11 replies to this topic

[Ivan S]

I'm working on an automatic air blaster, which works by a three-way ball valve turned by a motor. The concept is pretty simple, the valve rotates from connecting the main tank(not shown) and the firing tank(nipple on the left), to connecting the firing tank and the barrel. I'm currently using a pololu 350rpm, 110oz-in motor and three 18650 efest batteries. But even fully charged the valve's friction slows the motor to 180 rpm, or 3 shots a second. I'd like to raise that to 4 or ideally 5. Does anyone know where I could find a 300-400rpm motor with significantly more torque than 110oz-in? The best I could find after considerable searching is a FIRST cim motor in conjunction with a gearbox, but I'd like to find a smaller, cheaper option that doesn't require assembly of a gearbox, since one of the goals of this build is simplicity. If you know where to find one, or have any other ideas, I'd really appreciate them!

Edited by Ivan S, 05 August 2014 - 01:04 PM.

[Draconis]

Motors from vehicle power window regulators may be what you are after. They are usually worm drive assemblies, and built for high torque. If you want to pay shipping, I'm sure I could scrounge up a couple from the scrap pile here at the shop I work at.

[awsome]

I'm working on an automatic air blaster, which works by a three-way ball valve turned by a motor. The concept is pretty simple, the valve rotates from connecting the main tank(not shown) and the firing tank(nipple on the left), to connecting the firing tank and the barrel. I'm currently using a pololu 350rpm, 110oz-in motor and three 18650 efest batteries. But even fully charged the valve's friction slows the motor to 180 rpm, or 3 shots a second. I'd like to raise that to 4 or ideally 5. Does anyone know where I could find a 300-400rpm motor with significantly more torque than 110oz-in? The best I could find after considerable searching is a FIRST cim motor in conjunction with a gearbox, but I'd like to find a smaller, cheaper option that doesn't require assembly of a gearbox, since one of the goals of this build is simplicity. If you know where to find one, or have any other ideas, I'd really appreciate them!

Well from what I have learned from my rc hobby, I can suggest a couple of em but I am not sure if it will work in your project. Here is a cheap hi-torque one www.rchobbiesoutlet.com/03011-hsp-rc540-engine-motor/ or you can go look for a specific one here http://hobbyhobby.co...ectric-Motors/. I wouldn't recommend a brushless one because they have 3 wires to power it which means you will need an ECS (electronic speed controller) and a receiver to control the ECS so if you don't have the budget go with a brushed motor. Last but not least I would power the motor with a LIPO battery (a 3s would be best). I really hope this helped you.

[Nerf Gra]

Have you tried finding a lower torque valve?

Also. I'm not Captain Slug, but it would seem to me that at some point you are going to be rotating it so fast the the "firing tank" won't have enough time to prime before being closed off again. I have no idea if you are even anywhere close to this or not but it could happen.

Something like this http://www.mcmaster....4373k53/=t5lssd

Edited by Nerf Gra, 05 August 2014 - 09:52 PM.

[KaneTheMediocre]

Robot marketplace has a lot of geared motors, some of which look appropriate for your application. They aren't cheap by nerf standards, but they aren't industrial prices either. Geared motors generally aren't cheap, as they need to have very small, very strong parts to do their job.

http://www.robotmark...ors_geared.html

[Ivan S]

Here is a cheap hi-torque one www.rchobbiesoutlet.com/03011-hsp-rc540-engine-motor/ or you can go look for a specific one here http://hobbyhobby.co...ectric-Motors/.

Robot marketplace has a lot of geared motors, some of which look appropriate for your application. They aren't cheap by nerf standards, but they aren't industrial prices either. Geared motors generally aren't cheap, as they need to have very small, very strong parts to do their job.
http://www.robotmark...ors_geared.html

Thanks for the recommends guys. I'm sure I'll find something now.

Last but not least I would power the motor with a LIPO battery (a 3s would be best). I really hope this helped you.

Efests can discharge up to 7A with good performance, if I use a motor that needs more current I'll switch. Do LIPOs have any other advantages?

Have you tried finding a lower torque valve?

Also. I'm not Captain Slug, but it would seem to me that at some point you are going to be rotating it so fast the the "firing tank" won't have enough time to prime before being closed off again. I have no idea if you are even anywhere close to this or not but it could happen.

Something like this http://www.mcmaster....4373k53/=t5lssd

Thanks for the idea, but unfortunately all the brass 3-way valves I could find have a mid-point where all three pipes are connected, which makes the whole tank dump out the barrel. In order to avoid that, the axis of rotation needs to be inline with the middle pipe, which I've only found in this plastic one.
Outpacing the priming speed may become an issue, but it hasn't been yet and if it does I'll increase pressure to compensate. Using a ball valve instead of more advanced valves like solenoids leads to issues like that, but I couldn't resist the idea of a fully automatic blaster this simple, so I at least wanted to try it.

[Nerf Gra]

And I applaud you're efforts. Its cool to see someone doing something like this.

From what I gathered from the McMaster listing that valve should only be able to be open one way or the other. Hence why it is called a diverting valve. Its designed to move (divert) flow around something. So it should only be able to alow flow in one direction OR the other. I realize that buying a new valve would require you to rework effectively the entire system but IMO at least that's somehow better than just getting a new motor.

Also about the cycle speed. I realized like 2 min after posting that that problem could be countered by turning up the pressure as you said. ::insert standard warnings about PVC airtanks here::

Cool design though can't wait to see more of it.

[awsome]

LIPOS discharge is measured in "C" like 20c. Here is a couple examples:

1000mah or 1amp & 10C is battery capable of giving you 10a. Same 1000mah with a 25C rating is good for 25A
2500mah lipo 20C is 2.5A x 20, its good for 50A.

Otherwise LIPOS last quite some time and is quite consistent but disadvantages come with it such as cost and it needs to be taken good care or else it might "blow up" kinda...
Here is a great place to buy em: www.hobbyking.com/hobbyking/store/__86__85__Batteries_Accessories-Li_Poly_All_brands_.html

[xXhunter47Xx]

Motors from vehicle power window regulators may be what you are after. They are usually worm drive assemblies, and built for high torque. If you want to pay shipping, I'm sure I could scrounge up a couple from the scrap pile here at the shop I work at.

I second this notion. Window motors are very strong, in robotics we used two of them to pull over 100 lbs of spring force back.

[KaneTheMediocre]

So, I have no doubt that you can get a high torque gearmotor that will turn this valve, but within your price range and battery power limits it may not be as fast as you like. Have you considered just giving it a big crank handle? If you used a belt or gear ratio you could get whatever speed you wanted, and I bet you're strong enough that you will have no problem turning this valve with a big crank handle attached to it, even with a 3:1 or 4:1 speed ratio.

[darthskids]

Would a cordless drill work? Pull off the case, replace the trigger with your own switch to run it and wire in a power source.

[Craftsman]

I would further investigate the FIRST motor from AndyMark. They are used to move some pretty big robots, and with the right gearing ratio, it should have enough torque. I know some members on here know a lot about the cims. PBZ and myself are both involved with FIRST robotics, but he is probably much more involved than myself.

You could try looking here for some ideas.