with COT's components. Utilizing versa planetaries will result in just about any speed you can imagine.

[Dan Richardson]

Originally Posted by Paul Copioli

Dan,

Cool product and it looks great.

I do have a question: what is the actual pitch, or lead, of the linear actuator itself?

You gave us the gear ratio (that can be changed ... cool) but having the pitch is a crucial piece of information that many users may not realize they need.

mm/rev, in/rev, mm/deg, mm/rev or whatever units suit your fancy would be appreciated.

Thanks,
Paul

Thanks for the kind words Paul. The lead screw has a .500" O.D. and a .200" Lead. This information hadn't made it's way to the website but we've since added it and a calculator to help you determine Forces and Speeds for a custom configuration.

Yow!, why so much?... well, let me know if the price comes down... otherwise I think for me personally it will be more benefit to make them from other cheaper parts. I know I can find good deals on lead screws for around 12-15 dollars.

We're dedicated to producing affordable components for all FRC teams and we will continue to look for ways to improve our design and manufacturing processes to help bring the cost down. As Monochron pointed out, this ground up solution will bring a competitive advantage over other comparable linear actuators. Our actuator is also less expensive than many of the other industry alternatives that allow for similar power density.

It appears that you're using a normal 3/8" ball bearing to take all the thrust loads from the lead screw. How does this bearing hold up to large impacts and high loading? I only ask because our team has seen issues with bearings falling apart due to high thrust loads.

We iterated on the design and selection of bearings in the design process and landed on a high load capacity ball bearing that has performed well in testing. We have safely operated the linear at greater than 300lbs with no damage.

That said, with significant constant load increases there will be decreased bearing life and at some point they may need to be replaced. Since we were focused primarily on the CIM at higher speeds and forces less than 250 lbs I'd like to do some work here to determine what kind of load/life combos we could see.

[JamesTerm]

Originally Posted by Dan Richardson

We're dedicated to producing affordable components for all FRC teams and we will continue to look for ways to improve our design and manufacturing processes to help bring the cost down. As Monochron pointed out, this ground up solution will bring a competitive advantage over other comparable linear actuators. Our actuator is also less expensive than many of the other industry alternatives that allow for similar power density.

I guess everyone has different needs ours is affordability probably under 100 dollars and it doesn't need all the bells and whistles offered on the high end product. I'm not sure if there are others that would like to save money, but if there are... perhaps there is a dialed down version... that might not offer as much force, but could be made with cheaper parts for a cheaper price. I plan on having some solution in the near future on a side project I'm working on.

There is another thread of similar nature that you may wish to check out here: http://www.chiefdelphi.com/forums/sh...93#post1397193

[Ty Tremblay]

Any news on when these will be available on AndyMark?

[Dan Richardson]

Originally Posted by Ty Tremblay

Any news on when these will be available on AndyMark?

The pages are up now and being populated with the technical bits. The DARTs should be available late this week/early next week at AM. The quickest way to get updates will be to select "Email Me When Available".

http://www.andymark.com/SearchResults.asp?Search=dart

Thanks,

Dan R.