> News

Building the S960 â€“ Tips & Tricks â€“ Part 3 (04/10/2005)

By:: Glenn M. Cauley
Linked to:: Serpent 960 1/8 scale 4WD

This article follows Parts 1 & 2 where I had focused on building the front and rear ends of the S960.

Part 3 focuses on building the center section of the S960, including the radioplate and electronics, and shock absorbers. I have previously written several other articles that will now come into play, so instead of rewriting those articles here, I will give you the links to them. I will also introduce a few more new tips & tricks. Again, for those who have shared their knowledge with me, I thank you!

For those of you who are new to this series of articles, I will again mention that you should take your time and carefully prepare all parts for assembly. The car will go together better and operate more smoothly. PATIENCE is the key here. Sure you can "slap it together" quickly and the result will most likely be very good, or you can take your time and the result will be exceptional!

Here are some items to have on hand, or have access to (note that some of these are already listed from Parts 1 & 2 of these articles):

• Mototool (Dremel™ or other)
• Grinding wheel with flat outer edge (for mototool)
• Small and medium sanding drums (for mototool)
• Cutoff disk (for mototool)
• Hobby knife with sharp blade (e.g., #11 blade)
• Small jewellers files (round and flat)
• Shock assembly stand
• Shock rod gripping tool
• Black marker with wide chisel tip
• Safety glasses & gloves
• Shock vacuum pump system (for bleeding shocks)
• Digital calipers
• Thin CA glue
• Shoo Goo™
• Motor spray
• Bearing oil
• Scotch-Brite™ scour pad (brown or green)
• Shop towels (paper towels)
• Fuel tubing
• Shrink wrap 3/16” diameter (for wires)
• Shrink wrap 1-3/4” diameter (for battery packs)
• Cotton swabs
• Misc. M3 screws, nylock nuts, and flat washers
• Misc. nylon spacers

Following the Previous Tips

Follow the various tips and procedures in Part 1 when assembling the radioplate and shock parts.

BALL-JOINT TUNING
When installing metal pivotballs in plastic ball-joints, make sure to install the pivotballs on the proper sides of the plastic ball-joints and that they rotate freely. The proper side of a ball-joint is the side with the circular moulding line around the hole.

GRAPHITE PART PREPARATION
Prepare and seal the edges of the following graphite parts:

• Chassis stiffeners
• Radioplate

THREADLOCK
Where indicated in the instruction manual, be sure to apply an appropriate amount of the threadlock; small amounts are usually better.

Use only “removable strength” threadlock such as Loctite 242® “blue-grade.” DO NOT use permanent threadlock such as Loctite 262® “red-grade.”

Rollover Bar

The chromed rollover bar can use a bit of attention, in the form of some grinding and also some padding at the top.

GRINDING SETSCREW FLATS
The ends of the rollover bar, where they insert into their holes in the radioplate bracket, do not have any flatspots for the setscrews to seat. It may be possible to pull out the rollover bar if the setscrews are not sufficiently tightened.

I remedied this situation by grinding small flatspots on the ends of the rollover bar where the setscrews tighten against. This allows the setscrews to have a much better grip on the rollover bar, and prevents the bar from being pulled out.

1. Insert the rollover bar all the way into the radioplate bracket.
2. Tighten the setscrews against the rollover bar.
3. Loosen the setscrews and remove the rollover bar.
The setscrews will leave small marks where they were tightened against the bar. Use a black marker to mark those spots on the bar ends.
4. Using a grinding wheel in a mototool, grind a flatspot on each bar where the setscrew marks are. Each flatspot should approximately 0.5mm deep and 4mm long.

ROLLBAR PADDING
I use a short piece of fuel tubing to cover the top of the rollover bar. This serves two purposes: it cushions the bar making carrying more comfortable, and also protects the bar in the event of a rollover.

1. Cut a 7cm piece of fuel tubing.
2. Put a drop or two of bearing oil in one end of the fuel tubing. This makes it easier to slide the fuel tubing over the rollover bar.
3. Push the fuel tubing onto one end of the rollover bar, and push it up and over the top of the bar as shown.

Receiver Battery

Here are a few things I did when installing the receiver battery.

CHAMFER SHARP EDGES OF MOUNTING PLATE
Use a file to remove the sharp edges of the battery cutouts in the mounting plate, so that the edges do not cut into the battery cells. Do not sand too much or the bottom of the batteries may drop below the mounting plate.

