Team 2526 - Propeller Propulsion Prototype.
 

Vid:

http://uk.youtube.com/watch?v=Dbi4zbcp3wE

Tell me if you want some specs. or whatnot.

Re: Team 2526 - Propeller Propulsion Prototype.
 

try a condensor fan from an airconditioner, works great;)

Re: Team 2526 - Propeller Propulsion Prototype.
 

Have you tested to see if it (or 4 of them) can generate enough force to move your robot?

Re: Team 2526 - Propeller Propulsion Prototype.
 

Have you measured the thrust this produces?

Re: Team 2526 - Propeller Propulsion Prototype.
 

If you noticed, those fans remain stationary. Their high pitch allows them to push a lot of air, yet have minimal thrust because of all the stalling. I'm pretty sure it wouldn't be a good idea. We're currently running 12.25 - 3.75 plane props which at meant for maximum thurst.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Can some other team argue that this interferes with their robot's movement? Just curious.

If it has enough thrust to have any effect on your robot, then why not on the robot in front of you?

Anyone?

Re: Team 2526 - Propeller Propulsion Prototype.
 

Not yet, we haven't had time to make a rig to measure it, or obtain a newton meter for that matter =/

Re: Team 2526 - Propeller Propulsion Prototype.
 

If you say that, then perhaps bumping into other robots should be illegal?

Anyone?

=P

Re: Team 2526 - Propeller Propulsion Prototype.
 

Umm that wasn't a hit at your design


It was a serious question.

Re: Team 2526 - Propeller Propulsion Prototype.
 

You probably could argue that it interferes with your robots movement, but IIRC there's no rule that says interfering with another robots movement is illegal. So, arguing that it interferes with you would be irrelevant.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Yeah i know, but i don't see why it would be any different from physical contact such as bumping and throwing balls at each other.

I mean, it is part of our plan to abuse the fact that we might be able to blow balls away from our trailer, but really, nothings stopping any other team from making a fan, right? =)

Re: Team 2526 - Propeller Propulsion Prototype.
 

Wrong tone? Do i sound bitter or sarcastic or something? Sorry XD

Re: Team 2526 - Propeller Propulsion Prototype.
 

I think he's mainly referring to the word "abuse." So in other words yeah... I think it's you're tone. In other news your "sorry" seemed pretty much sarcastic with your XD at the end of it lol.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Just drop it. Its cool.

woot, 1403 post, Cougar Robotics

Re: Team 2526 - Propeller Propulsion Prototype.
 

To return to the original point of the message. Thank you for the demonstration--while you don't have a newton meter avaliabe it is very simple to build something which will have a similar effect. Take a box and suspend it making a pendulum (longer suspension will mean greater accuracy), mount your fan set up on it and let her rip. By measuring the angle off normal created when your fan is turned on and using a simple bathroom scale to measure the mass of the box and your fan set up you will have more than enough accuracy. Here's the math:
Fractional force of gravity pointing in the horizontal direction: Fgx
Force due to gravity: Fg
Angle created by string from normal: theta
Fgx=Fgsin(theta) By inspection
Fprop=Fgsin(theta)

Note that this lets you give a force in Lbs which are much nicer than newtons.

Re: Team 2526 - Propeller Propulsion Prototype.
 

For teams looking into propeller propulsion here are some helpful hints:

Static thrust depends ONLY on prop diameter and RPM, Pitch only impacts power use and top speed. So you will want the largest diameter, lowest pitch prop you can mount, and spin it as fast you can.

Look at the power curve for the motor you have chosen, and select a prop that will run at the peak power point.

To find where a prop might run, here is a link to download a freeware program of great benefit. The page is in German, but the program is in English. The download link is at the top left of the page. The program is called THRUSTHP.

http://www.hoppenbrouwer-home.nl/ika...rusthpv20d.htm

Re: Team 2526 - Propeller Propulsion Prototype.
 

