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This drivetrain uses sprockets and chain to transmit motion from the UltraPlanetary Gearbox and Drive Shaft to the rest of the drivetrain. The figure below shows the major components of chain.
Outside Links consist of two outside plates which are connected by two pins that are pressed into each plate. The pins in the outside link go through the inside of the hollow bushings when the inner and outer links are assembled. The pins can freely rotate on the inside of the bushings.
Inside Link consist of two inside plates that are connected by two hollow bushings which are pressed into each plate. The teeth of the sprocket contact the surface of the bushings when the chain is wrapped around a sprocket.
Pitch is the distance between the centers of two adjacent pins. The REV 15mm Build System uses #25 (0.25”) chain.
To find more information about chain check out the Sprocket and Chain section.
In the FTC Starter Kit is a #25 Chain Tool. This custom-designed tool allows teams to easily break and re-assemble #25 chain. The mandrel is used to push out the chain pin. If using master links, the pin can be completely removed, but the depth guide screw allows the option of partially pressing out the pin and then re-assembling without master links.
For more information on the #25 Chain Tool, see the Chain Tool page and How To video.
For this drivetrain, four chain loops that are 56 links long (14 inches or 35.56 cm in length) are needed. When counting links for chain, both the inner and outer links need to be counted. Counting the number of bushings is another way to get the correct chain length. To successfully reform chain, the total count of links must be an even number with one inner link and one outer link exposed. This allows the chain tool to press the pin back into the bushing, through an inner and outer link, reconnecting the chain. Below are the steps to use the #25 Chain Tool to reset the pin into the chain. If you would like to use master links see the #25 Chain Tool page for more information.
The steps below show how to make a chain loop and call out the specific link counts for the correct chain loop needed to complete this guide. The images use a smaller chain link sample. Make sure you make chain loops that are 56 links long (14 inches or 35.56 cm in length).
Unscrew the Pin Screw and Compression Screw such that they are flush with the chain channel.
Ensure the Cup Point Set Screw is fully engaged in the Chain Tool.
Insert #25 chain into the chain channel and align the desired link between the two vertical pins in the channel.
Note: Count 56 bushings from an exposed inner link.
Next secure the chain in place with the compression screw. Tighten until the chain cannot shift within the channel.
Note: Be careful to not overly push the pin out in the next step it will be impossible to put it back in, and a master link will be needed. As result of manufacturing tolerances, the cup point set crew may be close enough to use as a hard stop for the pin.
Screw the Pin Screw down until the pin almost touches the Cup Point Set Screw. The user should stop pushing the pin out before it leaves the back plate the outer link. Considerable pressure will be felt before the pin comes all the way out. Removing the chain from the tool to check if the pin is fully unseated from the bushing is recommended.
The final result will be the pin still partially connected to the chain (see photo as example).
Put the Inner Link bushing into the Outer Link. Align the Pin in the Compression Screw hole.
Turn the Compression Screw until the Pin is fully seated back into the chain channel.
56 Link Chain Assembly Complete Repeat these steps step until you have four 56 Link Chain Assemblies.
This section outlines the steps required to build a six-wheel, channel-based, differential drivetrain. This design is a good starting point. However, modification maybe required to address the specific needs of the robot being designed. This design is flexible, allowing for different wheel types depending on the overall requirements of the drive train.
The assembly of this drivetrain is broken into a few sections. This allows for a team of people to work on different tasks to complete the build quicker. Each section begins with what parts and the quantity of parts needed to complete the steps in that section. A list of required materials for all sections is listed below.
The Channel Drivetrain is built out of the following kits:
Part Number
Description
QTY.
FTC Starter Kit V3
1
Part Number
Description
QTY.
FTC Starter Kit V2
1
V2 To V3 Update Bundle
1
PART NUMBER
DESCRIPTION
QTY.
45MM X 15MM C CHANNEL - 408MM
4
45MM X 15MM C CHANNEL - 248MM
1
U CHANNEL ENDCAP
4
15MM EXTRUSION - 420MM
2
5MM X 90MM HEX SHAFT
6
3MM SPACER
12
15MM SPACER
2
THROUGH BORE BEARING - SHORT
14
THROUGH BORE BEARING - LONG
4
10 TOOTH #25 SPROCKET
8
#25 ROLLER CHAIN - 10 FT
1
M3 STANDOFF - 40MM
8
TENSIONING BUSHING - 39MM
8
SHAFT COLLAR
12
ULTRAPLANETARY GEARBOX KIT & HD HEX MOTOR
2
ULTRAPLANETARY OUTSIDE MOUNTING BRACKET
2
15MM PLASTIC 90 DEGREE BRACKET
12
90MM GRIP WHEEL
4
90MM OMNI WHEEL
2
M3 X 8MM HEX CAP SCREWS - 100 PACK
1
M3 NYLOC NUTS - 100 PACK
1
PART NUMBER
DESCRIPTION
QTY.
