Advice on star roller design

[JayDee2]

My first new pyro project this year is to build a decent star roller. I have been researching on forums and other fireworks related web sites to try and find out what works best, and have been left with three so far unresolved questions. (Putting aside cost of components for the time being).

 

1/ Material of the tub. i.e. Stainless steel or plastic. There seems to be some comments that say that stainless steel is too "slippery" and that the stars or cores slide instead of rotating. Even seen some videos that say use a plastic bucket and rough up the inside each time with sandpaper. Stainless would seem more robust and certainly easier to clean and this is what several "commercial" suppliers offer. But does plastic actually work better for rolling stars?

 

2/ The shape of the bottom of the tub or bucket. Does the shape of the bottom i.e radiused or square make any difference ? Buckets with square bottoms are readily available. Radiused seem to be more limited in choice.

 

3/ Normal rotation, or vibration rotation. I came across a few star roller videos that use a standard sort of rubber friction roller drive from the motor to the tub, but where the small drive roller is offset/eccentric to its shaft so that it vibrates the bucket (the bearings that the bucket rotates on are on a small swing arm to allow it to move up and down a little ). The theory is that this shakes up the stars as they rotate and stops the larger heavier ones from staying all the time on the bottom, allowing a more even coating of material. I don’t know if this is true or not, but it wouldn’t take much more work to build a star roller in this way if there is any benefit.

 

Has anyone tried or compared the above options?

 

 

 

 

[TYRONEEZEKIEL]

This is my experience. Until I used the 5 gallon bucket one which you'll find all over YouTube. It produced perfectly round stars in good sized batches.

 

If you are willing to spend the money up front and have a proper roller, I suggest getting the cement mixer from harbor freight. You will never need a different roller

[bob]

I find that using a bucket with the same OD as a five gallon bucket, but a little shorter is nicer cause you can see what is going on in there easer.

The bigger stars don't actually stay on the bottom during the rolling process. It is the other way around, the big stars float to the top and get bigger still and so float even more, which creates less uniform stars. Did you ever played with Lego when you were a kid? Cause if you have, you probably noticed how the big chunks tend to be at the top of the container and the small pieces at the bottom, it is the exact same thing with rolling stars.

bob

Edited January 6, 2014 by bob

[TYRONEEZEKIEL]

Yes this does happen, which is why you have to be very thorough and careful with how the comp is added. Star screens eliminate this problem completely though. I usually don't have too bad of sizing problems

[LambentPyro]

Mum Pyrotechnics has great star sizing screens. Ned references them on Fireworking, I bought a lot and I am currently waiting to receive them.

 

I have a star roller, but using a drill is not safe. I want to build one instead of buying one because I want to gain some experience. The only problem I have is trying to pick out a motor. I was looking on McMaster, eBay, and a couple other places.

[ivars21]

You can try wiper motor, it is 12v and can be speed regulated, should also have enough power to spin the bucket.

[LambentPyro]

You can try wiper motor, it is 12v and can be speed regulated, should also have enough power to spin the bucket.

Do you have a link to somewhere where I can purchase one?

[Shadowcat1969]

You can try wiper motor, it is 12v and can be speed regulated, should also have enough power to spin the bucket.

That is what I have on both of my small rollers. And it works very well, I simply used a bolt to mount through the center of my bucket for a direct drive roller. You get one at any automotive junkyard, usually for less than $20.

 

I also picked up a computer power supply from an old PC (for free) and modified it with directions you can find on google to be a benchtop 12 V power supply. The one power supply is also enough to run both of my rollers at the same time. Just make sure to use fairly long wires to run from the power supply to the motor, as a way to isolate the power supply, that way you won't ever get any dust into the hot power supply while rolling.

 

I am also working on the cement mixer roller from Fireworking so I can start making larger batches.

[uncrichie]

Do you have a link to somewhere where I can purchase one?

 

LP try here: http://monsterguts.com/index.php?act=viewProd&productId=4 If you search their web sight they also have a compact power supply for this motor.

 

A word of caution, some wiper motors are designed that the body of the motor is exposed to the elements (rain) via their location at the base of the windshield. Reason being is the water from the rain cools the motor. I have no clue how you'd determine that type from one that does not need this type cooling. For our use in a star roller it would be considered continuous duty so there could be an overheating problem.

 

I ran into this with electric window motors. They are meant for intermitant duty and I tried using one in another application for continuous duty and burned it up. Your mileage may vary I just wanted you to be aware of some possible issues. Kurt

Edited January 7, 2014 by uncrichie

[uncrichie]

LP heres the power supply: http://monsterguts.com/index.php?act=viewProd&productId=11

[LambentPyro]

Where is the pulley on that motor?

[Mumbles]

You have to add the pulley yourself. I've found they're easier to find by searching for sheaves instead.

[LambentPyro]

You have to add the pulley yourself. I've found they're easier to find by searching for sheaves instead.

 

Not the pulley, I meant the drive shaft on the motor.

[Arthur]

The motor from an electric wheelchair works superbly, they are designed for continuous duty and varispeed use. A 24V motor run off a 12v psu runs a fair speed for stars.

[uncrichie]

 

Not the pulley, I meant the drive shaft on the motor.

Wiper motors are geared down this is what gives them really nice torque. If you look at the picture again the motor is the left portion. Its attached to the right portion which is the reduction gearing. The shaft so to speak is the center nut you see attached to the arm. You would loosen the nut, remove the arm and use that small shaft for attachment to the roller bowl.