Here is the calculator we used to calculate the maximum thrust and size of engine required:
http://personal.osi.hu/fuzesisz/strc_eng/index.htm

As others have said the pitch of the props have no effect on static thrust, only the maximum speed at which the craft will be traveling it, and the pitch have enormous effect on the engine. To other teams attempting this method of propulsion, use the smallest pitch you can find (12.25x3.75 was the smallest we found). It will provide the same thrust and require less power.

Due to a loose belt during our first test run, we couldn't run the prop up to full speed :( Spinning that blade at 10k rpm according to our calculator (from above) we will get about 6lb of thrust (12lbs total with 2 of them). Is 12 lbs of thrust enough to move the robots?

Our other possibilities for props are using a 28x4 (still havn't found a low pitch prop this big) spinning at much lower speeds to get more thrust. and one more question if anyone knows this, besides requiring more power, is there a reason to use a 2 prop vs a 4prop blade? Using a 4 blade 28x4 prop spinning at 3500 r, according to this calculator (above) would provide nearly 35lbs of thrust

Re: Team 2526 - Propeller Propulsion Prototype.
 

I seem to recall some theoretical math stating the CIMs driving a wheel on the floor could only generate 9 lbs of thrust, so it might be feasible.

Re: Team 2526 - Propeller Propulsion Prototype.
 

A two bladed prop is more efficient than a 4 bladed one. Don't ask me how I know though because it was demonstrated to my R/C flying club one year. If you could make a 1 bladed prop that would be the most efficient.

Please, please, please do not exceed the max. rpm rating for the prop. I've seen blades break and imbed themselves into wooden benches 10 feet away.
These props are not toys and should be treated as you would a circular saw.
I know you will use proper guarding around the prop. If a prop gets knicked THROW IT AWAY!!!

Other than that it looks like it would do the job of moving your bot around. I think the only problem you will see is a slow take off (no pun intended :) )from a dead stop.

BTW I have been flying model airplanes for 30+ years.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Btw, just to clear some stuff up, we plan on having two of these prop and motor systems, hooked up together with like a car driving system. Seeing as how Max power of the CIM motors occur at 2671 RPM, the RPMs on the prop would be 3.5 times that. I'd guess that been the minimum, so the RPMs would range from the max power RPMs(2671) to the free load RPMs (5342), resulting in the prop RPMs ranging from 8348.5 to 18697. But due to imperfections such as friction and air resistance, it's pretty much guaranteed that it won't be spinning nearly as fast as the free load speed.
Oh and final, there will be a steel wire safety housing around each prop. =D

Re: Team 2526 - Propeller Propulsion Prototype.
 

If the coefficient of friction numbers given to us in the manual are correct, then a full weight robot using wheel propulsion will only get 9 lbs of pushing force from the wheels before they slip. If you can get a total of 12 lbs from two propellers you should be able to outrun the other robots on the field.

One neat thing about propeller propulsion is that (unlike using wheels) your pushing force doesn't depend on the weight of your robot. While wheel driven robots will all accelerate at mostly the same rate, you could put those props on a very lightweight robot and move across the field at rediculous speeds!

Cool stuff, I can't wait to see the final robot.

Re: Team 2526 - Propeller Propulsion Prototype.
 

This was the reason we decided to attempt the whole prop idea. Our plan is to keep the robot as light as possible, 80 pounds (including battery) is our goal. That prototype prop weights around 3-4 pounds (haven't actually weighed it).

Re: Team 2526 - Propeller Propulsion Prototype.
 

It would be nice if you can post the gear ratio and also the propeller size and pitch would be nice.


I would have to argue with that;)

Re: Team 2526 - Propeller Propulsion Prototype.
 

the prop is 12.75 x 3.75 (video used a 12x7). and our gear ratio is about 1:3.5 the gear ratio was just an estimate based on how many times we had to spin the prop around to turn the base gear around.

Re: Team 2526 - Propeller Propulsion Prototype.
 

How come you didn't go with a Ducted Fan set up? You can safely turn a fan unit 25,000 - 30,000 :ahh:
Also the fan shroud would be a good safety cage.

Re: Team 2526 - Propeller Propulsion Prototype.
 