15MM SPACER
1
3MM SPACER
2
THROUGH BORE BEARING - SHORT
2
SHAFT COLLAR
1
10 TOOTH #25 SPROCKET
1
5MM X 90MM HEX SHAFT
1
Add a Shaft Collar flush to the end of the 5mm x 90mm Hex Shaft.
Tighten the Shaft Collar.
Slide a Through Bore Bearing – Short onto the shaft.
Note the smaller portion of the bearing faces towards the Shaft Collar.
Slide a 3mm Spacer onto the shaft.
Slide a 10 Tooth # 25 Sprocket onto the shaft.
Slide a 15mm Spacer onto the shaft.
Slide a 3mm Spacer onto the shaft.
Slide a Through Bore Bearing – Short onto the shaft.
Note the smaller portion of the bearing faces away from the Shaft Collar.
SINGLE SPROCKET ASSEMBLY COMPLETE
Repeat the above steps until there are two completed Single Sprocket Assemblies. Set aside for later.
PART NUMBER | DESCRIPTION | QTY. |
3MM SPACER | 4 |
THROUGH BORE BEARING - SHORT | 3 |
SHAFT COLLAR | 2 |
10 TOOTH #25 SPROCKET | 1 |
5MM X 90MM HEX SHAFT | 1 |
90MM OMNI WHEEL | 1 |
DRIVE SHAFT ASSEMBLY STEPS |
Add a Shaft Collar flush to the end of the 5mm x 90mm Hex Shaft. Tighten the Shaft Collar. |
Slide a 90mm Omni Wheel onto the shaft. |
Slide a Through Bore Bearing – Short onto the shaft. Note the smaller portion of the bearing faces towards the Shaft Collar. |
Slide a Through Bore Bearing – Short onto the shaft. Note the smaller portion of the bearing faces towards the Shaft Collar. |
Slide a 3mm Spacer onto the shaft. |
Slide a 10 Tooth # 25 Sprocket onto the shaft. |
Slide a Shaft Collar onto the shaft. Keep this Shaft Collar loose. |
Slide a 3mm Spacer onto the shaft. |
Slide a 3mm Spacer onto the shaft. |
Slide a 3mm Spacer onto the shaft. |
Slide a Through Bore Bearing – Short onto the shaft. Note the smaller portion of the bearing faces away from the Shaft Collars. |
DRIVE SHAFT ASSEMBLY COMPLETE Repeat the above steps until there are two completed Drive Shaft Assemblies. Set aside for later. |
Channel Drivetrain Resources
PART NUMBER | DESCRIPTION | QTY. |
3MM SPACER | 2 |
THROUGH BORE BEARING - SHORT | 2 |
SHAFT COLLAR | 1 |
10 TOOTH #25 SPROCKET | 2 |
5MM X 90MM HEX SHAFT | 1 |
Add a Shaft Collar flush to the end of the 5mm x 90mm Hex Shaft. Tighten the Shaft Collar. |
Slide a Through Bore Bearing – Short onto the shaft. Note the smaller portion of the bearing faces towards the Shaft Collar. |
Slide a 3mm Spacer onto the shaft. |
Slide a 10 Tooth # 25 Sprocket onto the shaft. |
Slide a 10 Tooth # 25 Sprocket onto the shaft. |
Slide a 3mm Spacer onto the shaft. |
Slide a Through Bore Bearing – Short onto the shaft. Note the smaller portion of the bearing faces away from the Shaft Collar. |
DOUBLE SPROCKET ASSEMBLY COMPLETE Repeat the above steps until there are two completed Double Sprocket Assemblies. Set them aside for later. |
The FTC Starter Kit comes with two of the UltraPlanetary Gearbox Kits with HD Hex Motors. This is an entry point into using the REV UltraPlanetary System. There are three UltraPlanetary Cartridges supporting seven different final gear reductions ranging from nominally 3:1 to 60:1. This allows for the right amount of torque for the application at hand. The motor provided already has the pinion gear pressed onto it making assembly of gearboxes easier.
