How to change angle of shooter?

[ksafin]

I saw a similar thread but wasn't seeing the kind of discussion I had in mind.

For changing the angle of a launcher, how would you go about doing it?

Assume point blank that it's a 20" shoot with one or two wheels on one side. Now where do we go?

I'm just lost as to what kind of motor to use, reduction to use, gearbox to use, but most importantly how to even mount the launcher to some kind of pivoting mechanism that utilizes that motor. Just lost. :confused:

[Phyrxes]

One idea is to fix one end as a point of rotation and use a lead screw to adjust the other end.

[Darth Drew]

We're facing the same problem, we were wondering about using a worm gear to drive it with some kind of hinge for the pivot point. (BTW we're not using a turret)

[ksafin]

One idea is to fix one end as a point of rotation and use a lead screw to adjust the other end.

I like this idea.

[KrazyCarl92]

There are several ways to get this type of motion with a motor. One is to use a large gear reduction to generate the amount of torque you need to get the motion you want. Another way is to convert the rotary motion of the motor into linear motion with a lead screw for example, as shown in this video (http://www.youtube.com/watch?v=GdTX1fYzmYM&t=0m58s) for a robotic arm. We used a lead screw with a PG71 gearmotor to adjust the angle of our shooter last year. A rack and pinion type of mechanism may also achieve the motion you are looking for. Many times a counterbalance is applicable to take some of the load off of the motor, increase speed, and/or increase reliability. This could be a type of spring, surgical tubing, gas shocks, or any other way that energy can be stored to counteract gravity or other external forces that the motor will need to overcome to tilt the shooter.

Our team is heavily considering pneumatic actuation as a solution to tilt our shooter because we believe that having a known position without sensor, set point, or mechanical error will be beneficial for consistent shooting, and our strategy does not rely on being able to have a continuously variable shooting angle. A position for starting configuration and another for shooting is enough.

[Spirator]

We know what angles and range we'll need to shoot from so depending on how we decide to play our strategy we'll have a fixed angle or adjustable between two positions using a pneumatic cylinder.

We use pneumatics because they're very good at holding one position and don't need any feedback control.

[G-Hence]

One idea is to fix one end as a point of rotation and use a lead screw to adjust the other end.

This by far is probably the easiest way to change the elevation to a know point. Pneumatic pistons could work but there would be more guessing involve? Anyway, check out throwing machines like baseball pitching machine, football thrower, artillery guns, and even skeet launchers.

[Sparks333]

KrazyCarl92 has a point that I think should be considered regarding pneumatics - one of the trickiest things about any shooting game is trying to come up with a clever way to correlate distance and target elevation with shooter elevation. I highly, highly recommend that teams take their prototypes (or their calculators) and figure out specific angles and shooting speeds that result in a wide range of potential shooting positions - namely, what angle and speed can you set up such that the angle of the shooter changes as little as possible and yet still allow for scoring over much of the field. Then, using pneumatics (or ball screws with limit switches at set locations) pick two or three angles that together will cover all your bases and leave it at that (if you use pneumatics, you might have to do multiple stages or attempt a 3-way valve solution, but much, much easier than a continuous motion solution). It's cool as all get out when you have a system that can automatically track a target in azimuth and elevation, but 9 times out of 10 the system will still be messing around when your window for shooting comes and goes.

Just food for thought.

Sparks

[Peyton Yeung]

We are looking at an arm like shooter in which we run a keyed shaft as a pivot and using sprockets rotate the whole assembly

[kingbrandon14]

http://img.directindustry.com/images_di/photo-g/trapezoidal-leadscrew-nut-4740-2761231.jpg
We are planning to use an igus lead screw (picture above) attached to a strong motor to move the front end of the shooter up and down. We are still debating whether we should have two of these mechanisms (one on each side), or just one.

Another idea is to use pneumatics, but the disadvantage of that is there are only 2 positions: all the way up, and all the way down.

[Herbblood]

How about just having a belt system with a motor? We're using something based off of this, and with the right motor you should be able to left your shooter around the center of gravity on a pivot point.

[JCharlton]

How about a spring to hold the shooter in the up position, and a winch mechanism to pull it down against the force of the spring? Simple pivoting joint, simple little winch one a motor. Simple is good. We're going lead screw, but it's not simple.

[capnslow]

How about a spring to hold the shooter in the up position, and a winch mechanism to pull it down against the force of the spring? Simple pivoting joint, simple little winch one a motor. Simple is good. We're going lead screw, but it's not simple.
Wow, I really like that idea.

We're using a lead screw, I don't know where we got it but it's 8 threads per inch and we're going to drive it with a cim-u-lator. Seams crazy fast but the testing we've done shows it's not too bad.

[rwkling1]

What we did, is we put a mount that allowed us to adjust the angle, but we did not use a motor for it, we thought that we would decide before the match where we wanted to shoot from (front or back of the pyramid) so then we could by hand change the angle and have the angle fixed for that match

[ksafin]

Well we ended up using a car jack that we motorized with a BAG Motor & VersaPlanetary box.. works pretty well; video here:
http://www.youtube.com/watch?v=GrscTRVY8RU&feature=youtu.be

[dchartley]

Here is a vid of our first test run on the chassis. Frisbee shooter works fine and the elevation adjustment runs off of a jack screw powered by a window motor. Used a couple of basic door hinges so that the angle of the motor and screw can change freely.