One of our early ideas was a leaf blower, but we decided the high air speed exiting the robot would be unsafe. A larger diameter, slower moving blower like the one shown would be better in this respect.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Except have you noticed how ducted fans don't seem to fly away?
That's because they have really big pitches on the blades, making them move a lot of air, but provide very minimal thrust.

Re: Team 2526 - Propeller Propulsion Prototype.
 

I could be wrong here... I may have forgotten all my physics.
Since this is a near ideal surface, Ff = mu * N; the force of friction is how much "pushing force" you have, so it would depend on your weight. However, once you calculate your maximum acceleration, you have to divide out your weight again, so your actual acceleration does not depend on the weight of your robot, only the coefficient of friction and the constant acceleration of gravity.

Also, could you run through the numbers where you got 9 lb of pushing force for a fully weighted robot? Does this include bumpers and batteries, or just the 54 kg? I got slightly different numbers, but I haven't reviewed my physics for quite a while.

Re: Team 2526 - Propeller Propulsion Prototype.
 

You're right that a robot, by itself, would accelerate the same regardless of it's mass. Using Newton's second law and the formula for frictional force we have two equations:

Ff = m * a
Ff = mu * N = mu * m * g

Setting them equal, we get:

m * a = mu * m * g ---> a = mu * g

The masses cancel, showing that the maximum acceleration of the robot depends just on mu and g (which are both the same for everyone)

The difference between driving with wheels and driving via fans is that the fans provide a pushing force that doesn't decrease with mass. So we just have Newtons second law:

F(fan) = m * a ---> a = F(fan) / m

In this case, acceleration does depend on mass. The lighter you make the robot, the faster it can accelerate.

(It's a little more complicated than this because of the added mass of the trailer, but using a fan still allows you to decrease your overall mass but keep the same pushing force)

Re: Team 2526 - Propeller Propulsion Prototype.
 

HAHAHAHA thas right it took me a while to get it...don't mean to spam the thread..so I'll post


I think the amount of thrust you will need to blow a ball away will severly limit you in terms of weight and size unless u plan on just being a defense robot, in which sense it might make sense to go with a fan...is this purely for blowing balls away or for moving?

Re: Team 2526 - Propeller Propulsion Prototype.
 

Your shaft power is first limited by the maximum continuous current. Over 40 amps, the breakers will pop after some period of time. IIRC At 60 amps, they will pop after about 2 seconds. Until they cool down, they will pop - pop - pop if the overload remains.

Your voltage will be something less than 12V, depending on the condition of your battery and the losses in the speed controller and wiring. The reduced voltage will reduce your RPM (and torque at stall) proportionally. 10V plus or minus 1 is probably a reasonable design number.

Maximum power occurs at 1/2 the free load RPM with a torque load equal to half the stall torque. At 11V this would be about 2400 RPM and 158 Oz-In. However, your efficiency is only about 40% at this point so that 60% of your input power is going to heat. At 40 amps continuous and 10 volts your input power is about 400w and at 60% efficiency your output power would be limited to about 240w. Given the load from your 12.75 x 3.75 prop and ignoring drive losses you would have an RPM of about 7500 (2140 at the motor). Static thrust would be about 4.5 lbs.

You will have friction losses in the drive. The best you can do will be about 97%. You will also have inertia in the gears. This will limit how fast you can change the speed of the props.

You might find the FP motors to be a better match, albeit at lower maximum power, because their no load RPM at 12V is 15,600. Assuming these motors are spec'd similar to last year, the load of an 11x3 prop would give you about 3 - 3.5 lbs thrust at 8-9000 RPM with about 30 amps continuous input power. The airflow could keep the motors cool which is important for the smaller motor frames. You would need to be careful about adding a thrust bearing to limit the axial force on the motor shaft because they are probably not designed for axial loads this high.

Remember the trailer mass. You'll be dragging it around.

To hit the theoretical numbers you need to insure that the props don't stall and that the airflow is not turbulent. You also have to consider the airflow into the prop.

