help me design a custom parallel plate drive train

To design a custom parallel plate drivetrain, you should start by sketching a 2D layout of a four-motor, belted drive pod in CAD, keeping the plates under three inches apart and using 1/8-inch aluminum plates to maximize internal space and structural rigidity. According to Game Manual 0's Drivetrains section, a parallel plate drivetrain consists of two plates per drive pod, with the wheels and power transmission sandwiched between them. Keeping the pod width to three inches or less is ideal because it leaves more room in the center of the robot for mechanisms like intakes. Game Manual 0's CAD Tutorials suggest using 1/8-inch thick aluminum plates (though 3/32-inch is an option) and starting with a detailed 2D sketch to map out all mounting holes, bores, and center-to-center distances before extruding.

For power transmission, belts and pulleys are highly recommended over direct drive, which is fragile under shock loads. Game Manual 0's Drivetrains section advises avoiding direct drive because gearboxes can easily break when the wheels experience sudden impacts. When placing your motors, Game Manual 0's CAD Tutorials recommend face-mounting them to the inner plate as low as possible to keep the center of mass low, and using planetary gearboxes rather than spur gearboxes to better handle shock loads.

To assemble the drive pods, use standoffs or churro tubes placed strategically where support is needed, leaving enough clearance for wheels, pulleys, and spacers. Game Manual 0's CAD Tutorials explain that you can connect the two completed drive pods using channel, extrusion, or a custom u-brace to stiffen the chassis. Additionally, you should design the plates with 0.25 to 0.5 inches of ground clearance to prevent the robot from dragging on the foam tiles, and you can pocket the plates to reduce weight as long as you do not compromise their structural integrity.

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CAD Tutorials > CAD Tutorial Part 1 - Drivetrain in an Hour > Designing the Drivetrain Plates

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After learning the CAD software, it's time to start the actual design. Here are some things to figure out before starting:

Drive Type (mecanum, 6wd, 8wd, etc.)
Number of Motors (four motors recommended in most cases)
Type of wheels (Traction, omni, etc.)
Drive power (belt, chain, gear)

To keep it simple, this example uses a 4 wheel tank drive using four motors. The wheels selected are 2 Colson wheels for traction, and 2 omni wheels to aid in turning.

First, make the left side of the drivebase. After completing it, all you have to do is mirror the left side to the right, so you don't have to do each side individually. Start with a 2D sketch of everything before trying to extrude and make actual 3D objects.

This is a sketch of the inner plate of the drive base. Everything should be laid out in a 2D sketch to determine the mounting holes, bore, center-to-center distance, etc. 2D sketches are extremely helpful and are highly recommended in any project. After the sketch is completed, everything else falls into place and becomes pretty simple.

After this, extrude that sketch into the first plate of the drivetrain. Typically, a standard thickness of aluminum plate is 1/8". Thinner plate (3/32") can be used as well, but generally most teams stick to 1/8". Extrude the plate to that thickness. Below is the sketch after extruding.

The next step will be making the outer plate for the drivebase. It is even faster to do than the inner. To do this, simply create a new part. Go back to your inner plate and start a 2D sketch.

After starting the new sketch on the inner plate, hit "Project Geometry" and just click anywhere on the part. It should highlight every outline of the part. (Shown here is a yellow line; yours might be red, blue or some other color.) Now click and drag across the part selecting every line on the screen. Now go hit CTRL + C, then go to the new part and hit create 2D Sketch. Next hit CTRL + V.

It should look like an exact copy of the inner plate but now as a sketch. Delete your motor mounts out of the middle, then extrude the outer plate.

This is what the outer plate looks like, an almost exact copy of the inner one without the holes for the motors. Now with those two plates made, it's really just time to assemble the rest of the drivetrain, which is by far the most time consuming. Now, for some info on what to use to attach the two plates together, generally standoffs or churro is highly recommended. To attach the two halves of the drivetrain, use either channel, extrusion, or a custom u-brace. Some teams prefer a custom brace as it is a good way to stiffen up the drivetrain while requiring very little maintenance over the season. It is possible to use peanut extrusion or kit channel, which alternatively works just as well.

Note that when using a custom drivetrain, you can cut out material from your drivetrain plates. This process is called pocketing. While not a vital step, pocketing helps you save weight. However, be careful not to remove too much material; if done, the plates become less sturdy. More about pocketing is in the next section.