When getting started with this drivetrain, it is recommended to use a nominal 20:1 Gear Ratio. This uses the UltraPlanetary 5:1 Cartridge and the UltraPlanetary 4:1 Cartridge. For more information on all gear ratio options, load ratings, and more, see the UltraPlanetary Gearbox User’s Manual on revrobotics.com.
Remove the set screw from the UltraPlanetary Output before attaching the Outside Mounting Plate.
You may need to go tension the chain on the drive rail. To do so, adjust the tensioning bushing up or down the slot they are fastened in to get the correct tension. See the section for guidance.
PART NUMBER
DESCRIPTION
QTY.
15MM PLASTIC 90 DEGREE BRACKET
12
M3 X 8MM HEX CAP SCREWS
60
M3 NYLOC NUTS
60
Take a bracket and finger start one Hex Cap Screw and Nyloc Nut per hole.
Note: The side of the bracket with “ribs” must have the Hex Cap Screw head.
PRE-LOADED BRACKET COMPLETE
Repeat this step until you have twelve Pre-Loaded Brackets.
PART NUMBER
DESCRIPTION
QTY.
45MM X 15MM C CHANNEL - 248MM
1
15MM EXTRUSION - 420MM
2
THROUGH BORE BEARING - SHORT
2
THROUGH BORE BEARING - LONG
4
90MM GRIP WHEEL
4
90MM OMNI WHEEL
2
SHAFT COLLAR
6
ASSEMBLIES
DRIVE RAIL ASSEMBLY
2
PRE-LOADED BRACKET
12
FINAL ASSEMBLY STEPS
Slide the four Pre-Loaded brackets onto the Drive Rail Assembly as shown.
Align the Pre-Loaded Brackets where 6 Hex Cap Screws and Nylock Nuts are exposed.
Add two Pre-Loaded Brackets to the Motor side C Channel.
Have the edge of the bracket roughly at the center of the large (9mm) hole. Start with the second hole to the right of the Double Sprocket Assembly.
Tighten the Nyloc Nuts until they are snug
Slide the 45mm X 15m C Channel - 248MM onto the Preloaded Brackets as shown.
Tighten the Nyloc Nuts until they are snug.
Repeat sliding four Pre-Loaded brackets onto the other Drive Rail Assembly as shown.
Repeat aligning the Pre-Loaded Brackets where 6 Hex Cap Screws and Nylock Nuts are exposed.
Repeat adding Pre-Loaded Brackets to the Motor side C Channel.
Have the edge of the bracket roughly at the center of the large (9mm) hole. Start with the second hole to the right of the Double Sprocket Assembly.
Tighten the Nyloc Nuts until they are snug
Slide the second Drive Rail on.
Once in place, tighten the Nyloc Nuts until they are snug.
Slide two pieces of 15mm Extrusion – 420mm into the Pre-Loaded Brackets until they are through both sets brackets. One 15mm Extrusion is for the top and the other for the bottom.
Align the 15mm Extrusion – 420mm so approximately the same amount of Extrusion is left on the end of each Bracket.
Tighten the Nyloc Nuts until they are snug.
Add a Through Bore Bearing – Short to both of the Drive Shafts and Through Bore Bearing – Long to the remaining shafts.
Note: the smaller section on the bushing faces away from the Channel
Take the Grip and Omni wheels and place on the shafts as shown.
Add one shaft collar to the end of each shaft.
Tighten down the shaft collars on each wheel to secure them in place.