You will have to protect from the prop going forward and in other directions as well. This means a full shroud around the prop back some screening in the front. (Those who have seen a model prop spin off will be familiar with the hazard).

I haven't yet seen convincing numbers that thrusters are practical for primary drive with a trailer in tow. But 4 - 8 lbs from a pair of thrusters may add a considerable edge on top of a friction limited drive.

Above all take additional safety precautions, especially during testing. Make sure the front and sides of your test stand are clear and have everyone well back. Discard any prop with the slightest damage.

Re: Team 2526 - Propeller Propulsion Prototype.
 

It's primary purpose is propulsion, any other effects it may have on other bots or the balls are just extra perks ;D

Re: Team 2526 - Propeller Propulsion Prototype.
 

Where do I find these? Link please? =)

We think we might experience problems with the trailer because all of that air power may be pushing directly on it.. and since it's attached to the bot.. it's like pushing off of yourself.

And stalling may be a problem too, that's why we've gotten the smallest possible pitch on our fan.. although it still ideally runs at like 30 mph.


Yeah, we just got the housing off of standard fans from like offices are such. Those will surely do fine.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Re: Team 2526 - Propeller Propulsion Prototype.
 

Now I'm confused. I thought that Fisher Price were the people that made/sold the CIM motors? These are different ones? Are they legal?

~Thanks.

Re: Team 2526 - Propeller Propulsion Prototype.
 

The small fisher price motors are the ones attached (this year) to the powerwheels transmission. There are actually made by Mabuchi if IIRC.

The CIM's are made by China Industrial Motor (IIRC).

The so-called pimp-CIM's from 2007 were also called Fisher Price motors IIRC because they were used in one of their products.

The small FP are great motors but because they are small they can't be operated at high power levels for as long as the CIM's. The internal fan bearings seem to melt after which the cooling is even less. The CIM's are much more rugged.

If you have a lot of air-flow, however, the FP motors should do well. In a drive train, they tend to burn out quickly without elaborate means to keep them cool.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Those don't seem to fit into any one of the categories there. =/

Re: Team 2526 - Propeller Propulsion Prototype.
 

The Fisher Price motors come in the kit; they're the ones that have the huge funky plastic gearbox attached to them.

Re: Team 2526 - Propeller Propulsion Prototype.
 

When people talk about the FP or Fisher-Price motors, they mean the ones that came in the kit of parts, and that are attatched to the funky plastic gearboxes.

\

edit--yeah, like he said!

Re: Team 2526 - Propeller Propulsion Prototype.
 

2009 Kip of Parts, Page 14, PN: 00968-2910. Motor/Gearbox assembly.

This has the -9015 motor. This year it is installed in the gearbox so you have to remove it. (Last year it was separate). The rules as I understand them let you use these motors with or without the gearbox. You can use 2 at most. I also believe that you can use prior year 9015 as spares.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Very cool, 2526. We are considering using prop thrust as well to augment wheel drive. We are in the process of building a test rig and hope to have a test soon with a few variations on theme. Will be interested to share performance data with you once we've done a few tests.

ONE NOTE OF CAUTION: I winced when I saw your video!! Please anchor the test rig to the table with something OTHER THAN A HUMAN C-CLAMP . . . I'd hate to see someone get hurt. Respect those high velocities. :)

Re: Team 2526 - Propeller Propulsion Prototype.
 

But those FP motors are really small then. I don't think that'd be enough power or torque to spin 12.26-in props.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Oh and I did suggest bolting it down. But my dad (the guy holding) was like nah, i'll just hold it, let's not waste drilling holes in wood. XD

Re: Team 2526 - Propeller Propulsion Prototype.
 

Don't let size deceive you, those little FP motors are about as powerful as the CIMs you are using. They spin MUCH faster (15,500 rpm free speed, approx.), and are air cooled so they do not like to stall. Many teams have used them for applications everywhere from driving arms to winches to drivetrains. They are very well suited to your application.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Maybe I'm thinking too fair inside of the box but I don't see any point in this. What advantage would a propeller propulsion system give you in this years game. It seems as if it wouldn't give you much of an advantage and controlling it would be very difficult - more difficult than a robot sliding on the floor. I would put a bit more thought into this before I made the commitment to a propeller propulsion system.