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Machining

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Machining allows teams to create practically any part without limitations.
Machining allows teams to create custom drivetrain plates, arms, linear slides, etc to fit their design needs more effectively than kits.
Machining is cool. Yes, really.

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Pedro Pathing > Custom Drivetrain

Pedro Pathing·No licence published — summarised, never reproduced

Summarised above in Sharp AI’s own words. The original text is not reproduced here — open the source to read it.

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Pedro Pathing > Custom Drivetrain

Pedro Pathing·No licence published — summarised, never reproduced

Summarised above in Sharp AI’s own words. The original text is not reproduced here — open the source to read it.

Open Pedro Pathing

CAD Tutorials > CAD Tutorial Part 1 - Drivetrain in an Hour > Additional Considerations

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A general rule of thumb for most teams is the wider the intake, the better the chance of picking up the game piece. However, this is super game dependent. If you need to pick up a 6" cube like in Relic Recovery then you would not need 14" of space for your intake.

However, if you need to pick up a ball like in Velocity Vortex, the bigger the intake gives you better chances of grabbing the balls. Keep this in mind when designing drive pods - try to keep them as thin as possible without sacrificing rigidity and strength to maximize space for other mechanisms and wiring.

Connecting your two plates together is really simple. Some standoffs or churro extrusion from AndyMark is a relatively easy way to connect them together with a few bolts. Just make a few 1/4 in. holes in your sketch where you want the churro tube to be. Decide how long the churro needs to be. Remember to leave enough space between the plates for your wheels, pulleys, sprockets, and spacers. You don't need to go overkill on how many standoffs you need in between your plates; however, put them in strategic places where support is needed.

Shown below is a drive pod, which is one half of the drivetrain, including the shafts, bearings, wheels, motors, belts, etc. In short, the drive pod has everything that will be built in real life. This particular one is the left side, but to make the right side create an offset plane, select the mirror tool, then hit mirror.

After mirroring the drive pod to make your opposite side, connect those two halves together and you're done with the drivetrain. Below is a rendering of the complete drivetrain in CAD.

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CAD Tutorials > CAD Tutorial Part 1 - Drivetrain in an Hour > Additional Considerations

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Powering wheels can be done is a couple different ways through either belts and pulleys, chains and sprockets, gears, or even powered directly from the motor. Direct drive and chains are the simpler of the options, with direct drive not needing a calculated distance at all just have to set the motor exactly where the center of the wheel is. Chains allow for a little bit of slack not needing an exact center to center distance in the wrap like belts and pulleys do. Finally gears which need to be a certain distance apart from each other to mesh properly and not skip or bind.

Mounting motors is done in a plate style by face mounting the motor into the innermost drivetrain plate. It can also be done by mounting the motors to a 3rd plate, located in between the outside and inside. This allows for the motor to take up less space in the middle of the robot, but adds complexity. Motors should always be as low as possible and depending where you want the center of mass, either the middle or towards the back of the robot. It is also worth keeping in mind the type of power transmission and the expediency of doing so in light of the motor placement.

Ground clearance is all dependent on if there are any obstacles on the field, as well as what your team wants to do in that game in regards to said obstacles.

For example, in Rover Ruckus some teams with tank drivetrains decided to enter the crater. Therefore, they left enough space to not beach themselves on top of the crater, a common mistake that inexperienced teams often make.

Other teams decided to ignore driving over the crater and decided to reach over with an arm or slide system, which meant they didn't need a lot of ground clearance for their drivebase.

Typically, anywhere from .25 inches of clearance to .5 inches (if you want to be safe) on a completely flat field will allow for the weight of the robot to push into the foam tiles. Nothing else from the robot should touch the ground.

Something you can do is set the robot in CAD onto a field. Set up obstacles such as the crater and simulate driving over the crater by moving it across like you think it would in the real world.

If either of the plates intersect with the obstacle, add some more clearance so you don't get beached like a sad whale.

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Design Tradeoffs > Pushbot Mecanum, 6WD, Other Recommended Drivetrains

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Important: The pushbot drivetrain, commonly built by first-year teams using the FIRST®-provided guides, is not recommended as a competitive drivetrain.

We do recommend teams who have purchased the Tetrix kit to build it for educational purposes only - that is, to get familiarized with the parts and basic building principles using a channel-based kit. However, we do not advise that teams use that pushbot at a competition due to its many flaws.

The pushbot is powered by 2 motors, and as stated above, there isn't a reason to stay with 2 motors on drivetrain.
The pushbot has poor top speed and turning ability, given that the gear ratio (40:1 on 4 inch wheels) is half the speed that many teams use.
It is not advisable to use direct drive.

