gear ratios

[roboteer49]

I know this has been talked about but all i need to know is for someone to tell me what is the gear ratio to connect a chiaphua and a drill(w/ gearbox)
I am making a gearbox that simply connects the two together w/ spurs
Any other help would be great thanks! :)

[Cory]

Check out JVN's whitepaper in the white papers section. It will allow you to put in the information for each motor and find out what you're looking for.

Cory

[roboteer49]

Is this right:
Chiaphua= 5500 rpm
Drill (no gearbox) =about 19000
The ratio is about 3.5:1

I can't seem to find the rpm of the drill w/ gearbox
I think by having the drill gearbox it will eliminate more gears. I am trying to make the gearbox as simple as possible. Lighter the better :D
Sorry if im sounding stupid

[sanddrag]

Drill no gearbox 19670 rpm
Drill with Bosch Gearbox high gear 1550 rpm
Drill with Bosch gearbox low gear 460 RPM

I personally recommend the team 716 2003 single speed transmission (in the whitepapers). It was fairly simple and lots of fun to build and it worked great. It has a nice low output speed too which is good for big tires. I do suggest you get extra drill gearboxes. You should remove, rotate, and reinstall the motor cage to lock the drill in low gear, then put a blue rubber band over the shifter clips, and then a hose clamp (not too too tight) over that. That method has worked best for us. Make your drill transmissions easily removable and have extra couplers and left hand bolts ready because you will have a transmission fail at least once and the coupler never comes off (a least not without a fight) after it has been run. That's just the nature of the Bosch drill transmission in FIRST robots. But as for all the parts outside of that, flawless.

If you have any questions on the team 716 2003 single speed gearbox, contact Andy Brockway, the designer. We used it this year and made a few slight changes/improvements and have a full inventor model and you can contact me with any questions as well. :)

[RogerR]

the ratio that i've seen the most when connecting the two motors and using a drill gearbox (in high) is 3.5:1, with the 35 tooth being on the chip, and the ten tooth being on the sprocket.

[roboteer49]

haha
I know what u mean, the drill gearbox was the death of our robot this year,
my team wants a dual motor next year so we are going to experiment with that over the summer. Thanks for ur input guys!
Next year I will personally double... no, quadruple check the gearbox :D

[roboteer49]

A few Questions:

RogerR: The ratio for the drill w/ the gearbox is 3.5:1, isn't this the ratio without the gearbox.
Sanddrag: We are going to use 6 inch wheels, should I put the gearbox in high and configure a new ratio or change the ratio from the output shaft to the wheels.

I really apperciate ur guys help :D

[S.Nickens]

You may want rethink using the drill motor geaxboxes, they are more trouble than they're worth. While we didn't use a gearbox, we mated the chip and drill motors to a comon shaft with sprockets and chains. The chip ran a 9 to 9 tooth, while the drill ran a 9 to 32 tooth. The match was so good, the software that was written to equalize the two motors wasn't needed. On the dyno we put out .55 hp.

[sanddrag]

While we didn't use a gearbox, we mated the chip and drill motors to a comon shaft with sprockets and chains. The chip ran a 9 to 9 tooth, while the drill ran a 9 to 32 tooth. While I am able to visualixe this, a picture would be magnificent. Looking at any picture of a drive system is always a learning experience for me Thanks. Also. what pitch chain was it, .1475 ?

[RogerR]

RogerR: The ratio for the drill w/ the gearbox is 3.5:1, isn't this the ratio without the gearbox.
sure is, only reversed. where as you would have the pinion on the drill motor, and the gear on the chip, with the gearbox on the drill, there positions are reversed.

[Ryan F.]

I found a good whitepaper once...I believe it was something like the Who's ctek's....they have a complete design for a gearbox using the chips and drill motors together.

[sanddrag]

I found a good whitepaper once...I believe it was something like the Who's ctek's....they have a complete design for a gearbox using the chips and drill motors together.Yeah, they are team 716 as I stated above http://www.chiefdelphi.com/forums/showpost.php?p=258232&postcount=4

Now, if you want to use the drills in high gear with the Chiaphuas, look at what we (696) did last year or 498 did this year (same thing). Here's a pic http://www.team696.org/forum/image.php?iid=164

If you have any questions about anything drive systems related, send me an e-mail.

