Four wheel drive question [Archive]

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haverfordfords

19-01-2005, 14:39

ajlapp

19-01-2005, 14:45

one way to accomplish this would be to drive one set of wheels directly from the gearbox, and drive the other set with a seperate connector chain which is itself driven by those wheels already powered..

this would require adding another sprocket onto each wheel then adding the chain. you may also need to add a tensioner.....as it is a fairly long span for unsupported chain.

also, look through the gallery. teams have been building four wheel drive robots since the start, and none of them have had a ready made two motor gearbox to start with. so you should be several steps ahead! :)

Mark Pettit

19-01-2005, 14:55

We accomplished it by purchasing the ROBOT-SPROCKETS-2005 kit that is $79.95 at http://www.ifirobotics.com/kitbot.shtml
There are a couple of other threads that already discuss this.

misterfoo

19-01-2005, 15:57

We accomplished it by purchasing the ROBOT-SPROCKETS-2005 kit that is $79.95 at http://www.ifirobotics.com/kitbot.shtml
There are a couple of other threads that already discuss this.

We used 4x drive last year and it was great, this year we are modifying the setup to have the same. I have not checked with the mech team this week, but I know the conversion is underway from 2 wheel to 4 wheel drive.

If you want to be very simple, you could order a double chain sprocket from Mcmaster. We also converted our wheels to use 5/8 shaft with a similar sprocket and a keyway.

Here is what I found.

http://www.mcmaster.com/

Search for Double-Strand (page 932)

Steel Double-Strand Plain-Bore Sprockets for ANSI #35-2 to #60-2 Roller Chain

DDRAngelKurumi

19-01-2005, 16:16

We are just ordering more parts, because we are doing 4-wheel drive too.

GOOD LUCK!

Mark Pettit

19-01-2005, 16:17

If you want to be very simple, you could order a double chain sprocket from Mcmaster. We also converted our wheels to use 5/8 shaft with a similar sprocket and a keyway.

Please be careful of the advice you are presenting.
The sprockets that came in the kit are custom bored to fit on the kit-tranny shaft. You can't purchase stock sprockets and expect them to fit out of the box. They need to be bored out or at least pressed onto the shaft. This is the 4th time I've had to remind people of this in as many threads, such as this one (http://www.chiefdelphi.com/forums/showthread.php?t=32704&highlight=custom+bored).

JVN

19-01-2005, 16:29

Hi all,

For those of you that are creating robots with four wheel drive, how are you accomplishing this? The included gear box only supports two wheel drive and in order to get it to work four wheel drive you need two of part # FRC-2005-112-009.

Innovation First claims that they, "do not sell the transmission gears or sprockets individually. The gear you are looking for is included in the transmission kit. We only sell transmission kits in complete sets."

A complete set would be ridiculously expensive. My question therefore is how do you go around this technicallity to support four wheel drive, OR how did you order the two parts for four wheel drive without buying the whole set, OR does anyone have any extra of these parts?

If anyone could help out this rookie team, we would greatly appreciate it.

Thank you all,
Jason, Team Leader 1656
Jason,
Innovation First DOES sell sprockets individually, but not gears.
Please refer to this page: http://www.ifirobotics.com/kitbot.shtml

Note: you do not need any additional GEARS to make a 4WD system, only sprockets. You can buy 1 sprocket kit "ROBOT-SPROCKETS-2005" and along with the 2 extra wheels and wheel hubs included in the kit be 4-wheelin' before you know it.

The gearbox is easily convertable to a 4WD configuration. In fact, it was originally designed with 4WD in mind. If you simply buy the extra sprockets, you will be up and ready to go in no time.

If you have more problems, do not hesitate to ask,
John

robolemur1236

19-01-2005, 16:31

why cant you make the robot 4 wheel drive with just ordering two more sprockets? add those to the ends of the drive shaft, drop another chain, presto! four wheel drive

JVN

19-01-2005, 16:44

Refer to attached.
Here are 3 configurations of chain/wheels I sketched up in Paint that may be useful.
Two are 4WD, using different sprocket/chain combos.
One is 6WD.

