Chassis Guide - Your Home for RC Drifting

This guide will help outline the basics of RC Drift & help to explain the different chassis options.

This guide is meant for beginners to get the basic understanding, and then develop your own style. So nothing here is absolute. The great thing about the hobby is that we all have different personalities that transfer to our driving style. It’s the “soul” of our chassis; and its a reflection of the driver. Our pride, skill, and money go into that chassis; it’s not the chassis drifting itself, it’s YOU drifting the chassis. Ok…enough with the philosophy.

Understanding your chassis

What chassis is good for drifting?: Belt vs. Shaft
Ahh..the age old battle between the 2 types. Like I said, I’m not going to say what brand is better because everyone is different. But here are some typical chassis’ that people start out with:

Tamiya TT01

Team Magic E4D

HPI Sprint 2

Hot Bodies Cyclone

There’s also “RTR” kits, or “ready-to-run”. These kits come pre-built with almost everything you need to get started. While these are popular, you should really learn how to build a chassis from the ground up. You’ll have a better understanding of things if something goes wrong. Also may RTR kits like the TT01 doesn’t come with ball bearings. Those make a pretty big difference. If you’re on a budget, try getting a used chassis. There’s lots of guys selling gear online at good prices.

Now, belt vs. shaft? Which is better? This really depends on what you want out of a chassis. Here are the advantages and disadvantages of both:

Belt Driven

Pros

smoother acceleration on throttle
no torque steer (explained below)
less drivetrain loss since the transmission tends to be lighter

Cons

belts stretch over time, requiring tensioners or replacement
pulleys are often not enclosed and subject to debris flying in and shredding belts
belts stretch a little on initial throttle, so there’s less punch…its kinda like turbo lag…lol. But this is something that is always being contested, and there are belt upgrades that resist stretching (eg Tamiya Aramid Belts).

Shaft Driven

Pros

power is immediate the minute you hit the throttle
differentials more resistant to debris since diffs are usually enclosed, shaft lasts longer (assuming you’re using an aluminum upgrade)
no need for tensioners, not subject to skipping like belt pulleys, and easier to maintain

Cons

Torque steer. The biggest con of a shaft car
Limited gearing options. Chassis’ like the TT01 only have 3 different spur gears you can use.
if a rock flys into the area where the shaft is, you run the risk of locking the shaft and possibly damaging the motor, diff, etc. The TT01 and TB03 are suseptible to this, but it’s very rare. At least with belts, the worst happening is that the belt or pulley shreds, and comes off.

What is Torque Steer?

Torque steer occurs in all shaft driven chassis’ due to the layout of the drivetrain in relation to the motor and pinion. Without getting too technical, since the rotation of the drive shaft is perpendicular to the wheels of the car, the rotational force (torque) delivered from the motor has to change direction several times before it gets to the wheels. This causes the chassis to have the tendency to slightly “steer” itself and favor one side. If you have a shaft driven car, set it down and floor it without steering. You’ll notice that the car will eventually start to drift to one side automatically, or you can tell that it’s easier to drift one way compared to the other.

Belt driven cars do not suffer from this because the drivetrain is inline with the wheels. The pulleys are parallel with the wheels and motor rotation. Torque is delivered evenly and in the same direction (front to back), and only needs to change direction once (at the pinion and spur).

It’s possible to reduce torque steer by adjusting your setup. Most of us just live with it since it’s not that big a deal unless the torque steer is really bad (usually with big motors).

Differentials

Locking the rear diff. This should be the first thing that you do when you start your build. Depending on what type of rear diff you have, there are several methods. Many companies sell something called a “spool”, which is a solid axle. The point being is that you want both rear wheels to spin at the same time with the same power when you drift. This prevents the chassis from whipping out so much and doing donuts. Here are common ways of locking different types of rear differentials:

Planetary Gear Diff

open up the gear box. No need to remove all the gears…just pop the top off.
stuff the inside with something to prevent the planetary gears from spinning. You can use nitro flex tubing, hot glue, blue tac, esc wires, etc etc etc). As long as both wheels move when you rotate one wheel, you’re set. You can also use superglue, but be careful. You never know when you’ll need to take it apart.
Put diff back together and re-seat in the chassis.