[S.Nickens]

While I am able to visualixe this, a picture would be magnificent. Looking at any picture of a drive system is always a learning experience for me Thanks. Also. what pitch chain was it, .1475 ?

Hope this helps. We used .250 ( 1/4 ) pitch chain and sprockets. The large sprocket on the right is driven by the drill motor, you can't quite see the 9 tooth sprocket driven by the chip on the same shaft to the right of the 32. This main shaft also drives two 9 tooth sprockets which go to our reduction sprockets/shafts. There are five sprocket/shafts for the primary drive leading to the wheels.
The setup was very reliable. If you need more specs let me know.

[roboteer49]

What kind of bearings do u use for the drive train?
I need to hav a bearing that can be inserted in the plate like S. Nickens
Also S. Nickens did u have to replace ur gearbox during competition, ive decided to use the gearbox in high with a 3.5:1 ratio w/ the chip.
Im not good w/ rpm, what would be the rpm of of the drive shaft so i can determine the speed, again thanks.

hehe, one last question, is there a way i can determine if the chain i use to connect 2 sprockets will not sag?

[S.Nickens]

What kind of bearings do u use for the drive train?
I need to hav a bearing that can be inserted in the plate like S. Nickens
Also S. Nickens did u have to replace ur gearbox during competition, ive decided to use the gearbox in high with a 3.5:1 ratio w/ the chip
We used 5/16 ID flange bearings the were press fit into the side plates held in place with retaining rings.
We didn't use the gearbox that came with the drill motors. We took out the motors, pressed off the gear and made a custom shaft to adapt to the sprocket shafts. We mounted the drill motor with a custom aluminium mount that also acted as a heat shield. Both motors were mounted to the inner sideplate. I have some AutoCad drawings if you're interested.
The drill motor runs approx. 20,000 rpm, with the reduction of the 32 tooth sprocket it runs 5500 rpm, equal to the chip.The drill runs a 9 to 32 and the chip runs a 9 to 9, so you you have two motors spining a single shaft that spins at 5500 rpm. From there you need to determine your estimated velocity and wheel dia. to determine your final reduction. There are some good white papers to help you figure this out. If I can help answer any more question, just ask.

[Cory]

No offense to Team 11, but I wouldn't use 5/16" bearings/shafts. It just isn't as standard a size as 3/8" or 1/2" or 5/8". a 5/16" also shaft might not be strong enough for some drive systems that have tons of torque.

$0.02

Cory

[sanddrag]

We took out the motors, pressed off the gear and made a custom shaft to adapt to the sprocket shafts. We mounted the drill motor with a custom aluminium mount that also acted as a heat shield. I'm very interested in finding out exactly what this custom shaft and mount are composed of. Is the shaft pressed on? If so, how did you get the proper bore in the shaft? If not, how is it attatched? Also, how does the mount hold the motor and how does it attatch to the gearbox sideplate? If AutoCAD files can be opened in Inventor 5, I'd like to see those. If not, just a describtion and or picture will do. That would be greatly appreciated. Thanks again.

[Brandon Holley]

No offense to Team 11, but I wouldn't use 5/16" bearings/shafts. It just isn't as standard a size as 3/8" or 1/2" or 5/8". a 5/16" also shaft might not be strong enough for some drive systems that have tons of torque.

$0.02

Cory

No offense, but we used this system this year and were easily one of the most powerful bots on the field. We won "most powerful robot" awards from teams. On the dyno we finished 2nd,to the team with a chip, drill, and fisher price per side. All this without one single problem with our drive systems. They worked just fine...

[Brandon Holley]

I'm very interested in finding out exactly what this custom shaft and mount are composed of. Is the shaft pressed on? If so, how did you get the proper bore in the shaft? If not, how is it attatched? Also, how does the mount hold the motor and how does it attatch to the gearbox sideplate? If AutoCAD files can be opened in Inventor 5, I'd like to see those. If not, just a describtion and or picture will do. That would be greatly appreciated. Thanks again.