Just some food for thought.
John

Edit:
Please note, these are just some ideas, there are TONS of ways to reconfigure a drivetrain, and the KOP chassis can be used for quite a few. Every team must decide what seems best.
/Edit

caffel

19-01-2005, 18:27

Paul Copioli

19-01-2005, 19:02

Use MSC Direct or McMaster Carr or KartWorld.com.
Buy # 35 chain plate sprockets (no hub needed).
Drill a circle of holes using the wheel flange as a template.
Bolt directly to the wheel flanges.

No! You can not use just plate sprockets. The #35 chain will rub against the wheel if you do not have the hub on the sprocket. The hub (1/4" hub projection) on the kit sprocket is the shortest I recommend and still have the chain be a safe distance away from the wheel.

-Paul

Max Lobovsky

19-01-2005, 19:03

No! You can not use just plate sprockets. The #35 chain will rub against the wheel if you do not have the hub on the sprocket. The hub (1/4" hub projection) on the kit sprocket is the shortest I recommend and still have the chain be a safe distance away from the wheel.

-Paul
Then simply add a spacer on your bolts.

JVN

19-01-2005, 19:06

Then simply add a spacer on your bolts.
I recommend the following spacer, if you take this approach.
It will put your chain out a safe distance from the skyway wheel.
The OD of the spacer will fit into the hex indents on the wheel hub.

Spacer – 10-32 Screw, 5/16” OD, 9/16” Length
McMaster Part No. - 94639A786

John

haverfordfords

20-01-2005, 00:53

Jason,
Innovation First DOES sell sprockets individually, but not gears.
Please refer to this page: http://www.ifirobotics.com/kitbot.shtml

Note: you do not need any additional GEARS to make a 4WD system, only sprockets. You can buy 1 sprocket kit "ROBOT-SPROCKETS-2005" and along with the 2 extra wheels and wheel hubs included in the kit be 4-wheelin' before you know it.

The gearbox is easily convertable to a 4WD configuration. In fact, it was originally designed with 4WD in mind. If you simply buy the extra sprockets, you will be up and ready to go in no time.

If you have more problems, do not hesitate to ask,
John

Thank you everyone for your great suggestions!!! So if I read this correctly, all we need is ROBOT-SPROCKETS-2005 and that has the parts we need? AWESOME! Please just confirm this and we will order that right away. Thanks again!

JVN

20-01-2005, 01:16

Thank you everyone for your great suggestions!!! So if I read this correctly, all we need is ROBOT-SPROCKETS-2005 and that has the parts we need? AWESOME! Please just confirm this and we will order that right away. Thanks again!That's affirmative.
With the "ROBOT-SPROCKETS-2005" Kit ($80 + shipping) you can construct the 4WD configuration I show on the right in my above post.

Isn't that awesome?
Less than $100 for a fully working 4-motor, 4WD base.
It's a brave new world.

JV

Andy Brockway

20-01-2005, 12:13

That's affirmative.
With the "ROBOT-SPROCKETS-2005" Kit ($80 + shipping) you can construct the 4WD configuration I show on the right in my above post.

Isn't that awesome?
Less than $100 for a fully working 4-motor, 4WD base.
It's a brave new world.

JV

You will also need the wheel adapters or make your own. IFI is currently out of stock. I was planning on making four plates and using only one wheel adapter per wheel. The plate would go on the opposite side from the sprocket. There are drawings for wheel adapters on the FIRST CAD library.

haverfordfords

20-01-2005, 19:32

I saw this FAQ on the IFIrobotics.com Site...

So, we also need the sold out hubs? Does this mean we also need an additional chain OTHER than the one included. Also, the sprockets listed below - those are IN ADDITION to the ones already in the kit (all four of them?), correct?

Sorry if this is a stupid question...

Thanks,
Jason

"What do we need and how do we make a four wheel drive system out of what we have in the kit?

Please check section 3 in the "2005 FIRST Robotics Competition Kit Transmission Manual -RevA" document located at http://www.ifirobotics.com/kitbot.shtml.