MOUNTING THE BATTERY PACK TO THE MOUNTING PLATE
Determine which way you want your battery to face so that the wire exits on the proper side and wires are not in danger of being damaged. Place the battery on the mounting plate, then add a seam of Shoo Goo around the battery where it meets the mounting plate. Allow to dry.

I then used two 0.75” wide pieces of 1.75” dia shrinkwrap (used for battery packs) to bind the battery pack to the mounting plate. Heat the shrinkwrap until tight (especially on the bottom).

Fuel Tank

FLASH REMOVAL
There was a bit of plastic flash on the fuel tank seam where the upper and lower halves are joined. Use the side of a hobby knife in a scraping motion to remove the flash. This will prevent the fuel tank from coming into contact with the sides of the radioplate cutout.

Do not use the sharp edge of the blade to cut away the flash (or a sanding drum in a mototool) as you risk cutting into the fuel tank body itself.

MOUNTING POST - ADDING A SLEEVE
When installing the fuel tank on the mounting posts, I noticed that there was a large amount of play between the tank and the post (even with the rubber collars installed). According to Serpent this is normal. However, I wanted to remove a bit of the play, so I installed a 4mm long piece of 3/16” shrinkwrap on the alum mounting post and heated it until it shrunk onto the post. Then I installed the rubber collar over the shrinkwrap and installed the fuel tank. The fit was a bit more snug while still having sufficient play.

MOUNTING POST - LOWERING THE HEIGHT
I lowered the fuel tank by 1mm by replacing the stock 5mm nylon spacers beneath the mounting posts with spacers of 4mm. There remained a ~1mm gap between the tank and the batteries.

If you try this trick, I recommend that you do not cut the stock spacers to a lower height, but rather find other spacers. That way if you end up lowering the tank too far, you can still go back to the original spacers.

Radioplate Assembly and Installation

Setting up the electronics in a gascar is probably my favourite thing to do. (Please note the sarcasm in the previous statement.) It requires a lot of planning and implementation, and can sometimes take a very long time to get everything done correctly.

With the layout of the S960 radioplate and having the choice of throttle servo mounting positions, this task was much easier (read: "less frustrating") than on other cars.

STEERING SERVO MOUNTING
Installing the steering servo was very easy and straight-forward. When I attached the steering servo mount to the radioplate, I noticed that the servo arm comes very close to the radioplate cutout. I used a mototool and sanding drum to remove a small amount of material from the radioplate cutout as shown. I then re-sealed the sanded area with CA glue applied with a cotton swab.

See the section "Steering Linkage" for more information about how I attached the steering linkage to the servo saver.

THROTTLE SERVO MOUNTING
The first big decision was how to mount the throttle servo… laydown or upright. I decided on the upright mounting position for a few reasons:

• simpler servo mounting
• servo less susceptible to damage from side hits
• one less turnbuckle linkage to worry about
• close proximity of receiver to all electronic components meant shorter wires and easier routing

When mounting the throttle servo, you should shorten the two front M3x16 screws to a length of 10mm. At full length, the screws will stick out below the plastic mounts. Since there will be a lot of wires in this area, you do not want to have wires rubbing against protruding screws. I use a mototool and cutting wheel to shorten the screws to a length of 10mm.

TRANSPONDER MOUNTING
I attached a Serpent 1666 Transponder Mount Graphite Star to the right underside of the radioplate, right above the steering servo. I had to drill two 3mm holes in the radioplate, then used some spare 3mm screws and nylock nuts to attach the mount.

If you don’t have this transponder mount, you can easily make one with a spare piece of 2.5mm graphite or fibreglass. Before you install the mounting plate, mock up the parts to ensure that you can attach the transponder to the mounting plate when the mounting plate is in position. I used Shoo Goo to attach my personal transponder to the top of the mounting plate.

KO PROPO ON/OFF SWITCH & MOUNT
I decided to install a KO Propo Electrical Switch in my S960 to go with the rest of the “high tech” theme of the car. For more information on this great switch, see my articles at:

http://www.mytsn.com/publ/publ.asp?pid=10078
http://www.mytsn.com/publ/publ.asp?pid=4463

To mount the switch, I used a homemade mounting plate which I describe in my article “Serpent 960 Switch Mount” at http://www.mytsn.com/publ/publ.asp?pid=11447

WIRE ROUTING – ‘GREASE’ ISN'T THE WORD... ‘TIDY’ IS THE WORD
When routing the wires, fold and route as neatly and cleanly as possible. Use cable ties to secure all wiring out of the way so it does not get damaged.