Doug

http://youtu.be/fuEmQBhBpnw

[BurkeHalderman]

We're using a single air cylinder mounted on the side of the shooter to switch between being level (loading angle) or shooting angle, probably around 35 degrees. To fine tune the shooting angle we're using a magnet on the cylinder to adjust the stoke length.

A fairly simple solution :)

[Bstep]

We're using a single air cylinder mounted on the side of the shooter to switch between being level (loading angle) or shooting angle, probably around 35 degrees. To fine tune the shooting angle we're using a magnet on the cylinder to adjust the stoke length.

A fairly simple solution :)
Could someone please explain how a magnet can be used to adjust the stroke length of a pneumatic piston?
Thanks

[G Fawkes]

Here is a vid of our first test run on the chassis. Frisbee shooter works fine and the elevation adjustment runs off of a jack screw powered by a window motor. Used a couple of basic door hinges so that the angle of the motor and screw can change freely.
Doug
http://youtu.be/fuEmQBhBpnw

How did you connect the lead screw to the window motor?

[BurkeHalderman]

I believe there are different kinds of switches that can be used to adjust the stroke of an air cylinder. The method that I was referring to uses a sensor that can be adjusted along the body of the air cylinder.

This works because the sensor detects a magnet on the inside of the cylinder, once the rod has extended to the desired position the sensor will send a signal which will limit the stroke to that postion.

More information can be found here :

http://www.bimba.com/products-and-cad/actuators/inch/round-line/non-repairable/original-line-magnetic-reed-switch-design/?searchRef=yes

[JohnFogarty]

I know for a fact our team is mounting the front end of our shooter on a bar as the pivot point and then the back end will be sitting on a CAM. Which will allow us to change our angle.

[waialua359]

http://img.directindustry.com/images_di/photo-g/trapezoidal-leadscrew-nut-4740-2761231.jpg
We are planning to use an igus lead screw (picture above) attached to a strong motor to move the front end of the shooter up and down. We are still debating whether we should have two of these mechanisms (one on each side), or just one.

Another idea is to use pneumatics, but the disadvantage of that is there are only 2 positions: all the way up, and all the way down.

We have a lead screw being used to adjust our shooter mechanism, which for the most part, is working like a charm. I cant believe the 1st banebot gearbox ratio we chose was the best one.
Initially after the shooter was built, we mounted it to a varying angle extruded aluminum frame to match the height where we designed the shooter to be. From there we determined the optimal angle range of the shooter head. Thus, the decision to design a varying angle shooter using the lead screw was determined.

[2348humanplayer]

I'd suggest a cam. Basically an offset disc to transform rotational to linear motion. It's compact, and works smoothly.

[jasp]

you could use a screw attached to an encoder to change angle. I would only use pneumatic if you are using pneumatics for something else on your robot because they are very heavy.

[dchartley]

How did you connect the lead screw to the window motor?

We took the black plastic splined connector that came with the motor and glued in the jack screw using JB weld. Took some attention to keep the joint symetrical. The window motor seems to be geared just right for this application.

Doug

[G Fawkes]

We took the black plastic splined connector that came with the motor and glued in the jack screw using JB weld. Took some attention to keep the joint symetrical. The window motor seems to be geared just right for this application.

Doug

Thanks for the quick reply.

How do you keep the black connector on the window motor?

[capnslow]

Last year we did something very similar with a window motor. We used a screw through the plastic connector and into the window motor shaft. However, you have to be careful because last year we had continual problem with pulling the metal cover off of the window motor because it's only crimped on and we were pulling with the screw.

[dchartley]

Thanks for the quick reply.

How do you keep the black connector on the window motor?

We use the force of gravity. The shooting platform weighs enough to hold it down. We had thought about using a bungee but that wasn't necessary.

Doug

[jp1247]

Another idea is to use pneumatics, but the disadvantage of that is there are only 2 positions: all the way up, and all the way down.

Not entirely true. I spent last weekend testing the plausibility of pneumatic angling. By using a dual solenoid, and 1 spike controlling it, im able to get infinite variation with no lack of strength.

The solenoids two red leads go to M+ and M- of the spike, the black going into a splice on the ground side of the spike. By setting the the spike to full forward (12 volts on both pins, 0 pot. difference) the cylinder hold position due to equal pressures. I can then simply set the spike to forward or reverse to raise and lower the piston, having it default back to holding. On a 1"" bore bimba piston, i cant move the shaft at all. Flow control valves on the piston allow me to control how fast it moves up and down.

I may link a video if i get the chance on sunday...

[Negative 9]

Well we ended up using a car jack that we motorized with a BAG Motor & VersaPlanetary box.. works pretty well; video here:
http://www.youtube.com/watch?v=GrscTRVY8RU&feature=youtu.be
What did you use to get the motor onto the end of the screw of the car jack?

[Justin Shelley]

A variable shooting angle is a great idea but we decided that it is not entirely necessary because our shooter is pretty accurate within a twenty foot distance. Though i still want a variable angle mechanism for our robot :(

[fsracer]

We used a small dana linear actuator. Replaced the motor with a legal one. The motor had the same mounting and shaft size! we just cut a d drive in the shaft and it bolted right in.

The actuator was rated for 75 lbs max, and had a 12" stroke, as well as auto limit switches built in. It used 3/8 Bolts to mount.

The conversion took about 15 minutes to do.

And maybe if we used 2, and set the shooter with hooks at 31 inches . . .
Good luck and watch the safety!!

BTW, we used 2 pneumatic cylinders in series to get 3 positions. (1 out, 2 out, none out) for steering a past bot.

Mr. S., Mentor team 3137