However, most if not all of these problems will be solved by using a four-motor drivetrain such as the ones recommended in the drivetrain guide (mecanum, 6WD, etc.). Therefore, it is recommended for teams to refer to the drivetrain section and see which drivetrain would fit best for their overall game strategy.

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Drivetrains > Drivetrain Options

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Omni Wheel — Omni(directional) wheels, sold by many different vendors, are a special type of wheel that prioritizes mobility and strafing (moving laterally) over traction or front-back movement. They are similar to mecanum wheels in that omni wheels have rubber rollers that rotate perpendicular to the plane of the wheel.

Thus, the robot can move sideways (although the robot is not powered in the sideways direction). It is also utilized as a low-friction wheel in 4 wheel, 6 wheel, and 8 wheel drivetrains instead of having corner traction wheels.

Furthermore, X-drive utilizes four omni wheels, though traction is at a minimum.

A mecanum wheel is technically an omnidirectional wheel, but when generally referred to, an "omni wheel" has rollers rotated 90 degrees to the rotation of the wheel, where a mecanum wheel is generally 45 degrees.

Traction wheel — A traction or grip wheel is a wheel designed for maximum grip. It has an outer ring made of rubber, and its wide track ensures a larger contact patch with the ground. Traction wheels are commonly found in tank drivetrains. They are sold in different sizes and thicknesses by different manufacturers.

Strafing — Strafing is the act of moving sideways or laterally (somewhat similar to drifting). It is possible with omni or mecanum wheels, and not possible with traction wheels.

Parallel Plate Drivetrain — A parallel plate drivetrain is a drivetrain that has drive pods that consist of 2 plates spread apart with wheels and drive transmission in between them.

These plates can be anywhere from 1" to 5" apart, depending on the space requirements of the wheels and drive system. Generally, a pod width of 3" or less is desired to maximize the space between the drive pods for mechanisms such as an intake.

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CAD Tutorials

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After learning your CAD program of choice, determine the necessary requirements for the drivetrain based on the current game. Teams should shoot for the wheelbase that works the best in that specific field's layout.

For instance, in Relic Recovery (2017-2018) a drivetrain required precision to not only grab glyphs from the center pit, but also to line up against the cryptobox. Thus, mecanum wheels and a wide center section of the robot proved an advantage over a 6 wheel tank drive. (However, it should be noted that with sufficient practice and competent drivers, any drive base can be competitive up to a certain extent).

After selecting a drivebase, determine the number of motors. Keep in mind the eight motor limit is a pain that shouldn't be ignored. A good rule of thumb is four motors for driving and four motors for the other mechanisms (e.g. intakes, linear slides, arm, etc.) For most modern FTC® games, you need minimum 7 motors to be highly competitive, although 8 is a good rule of thumb.

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Design Tradeoffs > 2 Motor Drivetrain 4 Motor Drivetrain

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Important: In general, it is not recommended for teams to use 2 motors on the drivetrain, but instead use 4. This is mainly due to the added power and increased acceleration 4 motors provide.

Typically, top speed is determined by the gear ratio and the motor specifications, not the number of motors. However, acceleration is affected by the number of motors, and as FTC® robots need to change direction and accelerate numerous times per match, slow acceleration has a significant adverse effect on the competitiveness of the robot. In addition, 2 motor robots may struggle to get over obstacles or climb up ramps, due to less power. One question that often comes up is "don't I need more motors for other things on the robot?" This is a valid question, but the answer is generally no. It is possible to build a competitive robot with 4 motors allocated to drivetrain, and 4 motors for other mechanisms, so there should be no reason to skimp. Do remember that the drivetrain is the foundation of the robot. Your mechanisms will not be anywhere near optimized if the drivetrain can't get your robot from A to B quickly and efficiently. There has not been a game in FTC history where the top robots needed >4 motors for the drivetrain, so this is a pretty safe rule to follow.

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Drivetrains > Drivetrain selection

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Warning: It is not recommended for teams to use spur gearboxes on their drivetrain. Instead, use planetary gearboxes, as they are less prone to shock loads and breakage.

Traction/Pushing Power: While this feature is often overemphasized, it is still very important. Pushing power describes a drivetrain's ability to endure defense/engage in defense. In addition, traction will be important if the drivetrain must traverse obstacles or some sort of terrain.

Many factors affect the pushing power of a drivetrain, including wheel type, motor gearing, and overall weight of the robot.