Ball Diff

1. Remove the ball bearings, and put it back together, screw it down tight. Note that this works for a lot of people, but in my experience you risk shredding the pulley and diff cups (if they’re plastic). Never superglue the diff together (i’ve seen it happen believe it or not) unless you don’t care about buying pulleys or cups.

2. Remove metal balls and put electrical tape on the diff plates (the metal rings that go against the ball bearings) so that the tape side is facing the pulley. For me, this worked very well. It came from one of the guys on DRC. You basically put electrical tape on the face of the diff plates, and carefully cut out the inside and outside parts so that the face has tape on it. The tutorial also said to superglue the plate to the diff cup, but it works without it. Put it back together (without ball bearings) and tighten. The tape creates a tacky cushion that molds to the holes in the pulley or bevel gear.

3. Last method isn’t really locking but close. Just tighten the ball diff as much as you can. The drawback to this is that after while, the diff screw backs out and loosens. A drop of threadlock on the nut prior to tightening will help this. Just be careful not to get any glue on the pulley or ball bearings.

Different Types of Front Differentials

There are 3 main types of front diffs that you can use:

Ball diff. “Open” ball fronts (meaning that the diff is tightened to spec and not too loose) work well on wide sweeps and flowing tracks, but on narrower, technical tracks it sometimes has a harder time under low speeds. A front ball diff is one of the more popular choices for drifting.

Locked Just like the name implies. The front is locked similar to the rear. Not very common. My experience with locked front and rear is that you have to work the car in technical areas.

One-way. The dreaded front one way (my weapon of choice). One-ways use a special bearing that lets the wheels spin freely in one direction and lock in the other. This is one of the more difficult diffs to master since the minute you let off the throttle and turn, the one way bearing will react and lock one of the wheels up. For this reason, people call the one way twitchy and unpredictable. On large wide tracks, holding a drift with a one way can be tough since it can make the chassis “tail-happy” (as Wes from Stockton would put it). Front one-ways are pretty aggressive, and drivers that use them tend to attack corners a lot and eat tech tracks for breakfast.

So why use it? The biggest advantage is that one-ways act like an e-brake. If you know how to use it, you can re-pitch the car mid-drift to match your opponents angle without having to mash on the throttle (good when you’re up close to a leader and need to adjust without hitting). It also makes it easier in tight technical tracks that have quick switchbacks. A one-way is not for everyone. It takes a lot of smooth throttle control and a good understanding of the dynamics of your chassis. But if you can get the hang of it, there are plenty of advantages that make it worth it on the track.

There’s also a center one-way unit. Somewhat similar to the front one-way, but less direct since the one way bearing is at the shaft or center pulley, and not the front differential. Running a front ball diff with a center-one way is common. You get the e-brake feature of the one-way, but the effect is not as dramatic. Some people have tried to use both front and center, but it’s a bit much. It’s like cranking the brakes to 120% on the ESC. So in the words of Maverick from “Top Gun”: “I’m going to hit the brakes and he’ll fly right by….”.

Basic Upgrades: What’s the bare minimum I need to drift?

Technically, all you need is a chassis with a locked rear diff. While upgrades are great, you don’t necessarily need a ton of aluminum build a solid drift car, although in some cases, it makes things easier. Here’s a basic list of some good upgrades to get:

Belt driven chassis’

upgraded belts (like the aramid belts from tamiya) that resist stretching
aluminum steering set and rack
ball differential (if running a planetary setup) or one-way
ball bearings. most non-RTR kits come with bearings.
CVD’s (constant velocity driveshafts..bet you didn’t know that..lol..explained below)
adjustable shocks

Shaft driven chassis’

upgraded aluminum shaft.
pretty much the same as above with the exception of belts.

What are “CVD’s”?

CVD’s replace the “dogbones” that fit between the differential cups and the the outer drive cups at the wheels. Unlike dogbones, the outer drive cups are connected to the dogbone on a CVD unit. This prevents the dogbone from slipping out (especially in the front when turning) and provides a better transfer of power from the differential to the wheels. Those who have lost or thrown a dogbone know that it’s a good thing to get, and makes life much easier when taking things apart.The only drawback it that the nut holding the drive cup to the dogbone can come loose, shredding your wheel hub. So be sure to add a little thread lock to keep it in.

Source: dj722@hyperdrift