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Step by Step How to Install DNA Crawler Dig for AX10
By Tony Arnold - StampedeProject.com

Cue the music from Shaft... Who's can save your backside during an approach? DIG.  Who can slow your slide on a slippery slope? DIG.  Who can spin you around like no other ride? DIG.  Well if dig had a theme some, that... for better or worse would be it.  

WHAT IS IT
"Dig" is a drivetrain engineering feat only occurring in rock crawling.  Typical front "Dig", for the industry dominating AX10 shaft drive based crawler chassis, allows the rear driveshaft to be "shifted" remotely via a third-channel servo control from standard 4WD (4-wheel drive) mode, FWD (front wheel drive) with rear wheels in neutral, to FWD with the rear wheels locked/braked.  Sure, Venom, Losi, and Kyosho all now offer Dig options for their crawlers, however it is all the same principle and from an education perspective, it's easiest to start with the industry standard AX10 dig setup in this article.  

Historically, Digs were fabricated contraptions however DNA RC is the originator of the direct AX10 bolt up Dig unit and is one of THE upgrades for competitors.  Over the last two years DNA has continued to refine the unit to improve strength and ease setup.  DNA's newest Dig release features a blue anodized billet machined aluminum housing with all steel drive gears, metal shifting fork, and upgraded steel driveshaft outputs for improved strength.   Just to show the flexibility and provide a couple perspectives, I will show two Dig installs, one on a nearly bone stock Axial ARTR and one on DNA's own bolt on AX10 competition chassis.  

WHY YOU NEED IT
What will all these amazing transmission acrobatics do? Basically two things, controlling power delivery during crawling and allow tight pivoting turns.  

4WD of course provides the most forward thrust in most conditions. FWD (Front Wheel Drive) only with the rear drive in neutral allows the front wheels to grab traction and pull the car upward and over vertical climbs without the rear drive shoving the truck off an approach line or flipping the truck.  Oddly enough FWD can pull a rig over vertical obstacles that could not be cleared with a 4WD only rig.  Many drivers also use FWD to search for front wheel traction and then click into 4WD once front traction is found.  

Probably the coolest Dig trick is locking the rear driveshaft and turning full clock right or left  and blipping the throttle to turn.  The rear holds more or less and the front "digs" in to pull the truck around. Kind of like nailing one foot to the ground and running with the other - you're going to turn fast. With the rear wheels locked, the crawler literally pivots on its rear axle for near pivoting turns. This is a handy feature when you get bumped off your line or the gates require a hard turn without having to take reverse penalty points.  Other benefits of rear lock/brake is to settle the chassis and controlling descents - the FWD slowly pulls your rig forward and downward and the rear just drags along to control descent.  

DIG INSTALL
Installing the DNA dig is very simple. 

1.       Disassemble the transmission and remove the stock driveshaft outputs from the lower gear and replace them with the steel DNA outputs.

2.       Reassemble the transmission with the DNA Dig gears installed as shown using the longer included 3mm machine screws to secure the casing to the transmission.  

3.       Re-install slipper clutch and motor as normal.

4.   Shorten the rear driveshaft about an inch to allow for the movement of the dig shifting and allow for the new shorter driveshaft length requirements. 

5.       Install the transmission in reverse orientation from stock with the motor to the rear.

TRANSMITTER REQUIREMENTS
Being a Prototype Version 1 DNA Dig owner, the first version wasn't the smoothest and it did take some servo and transmitter tuning to get the servo and Dig engagement points right.  A tip from this experience is to hook up everything an assure the motor, dig, and servo shifting works correctly before installation back into the chassis. Now through precision machining, DNA's Dig operation is very smooth and if you own a 3-channel system with a 3-position third channel switch and EPA adjustments, life is easy.  With three dig positions 4WD, FWD/Neutral, and 4WD/Lock you need a three-position 3^rd channel switch on your RX. The highly programmable Spektrum DX3R is the obvious and easy choice. Sadly it's also one of only a very few transmitters transmitters including the Futaba 4K than have the needed third channel EPA adjustment and 3-position switch required to operate a dig.  From a transmitter setup perspective, simply install the Dig, mount the servo, set the center rear "neutral" point on the dig as the servo center, then adjust each end point with the transmitter's third channel EPA settings, and go crawling... all pretty simple stuff.  

If you are like me and don't have a DX3R OR are not willing to shell out big bucks for a premium transmitter? I and many crawlers have done easy modifications to Traxxas TQ-3 and old model Spektrum DX3 transmitters.  I did the TQ3 modification for our ARTR Dig and involved simply removing the third channel switch and popping out the spring and reinstalling the switch, viola a three position (but floppy) switch. Not using EPAs is hard on servos so make sure you use a $20 ServoCity Servo Extender for setting of mid, and end points.  The Spektrum DX3 modification requires some online auction searching for the retired old version DX3 (noting the DX3.0 will not work) and wiring in a Radio Shack three position switch in parallel to the existing third channel switch wires.  Seriously, if you can solder, it is very easy ... but details of those modifications are other articles.  I used my previously hacked DX3 to run the DNA Slingshot crawler and it works flawlessly. Just a note warranties are obviously voided with RX modification.

Spektrum DX3 Third Channel Modification

SERVO MOUNTING
Servo mounting previously involved fabricating some sort of servo mount, however DNA's groundbreaking design now includes a universal servo mount plate and linkage that works equally well with stock and custom AX10 chassis and with mini or standard sized servos. For our ARTR we mounted up the Hitec HS-645MG to the DNA servo mount via spare Axial spacers.  The plate bolts directly to the DNA dig unit and provides a sturdy mount for any servo. From experience I can tell you a 80oz/in+ servo works best.

I usually recommend a standard servo for increased durability, however high torque metal mini servos such as mighty mini Hitec HS-225MG can take the typical abuse. I installed the HS-225MG in the integrated dig shift servo mount in DNA's competition ruling black Delrin Slingshot SE chassis.  The included DNA dig mount is and dig unit are flexible enough for almost any aftermarket crawler chassis.  Look for the DNA Dig installed on a variety of chassis in future articles.

SOURCES: DNA Engineering - www.DNA-RC.com, Axial - www.AxialRacing.com, Tekin - www.TeamTekin.com, Hitec - www.HitecRCD.com, MaxAmps - www.MaxAmps.com