Note: If you already have a very agile drivetrain with experienced drivers, a team can avoid defense instead of having to fend it off or engage in it.

Powering the drivetrain: Generally, there are four options for power transmission: direct drive, chain, gear, and belt. More detail about each option can be found in the power transmission section.

Teams should stay away from direct drive, as gearboxes are prone to breaking, especially under shock loads (for example, if the wheel is hit by another robot, or the wheel slams into the wall).

We recommend belted drivetrains, but realize that belt is a difficult option for new teams. Chain and gears are also great options - chain requires a bit more forethought, as 1+ tensioner per side is required to maintain correct tension in the chain.

CAD or a detailed sketch is generally recommended with chain in order to visualize the chain run (where the chain will be placed). Gears are slightly simpler, and can be a fantastic and easy option, especially when using extrusion. We would advise to stay away from TETRIX gears, and use the gears from other kits such as the REV delrin gears (with hex hub strengthener) or REV aluminum gears.

See the /docs/common-mechanisms/power-transmission/index section for more details.

An important step is determining what you want out of your drivetrain.

Do you want speed?
Pushing power?
Ability to get over terrain?
Do you need to strafe?

All of these questions should be answered before choosing a drivetrain.

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3D Printing > 3D Printing Design Guide

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Here is a quick guide on designing 3D printed parts that we hope is helpful for teams who may be unfamiliar with 3D parts.

The first consideration when designing 3D printed parts is print orientation. This refers to the side that contacts the print bed. Preferably, the part should have a flat bottom to maximize contact with the print bed.

Tip: Maximizing contact with the print bed will make sure the part doesn't delaminate or warp from the bed and increase print quality.

If it is impossible for the part to have a flat side to print on, a simple solution is to split the part into multiple parts along a plane. For instance, the gearbox plate below didn't have a flat side to print on, so it was split in half. The part was later sandwiched with numerous screws and plastic glue. If this plate was printed as one part instead of split in half, support would have to be used to create all of the necessary holes. Parts that use no support material make sure that the least amount of plastic is wasted.

Tip: Don't chamfer or round anything on the perimeter of the first layer on the bottom face of the part. Chamfering or rounding will increase the chances of the part warping, especially on unheated print plates.

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Design Strategy > Competition Tips and Mistakes > Neglecting driver practice Constant driver training

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Important: A persistent problem with new teams is neglecting driver practice. Drive practice is to be done throughout the season, not the week before competition.

No matter how good your robot is, the robot is only 50% of the equation. The driver(s) are the other 50% which determine the success of the team as a whole. Even if your robot is the best in the world, an inferior robot with a competent drive team more than likely will beat your robot with a poor drive team. By April's world championships, most top teams have run hundreds of practice matches.

This gives some obvious advantages compared to a team with lesser practice.

#. The driver(s) are totally familiar with handling the robot in every situation. #. The robot is proven to be reliable enough to survive hours of operation. #. The immense data that teams gather from test runs are used to optimize every element of the robot.

Driver practice not only familiarizes the driver(s) with the robot and serves as a test of robot reliability, it also simulates in-game conditions. Learning to push the limits of your robot should be done during practice, not at a competition. This way, drivers will become more comfortable driving under stress and pressure. Teams with intensive driver practice will purposely make things more difficult (such as placing a disabled robot in the middle of the field or unplugging a drivetrain motor).

While this may seem extreme, it is really just a form of preparedness. If your driver doesn't know how to react, then you need more drive practice.

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Useful Resources > Mechanical Design and Build > Calculators

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ILITE Drivetrain Simulator (v2020) (https://www.chiefdelphi.com/t/ilite-drivetrain-simulator-v2020/369188) --- A drivetrain calculator that puts an emphasis on time to target. Input a target motor, number of motors, gearing, and a wide range of elements about the drive train and electrical system. The output shows estimated peak speed, estimated sprint time, minimum system voltage, and maximum voltage while the drive train is at full speed.

JuliaDesignCalc (https://www.chiefdelphi.com/uploads/short-url/uJyrWsJqE8OVqbvMLMnSgJ8QUdP.xlsx) --- A spreadsheet design calculator. However, it does not include FTC motor data, so you will need to add that manually using the data from the motor-data section.

Pulley Center-to-Center Calculator (https://sdp-si.com/tools/center-distance-designer.php) --- A fully featured belt pulley center-to-center distance calculator.