Btw, I forget who said it but, There's no Air on the moon.

Re: Team 2526 - Propeller Propulsion Prototype.
 

The maximum tractive force on the wheels is a little over 9 lbs at mu = 0.06. Surface and wheel conditions will alter this somewhat.

If you can provide additional propulsion from thrusters with performance on the order of 3 to 6 pounds, you can have significantly more propulsive force than other bots.

Thrust can be vectored, and control can come from driven wheels. So yes, maybe you're still inside the box. That being said, there are many difficulties as usual but FIRST teams have a way of overcoming those.

This year may provide more than the usual benefit to teams who do the math, validate with prototyping, and take a little more time designing their bot as long as they leave enough time for driver training and testing which will be even more important this year.

Yes, there's no air on the moon but there's no hydrazine thrusters allowed by the rules. So they offset each other ;)

Re: Team 2526 - Propeller Propulsion Prototype.
 

One of the main disadvantages I see to the propeller system is it operates the best on a light robot, but the lighter a robot is the easier it is pushed around. This is especially important in this years competition.

Re: Team 2526 - Propeller Propulsion Prototype.
 

But i think that propellers should give it pretty good handling if they can be turned quickly enough. Perhaps we would be able to avoid collisions? =D

Re: Team 2526 - Propeller Propulsion Prototype.
 

Enough talk, let's see it driving a robot around! :)

Re: Team 2526 - Propeller Propulsion Prototype.
 

Them*

This is just the prototype, we'll need to fix this up and then.. build a whole new one...after that get them linked and make them rotate. Oh and our chassis still doesn't even have wheels.

So maybe we'll get a video of that by the end of week 2 at best.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Here is one
no power except props


http://www.youtube.com/watch?v=FYdPk6jX2n4&eurl=http://www.youtube.com/my_videos_edit2?ns=1&video_id=FYdPk6jX2n4&next=%2F my_videos2%3Fpi%3D0%26ps%3D20iurl=http://i3.ytimg.com/vi/FYdPk6jX2n4/hqdefault.jpg&feature=player_embedded

http://www.youtube.com/watch?v=kQLHfJATBTA&eurl=http://www.youtube.com/my_videos_edit2?ns=1&video_id=kQLHfJATBTA&next=%2F my_videos2%3Fpi%3D0%26ps%3D20iurl=http://i4.ytimg.com/vi/kQLHfJATBTA/hqdefault.jpg&feature=player_embedded


this is just the kit bot chassis with unpowered rover wheels and fans

Re: Team 2526 - Propeller Propulsion Prototype.
 

Now that looks really appealing. What props are you using and what motors and gear ratios?

How do you plan to turn, or was this just a little test?

Re: Team 2526 - Propeller Propulsion Prototype.
 

just a test

Re: Team 2526 - Propeller Propulsion Prototype.
 

??

Re: Team 2526 - Propeller Propulsion Prototype.
 

sry

FP direct drive and prop is 10 x 4.7.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Well that's impressive for being so simple. I'd say you should try a bigger prop and a smaller pitch, because you'll increase thrust and decrease stalling.

Technically, a prop with a pitch of 2 would be ideal, seeing as how it's ideal speed is about 10 mph.. and i don't think you'd want to go faster than that.

Re: Team 2526 - Propeller Propulsion Prototype.
 

I guess 1771 just isnt ready to give away that Xerox Creativity award in Atlanta, are they? Hehe

Very nice job guys, you make the EWCP proud. :cool:

Btw, how much power is that sucking out of your battery? Test it out for 2+ minute runs and let us know..

Re: Team 2526 - Propeller Propulsion Prototype.
 

we did all our testing today on one battery and it never droped below 12 volts

Re: Team 2526 - Propeller Propulsion Prototype.
 