The custom shaft was mounted onto the drill shaft with a set screw. That shaft then went into our drive side and was coupled together with the rest of the shaft. The mount is basically like a heat sink. It then attaches to the front of the mount into the side plate. Just 2 1/4 20 bolts hold it. I dont have any autocad drawings, but i'll try and get you some.

[S.Nickens]

I'm very interested in finding out exactly what this custom shaft and mount are composed of. Is the shaft pressed on? If so, how did you get the proper bore in the shaft? If not, how is it attatched? Also, how does the mount hold the motor and how does it attatch to the gearbox sideplate? If AutoCAD files can be opened in Inventor 5, I'd like to see those. If not, just a describtion and or picture will do. That would be greatly appreciated. Thanks again.
The adapter shaft for the drill motor was made from 17-4ph steel. The shaft end is .312 dia.the head end of the shaft is .500 dia. x .500 long. The head end was drilled and bored to slip fit over the drill motor shaft, then cross drilled and tapped. We grond a flat on the drill motor shaft and used a set screw to attatch the two. The drill motor mount is 6061 aluminium. The outside dia. is about an inch larger than the the drill motor. It was bored out to allow the drill to slip fit in. Its held in place with two 3/8-24 set screws
that line up with the two flats on the case of the drill motor. The motor slides into the mount shaft first and bottoms out on the mount face. The face of the mount is .625 wide with a .75 dia. thru bore. We drill and tapped two 1/4-20 holes on each side of the .75 bore and bolted the mount to the inside of the chassis side plate. Here's a link to one of our team photo sites
which has some good pics.

http://f2.pg.photos.yahoo.com/ph/berserker717/my_photos
go to build 2001

[Veselin Kolev]

I'm very interested in finding out exactly what this custom shaft and mount are composed of. Is the shaft pressed on? If so, how did you get the proper bore in the shaft? If not, how is it attatched? Also, how does the mount hold the motor and how does it attatch to the gearbox sideplate? If AutoCAD files can be opened in Inventor 5, I'd like to see those. If not, just a describtion and or picture will do. That would be greatly appreciated. Thanks again.


For the question on how the drill motor is mounted to the gearbox plate, there is a thread on that in the Technical forum, called "mounting the drill motor". Might help.

Also, the shaft of the drill motor is a 5 mm shaft. What you do to get a press fit into the new gear, you cut a hole about 0.001" smaller. Yea... if you calculate that, you would have to cut a .1955" hole. That is a really random size, BUT, you can find reamers that size. A reamer is a special cutter that brings a hole to the exact size you want it. You cut a guide hole about 5-10 thousandths smaller and use a reamer.

I haven't replaced the pinion on the drill motor ever, since I use .7 mod gears to mate with it. But, I have replaced the pinion on the Fischer Price motor. What I do is I press off the gear, and press on a .25" shaft with the press hole in it, also a small flat on one side. That way, I just order a .7 mod gear off PIC Design and use the set screw that comes on it, as well as the original bore. That way I can easily change the gear on the motor, say if it breaks or the design changes. Presto, literally. (bad pun)

As for the origninal topic of gear ratios, here are some free load rpms:
drill: 19670
CIM: 5342
FP: 15000

If you want to join the Drill and the CIM, I suggest keeping the drill motor's pinion. To mate it, just use the CIM's keyed shaft. It's an 8 mm shaft with a 2 mm keyway. Just order a .7 mod gear on PIC, bore and key it, and its done. By the way, the 56 tooth .7 mod mates them to 1.4% error. Not bad, not bad at all. That's what I use. To be more exact, go try to find a 55 tooth. Good luck :P.

Here's a pic for Sanddrag on how I got a new gear on the FP motor:

[roboteer49]

I really appreciate u guys helping. I have decided to use the CIM(9:9) and the drill, no gearbox(32:9) I don't want to see another drill gearbox again :mad: all i have to do is figure out how to mount the drill and the sprockets to the motor shafts and i will be done. i will post pics when i am done in a week or so.

[S.Nickens]

I really appreciate u guys helping. I have decided to use the CIM(9:9) and the drill, no gearbox(32:9) I don't want to see another drill gearbox again :mad: all i have to do is figure out how to mount the drill and the sprockets to the motor shafts and i will be done. i will post pics when i am done in a week or so.
Good Luck. When you get it done, you'll be amazed at the power you'll have.