DRIVETRAIN COMPLETE
PART NUMBER | DESCRIPTION | QTY. |
M3 X 8MM HEX CAP SCREWS | 6 |
ULTRAPLANETARY OUTSIDE MOUNTING BRACKET | 1 |
PARTS WITHIN THE ULTRAPLANETARY GEARBOX KIT |
HD HEX MOTOR | 1 |
ULTRAPLANETARY PINION GEAR (ON HD HEX MOTOR) | 1 |
ULTRAPLANETARY MOUNTING PLATE | 1 |
ULTRAPLANETARY CARTRIDGE 4:1 | 1 |
ULTRAPLANETARY CARTRIDGE 5:1 | 1 |
ULTRAPLANETARY OUTPUT STAGE | 1 |
M3 X 30MM CAP HEAD SCREW | 6 |
M3 X 8MM BUTTON HEAD SCREW | 2 |
Attach the UltraPlanetary Mounting Plate to the HD Hex Motor using two 8mm Button Head Screws. Note: Use the 2mm Allen Key to tighten these screws. |
Seat the UltraPlanetary 5:1 Cartridge onto the input pinion. Note: Placing a finger on the output of the 5:1 Cartridge and turning it helps for placement. |
Seat the UltraPlanetary 4:1 Cartridge onto the UltraPlanetary 5:1 Cartridge. Note: Placing a finger on the output of the 4:1 Cartridge and turning it helps for placement. |
Seat the UltraPlanetary Output Stage onto the UltraPlanetary 4:1 Cartridge. Note: Placing a finger on the output of the Output Cartridge and turning it helps for placement. |
Insert six of the 30mm Cap Head Screws into the holes in the outer ring off the Output Cartridge. Tighten these screws down until they are snug not tight using a 2.5mm allen wrench. Note: The 30mm length is the 2nd longest screw provided with the UltraPlanetary Gearbox Kit. |
Align the UltraPlanetary Outside Mounting Bracket with the mounting holes on the Output Cartridge. |
Insert six 8mm Hex Cap Screws into the mounting holes. Tighten the screws until they are snug. |
ULTRAPLANETARY ASSEMBLY COMPLETE Repeat the above steps until there are two completed UltraPlanetary Assemblies. Set aside for later. |
PART NUMBER | DESCRIPTION | QTY. |
45MM X 15MM C CHANNEL - 408MM | 2 |
U CHANNEL ENDCAP | 2 |
M3 STANDOFF - 40MM | 8 |
TENSIONING BUSHING - 39MM | 8 |
M3 X 8MM HEX CAP SCREWS - 100 PACK | 1 |
M3 NYLOC NUTS - 100 PACK | 1 |
ASSEMBILIES |
SINGLE SPROCKET ASSEMBLY | 1 |
DOUBLE SPROCKET ASSEMBLY | 1 |
DRIVE SHAFT ASSEMBLY | 1 |
ULTRAPLANETARY ASSEMBLY | 1 |
56 LINK #25 CHAIN LOOP | 1 |
Place M3 Screws and M3 Lock Nuts in the correct locations. Tighten until nuts are snug. Note: The Output Cartridge of the UltraPlanetary Gearbox lines up with the fourth large (9mm) hole from the end of the C Channel. |
Attach a U Channel End Cap to the Motor end of the C Channel. Add three Hex Cap Screws to hold it in place. Tighten the Hex Cap Screws. |
Attach a U Channel End Cap to the other end of the C Channel. Add three Hex Cap Screws to hold it in place. Tighten the Hex Cap Screws. |
Align the Hex of the shaft with the UltraPlanetary Gearbox. Insert the Drive Shaft Assembly into the UltraPlanetary Female Hex output. |
Remove the Shaft Collar, Omni Wheel, and one Through Bore Bearing – Short from the Drive Shaft Assembly. |
Remove the Shaft Collar from the Single Sprocket Assembly. Set aside for use later. |
Remove the Shaft Collar from the end of the Double Sprocket Assembly. Set aside for use later. |
Insert the Double Sprocket Assembly, short end towards the Motor, into the thirteenth large (9mm) hole from an End Cap. |
Add a Shaft Collar to the end of the shaft. Tighten down the set screw. |
Insert the Single Sprocket Assembly, sprocket side toward the motor, into the fourth large hole from the non-Motor End Cap. |
Add a Shaft Collar to the end of the shaft. Tighten down the set screw. |
Add four M3 Standoffs - 40MM along the C Channel for chain tension with M3 Hex Cap Screws. Add Tension Bushings onto each Standoff Note: See the next step for locations. |
Tighten down the Hex Cap screws once the Standoffs are in the correct locations towards the bottom of the slotted holes. Note: Screws should be tightened just enough to hold the standoffs in place. Chain tension is adjusted later in the drive rail construction. |
Add the 56 Link Chain Loop to the Sprockets. Note: Keeping the Standoffs with Tensioning Bushings loose can help getting the chain loops on the Drive Rails. |
Take a 45mm X 15mm C Channel – 408mm and seat the large holes on the bearings on each shaft. Note: Make sure the bearings are square and the Channel End Cap holes line up. |
Take ten Hex Cap Screws and secure the 45mm X 15mm C Channel – 408mm to the rest of the assembly. Screw into the End Caps and the Standoffs to keep the chain tensioned. |
DRIVE RAIL ASSEMBLY COMPLETE Repeat this step until you have two Drive Rail Assemblies. |
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