We that makes sense, because running propellers doesn't need that much resistance, making the work load fairly easy on the motors. The trick is gearing it so that you get maximum rpm on the prop while getting the max power output out of the motors. XD

Re: Team 2526 - Propeller Propulsion Prototype.
 

Cool idea but does it have enough force to pull the trailer behind you?

Re: Team 2526 - Propeller Propulsion Prototype.
 

You intend on playing on the dark side of the moon, I see.

Re: Team 2526 - Propeller Propulsion Prototype.
 

It doesn't have to have enough force to pull the trailer. Think of it as "bonus force" . . . the wheels drive the bot, and the prop helps. The elegance in this concept is that all (ideally) of the excess potential in the battery is put to use in propulsion.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Yes think of the props as a turbo system for our bot. And no we are not ready to give up our creativity award. We have a few more fairly cool ideas in the works as well. :cool:

Re: Team 2526 - Propeller Propulsion Prototype.
 

yes it could pull the trailer this is just a prototyp the final design will have at least 3 more pounds of thrust

Re: Team 2526 - Propeller Propulsion Prototype.
 

I don't want to rain on anyone's parade but there are a lot of issues raised on this thread that come to mind.
1. It will be necessary for you to demonstrate the safety of your design to both the Lead Robot Inspector and regional officials in order to compete. Read that as the fan must be enclosed so that no one and nothing in the arena may come in contact with it. The enclosure will need to be sufficient to protect everyone and everything from damage should a failure occur.
2. The FP motor curve posted earlier in this thread is for last year's KOP. Remember the motor is changed for this year.
3. Using a fan to move your robot around inevitably will interact with the balls on the field, stated another way, possible herding violation.
4. Please act safely in the shop, holding a rotating knife assy. by hand is not in the best interest of those watching.
5. Centrifical forces generated by the fan/propellor will need to be compensated for if you hope to be accurate where you drive.

Please before you paint yourself into a corner, ask the Q&A if this would be considered a legal design. You have already made this public so asking on the Q&A won't harm your development.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Could you post some pictures or post the video somewhere else? I'm using a school network, and youtube is blocked.

Re: Team 2526 - Propeller Propulsion Prototype.
 

See Q&A (first question answered)

FRC1771

Can a team use model aircraft propellers, mounted in a tube and properly guarded, as a means of propulsion and maneuvering?

GDC
Re: Propellers
There is nothing in the rules that would prevent this, provided there is no damage to field elements and it does not present a safety hazard.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Coming from South Florida where Airboats are prevalent, the noise level of the moving prop is going to be a concern. Most airplanes are noisier than jets.

I can't imagine FIRST allowing robots on the field with a sound pressure level approaching 110-120 dB in an enclosed area. It's loud enough in there as it is.

It would be worse than a Monster Truck performance!

I remember one team in 2006 that tried to implement blowing balls into the lower goal with a stream of air. It worked only when they were up tight against the wall.

I will be wearing my earplugs just in case.

Re: Team 2526 - Propeller Propulsion Prototype.
 

The amount of air going out the back is directly dependent on the pitch of the props, now in order to make this a viable option, we were required to get the smallest pitch we could find (3.75) to keep our rpms up. So that being said, the air speed is not that fast, but its still more air movement than your average housefan (let's just say that i got cold standing behind it, and im from minnesota). We did put a spaceball behind it, and it was able to move it when the ball was a few feet from it and accelerate it from there, but if it starts off much farther, it has hardly any pushing effect on the ball.

This Tuesday, we hope to get a good start on the final two props and possible finish Wednesday or Thursday. With luck we may be able to post another test run before the week is up.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Good Advice.

The FP motor curves are referenced from the KOP section of the 2009 manual. I believe the 9015 motor is the same as last year except for the pinion gear.

Some twin engine aircraft (like my Piper Seneca) have engines and props that rotate in opposite directions. The left and right engines are mirror images of each other. We haven't calculated yet whether this would be necessary. I would expect that torque effects would dominate over inertial effects but there might be advantages to the propwash from counter-rotating props.

