Ok Guys here it is, the long promised dual steering servo mod!!! First thing I want to say, contrary to popular beleif this is not my mod, I got this idea from PPman in france who had it posted on CEN's website. I just refined and perfected it!! LOL
The Genesis, Gst 7.7 and the Nemesis Monster Trucks require more than 280.oz of steering torque to be more responsive on the track and in the field. This mod is intended to be an inexpensive alternative to the more pricey but very suitable single Ultra Torque Servo Swap using a highend servo like the Hightec 333.oz HS5955MG. That Particular servo costs around $130.00 shipped, This mod can be done for about $30 using OEM parts that can be obtained from eBay.
Let's Gather Some Parts!!
Click on the links to see source of these parts
(1)[link=http://search.ebay.com/search/search.dll?from=R40&_trksid=m37&satitle=cen+servo&category0=]Additional OEM 144.oz CEN Servo[/link]
(1)[link=http://cgi.ebay.com/CEN-Genesis-Nemesis-GST-7-7-Linkage-and-Servo-Toppers_W0QQitemZ220133804530QQihZ012QQcategoryZ44 029QQssPageNameZWDVWQQrdZ1QQcmdZViewItem]OEM Servo Arm And Linkage[/link]
(1)[link=http://search.ebay.com/search/search.dll?from=R40&_trksid=m37&satitle=CEN+Genesis%2FNemesis%2FGST+7.7+Bellcrank% 2FSteering+Tie+Rods&category0=]Additional OEM Servosaver and Bellcrank Set[/link]
(1)[link=http://search.ebay.com/search/search.dll?from=R40&_trksid=m37&satitle=servo+y-splitter&category0=]Servo Y-Splitter Wire[/link]
You can use any Brand of Servos, Arms and Linkage, just be sure they are identical in Brand, Torque Rating, Speed, and Length of Arm, This is critical to the mechanics of this mod. You will see why later..
Time to Take Things Apart!!
First, you will need to remove the radio tray and front suspension assembly. I took the radio tray by removing the screws from the side plate, the front cross brace and from the top of the servo save/bellcrank. When you pull the tray up and out check that the linkage which is attached to the servo arm just snaps off of the ball stud. This will allow the radio tray to be removed as a single unit, as seen here
Now this should give you a good view of the steering linkage as it came from the factory
To remove the front suspension it is now as easy as removing the 6 chassis side plate screws that hold it in place.
Time to Install the Bellcrank and Linkage!!
This is the easy part, and fun!
You will only need a few parts from the bellcrank/servo saver kit you obtained earlier. First thing you need to do is reverse the servosaver/bellcrank so that the top bellcrank arm is on the opposite side of the servo saver. When you are done it shold look like a mirror image of the Bellcrank/servo saver assembly in the truck. remove the idler arm from the drag link and replace it with the new reversed bellcrank/servosaver assembly. It look like this when you are done!!!
Now you can reinstall the modified assembly back into the truck, in reverse of how you removed it. It should look like this, back in the truck!!!
We can now move on to the real fun, cutting and hacking!!
Modifying the Radio Tray!!
Strip the radio down to its core plastic part, including removing the receiver and battery covers.
Now, for the cutting as I promised. Your Dremel with a heavy duty abrasive wheel works best for this operation, but if you dont have one, the a hacksaw or other means of cutting will work, just not as clean. The first thing you will need to cut off is the sides of the battery box(We Will Relocate The Receiver Battery Pack to an Alternate Location, Discussed Later), Before your first cut, sure to carefully look at the pictures below, to reference where to cut and how much to cut. The pictures also show the rough cut out for clearance of the servo placement.
The new servo mount is made from .120" Aluminum plate you can get from any hardware store. You will need to cut 2 pieces, 1 to act as a shim for the Servo mount plate and the servo mount plate. Both plates need to sit down into the remainder of the battery tray that has been cut away. The Mount Shim does not have to fit the space as tight as the mount plate does. The mount plate will need to be cut to fit snugly in the tray area and two 1/8" mounting holes will need to be drilled thru both plates. The location of these holes is not critical. The more you space them out fromeach other the more stable the mount plate is. Using the plates as a template drill an .094" hole in the plastic and screw in 2, 3mm screws to hold all the parts together. Taking your time, cut the space required to mount the servo on the new plate and drill 4 holes using the .094" drill bit and the servo as a template for the holes.
With the plates installed the mounting surface should be approx. the same depth as the OEM servo location as seen here:
You may have noticed by now that I also cleaned off all the mounting stancions for the reverse servo. I dont use the reverse on this tranny because I have broke it too many times. But this mod will work with the stancions in place, if you decide you still want to use the reverse. I have seen people use a smaller servo for reverse as well as raise the standard servo using spacers on the stancions. I aslo, cut a new slot in the receiver box, to allow for the new servo wire to pass into the receiver compartment.
Let's Put It All Together Now!!
This is the fun part for me!! You should be able to put it all together, now. Be sure you mount the servo with the output gear at the sam end as the original servo, this way you can use the same length arms and linkages. It is very imprtant the arms and linkages are the same length, because if they are different you wll have binding in the motion of the servos, thats why is so important to use the same servos as well..
As you can see in the last 2 pics, the servos are mounted at the same height, that is why I use the spacer under the servo mount.
Finish assembling the radio tray with the remaining throttle servo and receiver. Using the y-spliter connect both servos to the same #1 channel plug on the receiver, Now is a good time to zip tie all loose wires to keep them under control and add just a touch of detail to your mod. I also, inserted the antenna at this stage.
Be sure both of the linkages are exactly the same length, this help reduce any binding in the steering mechanism. I use a digital caliper to be sure of the dimensions.
To be sure everything moves with no binding, complete your assembly, remove the servo arms from the servo and power up the system. Turn on your radio and be sure your trim is set to neutral. Turn your steering wheel completely to the left and then completely to the right. Being sure the servos have moved back to the nuetral postition reattach the arms in the most center postion. Once the arms are reattched and screwed down tightly, turn the wheels again looking for ANY binding, in fact you should feel about the same slop in the system as you did before you started this mod. That is to insure there is no binding. If you do feel that everything seems just abit tight then loosen or tighten one of the linkages to the bellcranks, until it seems just right.
I relocated my battery to the front of my shock tower, using 1/8" Aluminum and a couple l brackets I had in my junk fitting box. Works like a
Now For The Payoff, Go Play!!
Be sure the batteries are fully charged, the fuel tank is topped off, and go burn some fuel!!! Check the trim on your steering circuit so the truck tracks straight.. Now enjoy the added steering power!! If one servo burns or locks up your day is not completely over you still have one servo to get you home, to replace the burned servo it will only cost about $15..
[link=http://picasaweb.google.com/TheRealDogman/DualServoMod?authkey=uOfLcs9pHvM]Here is a link to my private library of pictures, feel free to browse if you need more pictures to help[/link]
If you have any questions feel free to ask..
Good Luck And Have Fun!!