You do not need the custom PVC spacer used in the 2 wheel drive configuration and you need to use the 40mm key provided in the kit instead of the 20mm key. You also need additional parts to make the 4 wheel drive configuration. The additional parts you need are:

1. 21 tooth sprocket - Quantity 2. Available from ifirobotics.com
2. 28 tooth sprocket - Quantity 2. Available from ifirobotics.com
3. Skyway wheel hubs - Quantity 2 sets.
4. 10' of chain. Available from ifirobotics.com"

elknise

20-01-2005, 21:44

Kit Bot Parts (http://www.ifirobotics.com/kitbot.shtml)

I just found out yesterday that IFI now sells individual sprockets of both kinds for 19.99$

haverfordfords

21-01-2005, 10:46

Kit Bot Parts (http://www.ifirobotics.com/kitbot.shtml)

I just found out yesterday that IFI now sells individual sprockets of both kinds for 19.99$

Yes, but according to that FAQ it seems that we need 2 of BOTH anyway? Is that true?

MattB703

21-01-2005, 11:38

Yes, but according to that FAQ it seems that we need 2 of BOTH anyway? Is that true?

Well, you should need a total of 4 big sprockets, one for each wheel, and a total of 4 small sprockets, 2 on each geabox output. Then you will put 4 separate chains, one to each wheel. You could run with only 1 sprocket on each output and use one longer chain to turn both wheels on that side but I'd advise against it. You would need to make a semi elaborate idler system to get an adequate (more that 150°) of chain wrap on the drive sprocket.

Paul Copioli

21-01-2005, 12:09

Quote:
Originally Posted by haverfordfords
Yes, but according to that FAQ it seems that we need 2 of BOTH anyway? Is that true?

Well, you should need a total of 4 big sprockets, one for each wheel, and a total of 4 small sprockets, 2 on each geabox output. Then you will put 4 separate chains, one to each wheel. You could run with only 1 sprocket on each output and use one longer chain to turn both wheels on that side but I'd advise against it. You would need to make a semi elaborate idler system to get an adequate (more that 150°) of chain wrap on the drive sprocket.

In either case, you need more than just the wheel sprockets. For the 4 chain option (two per transmission) as documented in the kit you need four output sprockets (two per transmission). For the two chain option (one per transmission), you will need at least one idler per side.

Bottom line, for four wheel drive you need more hardware than just two more wheel sprockets. That is why IFI packaged the sprockets together.

-Paul

BlazinFire47

25-01-2005, 13:10

well.... you can forsay create your own 4-wheel drive system you know.... but it does involve lots of build time and 3 weeks have passed now.... to keep it sweet and simple.... 4-wheel drive will not a big issue this year.... i forsee that most teams will be using 2 wheel drive or swerve.... so if it is easier right now use 2- wheel drive for the timeframe we have right now... :D

csquared05

25-01-2005, 22:10

Alan Anderson

25-01-2005, 23:13

last year we used 4 wheel drive, but it was extremely jumpy on the carpet last year when we were turning with the supplied wheels. We improved our control by using zip ties, but they weren't 100% effective. How have other teams overcome this jerkiness?
A TechnoKat robot from a few years ago used a pneumatic "puck" that lifted the front end of the robot when the joysticks were calling for a turn. This was on a tank-tread drivebase rather than a four-wheel drive, but the idea works either way.

If you aren't dead set on the supplied wheels, you have many options, including omniwheels. The 2004 KatsKlaw just used extremely grippy rear tires and enough motor power to make the front wheels slip without too much skipping.

haverfordfords

25-01-2005, 23:15

A TechnoKat robot from a few years ago used a pneumatic "puck" that lifted the front end of the robot when the joysticks were calling for a turn. This was on a tank-tread drivebase rather than a four-wheel drive, but the idea works either way.

If you aren't dead set on the supplied wheels, you have many options, including omniwheels. The 2004 KatsKlaw just used extremely grippy rear tires and enough motor power to make the front wheels slip without too much skipping.

What are your thoughts on using the supplied wheels as the power (attached to the motors) with omniwheels as the front wheels? This way there would be no drag on the front tires it would go freely either direction?

Alan Anderson

25-01-2005, 23:24

What are your thoughts on using the supplied wheels as the power (attached to the motors) with omniwheels as the front wheels? This way there would be no drag on the front tires it would go freely either direction?
Indeed, that's exactly how we have built the kitbot for testing purposes this year. Though the omniwheels aren't really designed to be freewheeling, it works. It seems to give a little more of a bumpy ride than I would have expected, but that might just be due to the lightness of the front end of the chassis.