THROTTLE SERVO LINKAGE
After you install the throttle servo, it is a good time to prepare and check the throttle servo linkages. Mock up the linkages and servo arm to check that all parts operate properly without hitting anything. It is better to find out now than at the end of the build.

For ideas on setting up linkages, see my article “Building Carb/Brake Linkages” at: http://www.mytsn.com/publ/publ.asp?pid=9742

Steering Linkage

When I connected the servo arm to the servo saver using the steering linkage, I deviated slightly from the S960 instructions. The instruction manual indicates to attach the steering linkage (the turnbuckle between the servo and the servo saver) to the BOTTOM of the servo saver arm. This puts the linkage at a very steep angle.

I decided to attach the linkage to the TOP of the servo saver arm; this makes the linkage much more horizontal and parallel to the plane in which it travels.

There is just enough room below the radioplate so that the lnkage can move without hitting the underside of the radioplate. However, I had to sand away a small amount of material from the front right bulkhead. Using a mototool and sanding drum, I remove approximately 2mm of material along the 'arc cutout' in the bulkhead as shown; this is to prevent the linkage ball-joint from hitting the bulkhead. Be careful to remove the least amount of material possible so the ball-joint will not hit the bulkhead in its motion.

The final touch was to space the ball away from the servo arm by 4mm. I had to replace the standard M3x6 screw with an M3x10 screw.

When finished, the steering linkage is much less angled. No parts seem to hit or interfere, and the range of motion seems unimpeded.

Rear Bodymount Center Guide

With the installation of the rear shocks, I found that the read bodymount center guide hit the rear shock upper mounts when the suspension is fully downward.

Use a mototool and small sanding drum to remove excess material from the indicated sides of the center guide. Remove only enough material to clear the shock upper mounts.

Front Bumper and Bodyposts

Before installing the front bumper, dab a small amount of Shoo Goo around the edge of the M4 nylock nut, then install it in its cavity in the front bumper. This will ensure that the nut does not fall out of the bumper when you remove it.

The front bodyplate has two oval channels where the front bodyposts attach, allowing you to move the bodyposts forward-and-back. Make sure you install both front bodyposts in the same position.

Shock Absorbers

Along with installing the electronics, building shocks used to be one of my least favourite tasks. That is until the release of Serpent’s new RCC shocks. These shocks are much easier to build (since they are already pre-built for you already - thank you, Serpent), and function much more smoothly than previous Serpent shocks.

SHOCK ASSEMBLY
Assemble all four shocks as follows:

1. Unthread the shock insert from the bottom of the shock body.

2. Clean out the shock body with motor spray and a paper towel.

3. Pour shock oil onto the foam on each plastic insert and spread the oil onto the foam. Repeat as necessary until the foam is saturated with oil. This will help to eliminate air bubbles that may otherwise enter the shock.

4. Invert the shock body and fill SLOWLY with shock oil until the oil reaches the 2nd top thread.

5. Place the shock body in a vacuum pump shock bleeder to remove air bubbles from the shock oil. (Austin Powers pump… Yea baby!)

6. Place the bled shock bodies inverted in a shock assembly stand.

7. Pull the shockrod out all the way of the plastic insert.

8. Insert the shock piston into the shock body, and thread in the plastic insert by 1-1/2 turns. BE CAREFUL not to cross-thread the plastic insert!

9. Push the shock rod so the piston goes 1/2 way into the shock body. Oil will come out the shock body bleed channels.

10. Carefully thread the plastic insert all the way into the shock body. DO NOT overtighten or you may strip the threads.

11. Check the shock operation by slowly and smoothly moving the shockrod in and out. The operation should be smooth without any "gurgling" by air bubbles. After you fully compress the shockrod, it should rebound approximately 1/2 way when released.

SHOCK LENGTH ADJUSTMENT
Make sure the shock top nut is tight.

Adjust the length of the shock by using the plastic ball-joint at the bottom of the shockrod. Be careful not to damage the shockrod when you grip it; use either a tool specifically designed for gripping a shock rod, or use a pair of side cutters.

Completed Middle Section

Here is a view of the (partially) completed middle section showing most of the components in place.

In Part 4 of this article I will write about the gearbox and Centax clutch, including more tips and tricks and/or anything noteworthy about the assembly.

Stay tuned!

IMPORTANT NOTE!

When you are using hand tools and power tools (drill press or mototool), you MUST exercise extreme caution, and use proper protective eyewear and gloves. NO loose clothing around power tools, either! It only takes a momentary lapse in concentration to receive an injury or damage a part.