 

LP, go to this page http://monsterguts.com/index.php?act=viewProd&productId=11 at the bottom of the page is a "click" link that shows the motor in operation. It shows the various speeds achievable with the motor at different voltages. You can see there how the disc is attached to the motor/gear assembly. Hope this helps. Kurt

Edited January 7, 2014 by uncrichie

[BAHume]

Recently bought a wiper motor from Monsterguts. It was fairly cheep when I bought it bundled with a power supply and speed controller. I do have a question on the motor itself. Do I need to ground the motor/motor housing. I'm going to make a portable base for it so I'm not sure how to properly ground it. Thanks.

[Bobosan]

That looks like a nice motor. From watching the wiring instructions on Monsterguts, the ground might attach to the motor housing.

 

Did they include wiring instructions with the speed controller?

[BAHume]

They did include the wiring instructions with the kit and it is simple to do and understand. They included everything except the wire nuts. But nothing about a ground wire or grounding the motor itself. The power control is a three prong plug so I know it's grounded. But no ground wire for the motor and no identifiable ground coming off the motor. I know I can attach a ground to one of the mounting bolts on the motor but I not sure how or what to ground it to. Going to go back to the web site and se what they suggest.

[Bobosan]

hmmm...from what you describe, the motor ground is internal and should be included in the 3 prong power control plug.......unless you meant AC power 3 prong plug. It wouldn't run at all if the motor didn't have ground from the speed controller.

 

If you have an ohmmeter available, you can check to see if one of the pins where the motor control cable plugs in is connected to the motor housing. If you find that, then it doesn't need an external ground wire. There are exceptions to this, like when you only have a 2 prong AC power cord instead of 3 prongs.

[MrB]

I've been hand rolling, and using a bucket star roller. I find my self getting uneven starsizes when batches are to large. Yet, larger batches are a lot easier to roll on. So, i've started to look for something, but yet not had much success finding it. A kind of cement mixer shaped bucket / serving bowl that is 40-50cm wide at the widest part, with a round profile, so to speak. not the 45 degree angle transitions you see on cheaper units. Preferably made of steel, the alternatives being plastic & fiberglass. So far, not much luck, and i might end up making it my self by shaping styrofoam, and using it as a "mold" for a fiberglass unit. Eating it away with mechanical means, and acetone after creating the fiberglass unit should be possible. It's just a pain to make the styrofoam ready to use as a former for fiberglass, the epoxi is just as bad, if not worse, at eating the styrofoam then the acetone...

 

Weirdly enough, i know i saw stuff like this a couple of years back, but it seams they have gone out of fashion, and now i cant find any. Used to be available here in Sweden, as large serving bowls, for snacks.

Bottom line is, the shape should be much like the inside of a tyre. This should be able to provide room for larger batches without them layering on top of one and other. Which should take care of uneven growth. I think. It's just an idea i have.

Anyway, the "advice" would be. Go big. Avoid anything that creates a "narrow - deep" working area, since thats where the stars will layer up, and get uneven growth rates. Like regular buckets. They work, but... just don't, unless you have to.

B!

[BAHume]

The three prong plug is actually the ac power supply. I do have an ohmmeter so I'm going to get everything connected in the next couple of days and see what happens. I tried to hand roll my stars but my personality suffers greatly from lack of patience. I did try the dreaded drill star roller using my 18 volt Ryobi but decided to rethink the safety issue and move on to something safer. I do have a cement mixer which I plan on converting into a star roller sometime in the near future. But my hobby already drives my wife crazy so I have to think before doing or I may end up divorced.

[Bobosan]

The three prong plug is actually the ac power supply. I do have an ohmmeter so I'm going to get everything connected in the next couple of days and see what happens.

 

Yep, a continuity check from earth ground on AC plug to motor housing should give you an idea of what you have. Many of the brick style power supplies like laptops use do not have an earth ground line from supply to device. If that is the case, a single wire from motor housing bolt/nut to the cover plate screw at an AC outlet should work.

[Col]

You wont need to ground the motor case if it was designed for automotuive use as its dc not ac. Most brick type power supplies are double insulated, denoted by a "box in a box" symbol on the case which dont need a ground/earth connection/wire.

The earth pin on a double insulated plug in the wall type unit is only there to open the shutter in the wall socket and its typically made of plastic

 

I use the 712rpm driven shaft on mill and throw on a hankook low profile car tyre, (215/35 x 16) it runs about 26rpm, 2.5ft/sec.

Edited February 26, 2014 by Col

[Sparx88]

An ac powered brushless motor like the ones used in those 3 lb ball mills would outlast any dc brushed motor for this. If a DC brushed motor is to be used then having access to the brushes for comm cleaning and brush replacement is important. If money is no object then buy throw away units that can be easily replaced. Wiper motors are good because they are mostly sealed and gear reduction multiplies torque. But they are almost always brushed motors and will, run hot and will need the brushes replaced at some point and the comm cleaned periodically if you plan to use it a lot. And stalling them out even for a second while under load is naughty and mean to a set of soft brushes and a copper comm. Not trying to be a pri** just spreading some heads up.

[Bobosan]

 

LP try here: http://monsterguts.com/index.php?act=viewProd&productId=4 If you search their web sight they also have a compact power supply for this motor.

 

A word of caution, some wiper motors are designed that the body of the motor is exposed to the elements (rain) via their location at the base of the windshield. Reason being is the water from the rain cools the motor. I have no clue how you'd determine that type from one that does not need this type cooling. For our use in a star roller it would be considered continuous duty so there could be an overheating problem.

 

I ran into this with electric window motors. They are meant for intermitant duty and I tried using one in another application for continuous duty and burned it up. Your mileage may vary I just wanted you to be aware of some possible issues. Kurt

 

I also experienced the power window motor overheat problem just testing my roller with no load. They are intermittent duty motors. Currently upgrading the roller with a larger wiper motor and more robust #25 chain drive instead of direct drive.