At our conceptual design review today, we just adopted a horizontally gimballed thruster composed to two 11 inch props from two FP motors in a 24x12x6 envelope as an optional feature of our design. Whether it survives our next design review remains to be seen.

The rule clarifications take out vectoring thrust in other than the horizontal plane.

Re: Team 2526 - Propeller Propulsion Prototype.
 

We got a little anxious and decided to mount the prototype prop onto our chassis frame just to see it go somewhere :). Here is a short video of it moving only by a single propeller

http://www.youtube.com/watch?v=I24NW...e=channel_page
or
http://www.facebook.com/video/video.php?v=45518718790

We are currently looking for a way to attach the big 54 nub sprocket (its the big one) to our 8mm shaft on the cim motor without using masking tape. If anyone has a way of going about doing this, it would be awesome.

We also tested the vehicle on carpet to test if it will move, it did, but it was really slow and boring, so I never bothered uploading it.

Enjoy

Re: Team 2526 - Propeller Propulsion Prototype.
 

I highly recommend that you use at least the 120A breaker between the battery and the motor to avoid the arcing that can be seen in this video.

Ideally you would have an appropriately sized breaker (40A for a CIM) in place as well but this is a bit tougher with the new PD board than it used to be with the Maxi block.

Re: Team 2526 - Propeller Propulsion Prototype.
 

OK, two fans acocunt for two CIMs, what if you were to use two more CIMs in a conventional drivetrain? Would the extra thrust from the fans provide an advantage?

(hint: yes)

Noise will be an issue, and your safety cage will need to be robust to be sure an exploding prop is fully contained, as well as keeping fingers away. Don't want a bird strike to make you drive into the Hudson river....

Don

Re: Team 2526 - Propeller Propulsion Prototype.
 

I would tend to agree that it is a pretty bad idea to prototype by shorting motors--it's bad for the motor, and dangerous to those around it. What exactly is your procedure for the motor catching fire or the battery melting down. Let's say the Anderson connector's terminals happen to arc and weld themselves together... Please wire through a circuit--it's not hard to set up a simple test board with basic circuitry on it. It doesn't even need to consider of "official first components" instead use a 40 amp fuse and a heavy duty switch--it's safer that way.

Re: Team 2526 - Propeller Propulsion Prototype.
 

well, maybe it would float and then they would have a REAL airboat:D

Re: Team 2526 - Propeller Propulsion Prototype.
 

Gentlemen:

These are incredible dangerous practices - almost beyond belief. Are you trying for a Darwin award? You're in the wrong competition for that.

1. NEVER EVER have people standing around in the plane prop rotation. When (not if) you throw a blade (or even a chain) they could be seriously injured.

2. There should be no extra people anywhere near such a prop until you have it completely shrouded protecting everyone.

3. Use a speed controller. No-one (still living) ever connects an electric prop motor direct to a battery capable of delivering 720 amps like this, especially sitting directly in front of the props direction of travel. The controller will allow you to slowly bring the prop up to speed and check for vibrations, etc.

4. You don't need this on a robot. Make a safe test stand and measure thrust with that.

5. What kind of chain are you using? Are you exceeding the limits onf chain speed? The torque loads on the prop don't call for anything near this.

6. It will not be good for the FRC program to have the kind of injuries you are inviting with this practices. Please stop until you get help from someone that understands the hazards.

Re: Team 2526 - Propeller Propulsion Prototype.
 

Yeah I agree with what you said. We just rushed to mount the prototype in order to disprove any skepticism our team had. So inevitably, safety was the first thing that was overlooked... Atleast everyone wore safety glasses...:(

Re: Team 2526 - Propeller Propulsion Prototype.
 

Personally I think we'd have to do a bit more to win the Darwin award. Yes, I do agree with the safety issue, but we're all humans (at least I think) when we hear something noisy and or something that is spinning really fast everyone tends to crowd around regardless of what anyone else says. Also I'm sure other teams somewhere are doing other dangerous things it's just that they don't post it online. Anyways thank you for your concern we plan to add a cage around the props for our prototype two.