ReCalc (https://reca.lc/) --- A collaboration focused mechanical design calculator, currently in alpha, which provides sharable links.

Thad's EveryCalc (http://everycalc.thadhughes.xyz/) --- A mechanical design calculator which covers a wide variety of mechanisms, while also providing some utilities like belt sizing, a trajectory calculator, and more.

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CAD Tutorials > CAD Tutorial Part 3 - Custom Pulley Template

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When designing methods of power transmission, it's useful to have an adjustable pulley generator to rapidly rearrange C-C (center to center) distance for design changes. Typically, FTC teams use the HTD5 belt profile due to its deep tooth profile, which adds resistance to slipping and increases load capacity. This tutorial will focus on the HTD5 profile, but it is relatively easy to adapt for different profiles.

To make the pulley fully parametric (adjustable without redoing the base sketch), we will use Equations (in Solidworks and Creo), Parameters (Fusion 360 and Inventor) or Variables (Onshape). Equations allow a user to quickly adjust values and change multiple dimensions in a sketch or feature.

First, define a new variable "n" and set a default value of 24. This is crucial since "n" will affect the number of teeth, which will define the angle between teeth and the circular pattern.

Copy the sketch below.

The 15° equation is done by typing =360/"n" into the text box.
Note that 5mm dimension at the top describes arc length, which is done in Solidworks by first selecting the two points and the connecting arc.
The two big circles are tangent to the two smaller circles, but the two smaller circles are not tangent to each other.

Leave this sketch as a reference and use "Convert Entities" to create sketches for additional features.

Next, extrude the outer bold circle. Cut-extrude the profile in the reference sketch. Do these features separately.

Now, just create a Circular Pattern. Define Direction 1 as the top face and create "n" instances of the cut-extrude feature.

Now just sketch on the side plane and sketch the flanges. This is up to you, but I prefer to keep the outer point vertical to a point pierced through the outer circle. That way, the flange changes with respect to "n".

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Sample Drivetrains

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In this section, we compile several sample drivetrains which you can use as a starting point for your own designs. You should also check the gallery of robot designs in the Appendix.

goBILDA strafer chassis (https://www.gobilda.com/strafer-chassis-kit-v4/) Basic mecanum chassis by goBILDA. Simple and easy to build chassis, providing an excellent starting point for robots built from goBILDA parts. goBILDA BeeLine Chassis (https://www.gobilda.com/beeline-chassis-kit/) Basic 6 wheel drive chassis by goBILDA. Simple and easy to build chassis, providing an excellent starting point for robots built from goBILDA parts. Strafer chassis with Dead Wheels (https://drive.google.com/file/d/1R85u8nGGmBu5_6jIztOH3-5_W4XK08Mb/view?usp=drive_open) Modification of goBILDA chassis by FTC® 9794 Wizards.exe, which adds dead wheels. Also see their video tutorials: https://www.youtube.com/watch?v=OjNvAD350M4&list=PLICNg-rquurYgWAQGhu6iC0At75vgqFJp REV Robotics 6 wheel drivetrain (https://docs.revrobotics.com/duo-build/channel-drivetrain-build-guide) Sample 6 wheel drivetrain built using REV kit. AndyMark Tile Runner chassis (https://andymark.com/products/configurable-tilerunner-chassis-options) A universal chassis kit sold by AndyMark. It is available in several modifications: 6 wheel, mecanum, tank tread. It is expensive, but using provided 3d models as inspiration for your own drivetrain is free. Wizards.exe 6 wheel drive chassis (https://drive.google.com/file/d/1iu2UUNlqoQ6bS1vnoRPtUI0Uv3lLjNec/view?usp=drive_open) Another design by FTC 9794 Wizards.exe. Combines custom side panels with Actobotics parts (gears, chain sprockets). Custom drivetrain by FTC 14875 LightSpeed (https://drive.google.com/file/d/1iu2UUNlqoQ6bS1vnoRPtUI0Uv3lLjNec/view?usp=drive_open) This design uses goBILDA mecanum wheels, motors, and some channels combined with custom side plates. NX VANTAGE-H (https://cad.onshape.com/documents/3d22333d5ba0abcc62edb57e/w/fa027f644666441544a378c6/e/693039a92658a00632996b28) Another custom drivetrain using goBILDA mecanum wheels, by redditor /u/nateless. Note that this design can be viewed but not downloaded---this is intentional; see his original reddit post (https://www.reddit.com/r/FTC/comments/c8vlsj/cad_for_nx_vantageh_is_going_public/).

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