closer look

Yokomo

DRB

by R&D Japan

The DRB is Yokomo's first pro-drift-chassis with belt-drive. It is a highly capable drift machine which offers lots of setup options and parts to fine-tune it to the driver's needs.
Out of the box it is a standard 50/50 drifter. It can be easily changed to a counter-steer drift-machine with optional gear and belt packs (counter steer ratios: 1.3, 1.5, 1.8 and 2.0). Of course other optional parts for counter steer like front one-ways and c-hubs with high caster-angle are available, too.
Many parts of Yokomo's touring car BD5 are compatible with the DRB.

Like always I recommend to use thread lock on screws which go into aluminium parts. Be careful though! The thread lock should not go into bearings or moving parts.

Step 1

The build starts with the battery tray mounted on the chassis plate. The battery will be kept in place by two large rubber o-rings later. A simple and effective system.
The inner suspension mounts on front and rear are made of aluminium. Take care you don't mistake them. The one for the front is marked "FR", the one for the rear "RF".
Also the lower bulkhead halfes and the upper bridge support are mounted.

Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan

Step 2

The 48dp 77T spur gear is sandwiched between the two parts of the spur gear holder; a really nicely shaped aluminium part. The maximum size of spur gear you can use is a 81T gear. It might touch the chassis plate if chassis twist is too high , though.
Pay attention the the direction of the main gear shaft when assembling.
Next the three belt pulleys are installed. The two gears with 15T go on the main gear shaft, while the one with 12T is in the top position, helping the belt to clear the motor.
The small shims next to the pulleys/bearings have a smooth and sharp side. I let the smooth side face the bearings.
The whole motor mount block goes on the chassis. Don't forget to weave in the belts before you screw it on.

Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan

Step 3

The front uses a ball diff, on the rear a solid axle does its job. Both gears have 40T. The solid axle has plastic outdrives; aluminium rings keep it from splitting.
The diff uses 12 diff balls. Spring and thrust bearing are on one side and nut on the other. The outdrives are aluminium. Blades will be used on the universal drive shafts.
Belt tension can be adjusted by the excenters on the outdrives. The excenters have small indentations. A small ball on the lower bulkheads is pushed by a spring into one of the indentations.
If you want to change belt tension, just loosen the four screws of the upper bulkheads a bit (3/4 of a turn should be enough). With a screw driver which fits into the slits of the excenters, they can be turned until they click into the next position. Left and right side have to have the same position.

Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan

Step 4

The steering system is nicely done on the DRB. It is perfect for counter steering with its big max steering angle.
It is good practice to let the the left-handed thread of the turnbuckles all face left. This way it is easier to adjust settings later.

Yokomo DRB at R&D Japan

Step 5

The upper deck has a belt tensioner built-in. Please note that the long side of the belt tensioner bolt faces the tensioner roll.
Belt tension for the rear belt should first be adjusted with the excenters; fine adjustment is done by the tensioner on the upper deck.
Everything -including the upper bridge- is screwed on the chassis. Take care you don't generate any chassis twist when mounting the parts. The holes should line-up and no force should be needed to make them inline.
The upper bridge offers to adjust some chassis-roll if you use one screw in the center instead of two in the outer holes.

Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan

Step 6

The damper stays are of course also made of carbon. The front has seven holes for damper angle adjustment, the rear six. On the upper suspension arms the roll center can be adjusted by spacers.

Step 7

The DRB uses universal drive shafts. They are already assembled. On the front blades are used to avoid that the aluminium outdrives get any damage. The manual recommends the use of grease on the universals. If the space you drive on is dusty, I do not recommend the use of grease. It just acts as a dirt magnet.
The c-hubs for left and right side are marked with an "L" or "R", respectively.
The front dog bones are 45.5mm long, the rear ones 44.0mm.
The setting screw for downstop on the lower suspension arm should be 2mm on the bottom side as an initial set-up.
The suspension goes on the chassis. The rear suspension mount has a toe-in of 3.5° if used with the standard RF suspension mount.
The wheel base on the front can be adjusted by 1mm, on the rear 4mm are possible.

Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan

Step 8

The dampers are the usual Yokomo construction: one o-ring with spacer on the bottom and a two-part damper head. The body is threaded for fine adjustment. On the front pink springs with #450 oil is used, on the rear black springs with #350 oil. Oil is included in the kit.
The spring caps are made of aluminium for ultra responsive damper reaction.
The overall damper length should be 62mm.

Yokomo DRB at R&D Japan

Step 9

The kit also contains servo saver, alu pinion gear with 33T, body mounts, black antenna tube and urethane bumper. Those are not shown on the photos.
The battery should not be higher than 35mm; otherwise it will not fit under the upper deck. This is a usual height for lipo batteries, though.

Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan Yokomo DRB at R&D Japan

Basic Setup (Out of Box)

Front Toe-in on Suspension Mount
Rear Toe-in on Suspension Mount 3.5°
Rear Toe-in on Hub Carrier
Internal Gear Ratio 1:2.67 (40T to 15T)
Gear ratio with Included Pinion and Spur 1:6.22
Rear Lower Damper Position* 39.5mm
Caster on C-Hub
Bulkhead Cap Width narrow
Damper Spring Front/Rear 1.5mm wire, 6.5 windings, 25.5mm long (pink)/
1.4mm wire, 6 windings, 25.5mm long (black)
* The exploded drawing says, that part Yokomo Suspension Arm Rear (BD-008R) is used. The kit I used on this Closer Look-article contained part Yokomo Rear Suspension Arm Graphite (39.5mm) (BD-008RG1).

You can download the gear ratio tables from Yokomo's site:
for normal, counter steer 1.3 and counter steer 1.5
for normal, counter steer 1.8 and counter steer 2.0

Recommended for Counter-Steer

The minimum of parts recommended for a basic counter-steer setup.
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