Welcome to the world of Monster Trucks in HO. scale. The following is a basic guide for building an HO. scale Monster, but keep in mind that these are only guidelines... not law. Out of 30+ Monster Trucks we have at Greenbrier Raceway, no two are alike.

    Following are the sum of the best tech's and tricks we feel  will help in getting your first Monster Truck together with the least amount of problems. Before starting, please read everything in this article FIRST! While most steps are in order, familiarizing yourself with all steps can make the difference between crushing HO. vehicles with your Monster Truck, or crushing the truck itself and throwing it in the trash!

    To build your Monster, since the frame and hardware are made of brass, a slight working knowledge in the use of brass and solder is required. Basic tools required include a solder gun, a hobby motor tool (Dermal), a standard home drill, drill sizes from 1/16" to 7/64", and a pin vise.

Supplies:

Brass:
1/32" Diameter Rod
1/16" Diameter Round Tube
3/32" Diameter Round Tube
1/8"   Diameter Round Tube
1/16" Diameter Square Tube
3/32" Diameter Square Tube
1/8"   Diameter Square Tube
One pack assorted shim brass sheets (.002" to .010")

Gears:
2 Brass idle gears from T-Jet (3/32" center hole)
1 Brass top / rear gear from T-Jet (Same as above except with a 1/16" center
   hole)
1 Plastic cluster gear from A/FX gear plate
1 Plastic motor pinion gear (6 or 7 tooth) from any G+, HP-2, HP-7, etc..
1 1/4-20 Brass bolt (for making worm gears)

Motor:
Any one piece "can" H.O. motor with Brass or Steel casing (TycoPro, HP-2, HP-7, etc... NOT TOMY A/FX)

Tires:
Any 1" to 1 1/8" high wheels & tires of rubber from any toy

Body:
Any H.O. (1/64 to 1/87) scale body.
    Though obvious, the reason the body is listed in "Supplies" is that unlike other H.O. vehicles where the chassis is done and a body is fitted, H.O. Monster Truck frames are built around the body. Another point to consider here is plastic v.s. metal (cast) bodies. Plastic bodies are easy to work with and paint, but cast metal bodies are heavier ... and you will need weight.
 

ROLLING CHASSIS:

1.    Start by soldering the main chassis frame (Dia. 1) to fit body from 1/8" SQUARE brass tube. Body should just rest on the frame, with the frame just covered by body running boards. (if needed, body support posts may be soldered on top corners of frame) If Possible, frame should be wide enough to fit motor between inside side rails, but never should frame be narrow enough that motor extends past outer most sides of frame.

2.    With the body on the frame, mark wheelbase. Remove body and solder on support "legs" at wheelbase marks using 1/8" SQUARE brass tubes at least 3/4" long. Measure radius of tires to be used and cut legs to this distance. Square frame up (legs all same length) and check levelness.

3.    Solder 1/8" ROUND brass tubes first across the front "legs," then the rear. Check on flat surface for squareness again. Reheat and adjust as needed (Dia. 2). DO NOT add support rods at this point.

4.    Next, prepare tires as shown in Dia. 3. Drill center hole of each tire (wheel) to 7/64". Tap in 3/32" SQUARE brass tube insert into wheel and cut flush with wheel back.
    The reason for the 3/32" insert in the wheels is you will be using a 1/16" SQUARE brass tube for the axle. This will avoid any gear slippage. You will also notice when placing the 1/16" SQUARE axle into the 1/8" round axle housing -Step 3- there is a bit of 'slop'. This is an added plus, whereas this movement will give a slight suspension look while crushing cars. And with the front to rear movement, you will also get the illusion of "Crab" Steering (You did know Monster Trucks steer from the rear as well as the front didn't you?)

5.    Cut two axles from 1/16" SQUARE brass tube making sure axles are long enough to go through both wheels and axle housing. To hold on wheels, install a bent #20 flat head straight pin by pushing the pin into the axle ends. With body and wheels on frame, give the truck a small push across a smooth, flat surface (floor) to check how true the body travels. Be on the watch for the truck to turn, or if the truck runs straight, the body to travel sideways (sidewinder). Re-heat the solder joints to the axle housing, at the bottom of the "legs", and adjust as needed.

6.    Once truck is rolling true, solder on leg supports of 1/32" rod from the center of the frame to the bottom of the axle housings, just under the legs. (Dia. 2) NOTE: If the frame is not wide enough for motor to fit between frame sides (see Step 1) be sure to mount the support rods on the OUTSIDE of the frame, for you will be grinding the inner walls later to fit motor.
 

MOTOR & GEARS:

    You are now ready to install the axle gears, assemble and mount the drive shaft unit, assemble and mount the step-down gear assembly to the motor, and finally, install the motor... IN THAT ORDER.

1.    Prepare the Axle Gears (2 BRASS idle gears from T-jet with 3/32" center hole) with a 3/32" SQUARE brass insert as you did the wheels. Drill out center hole to 7/64" and tap in a 3/32" SQUARE brass insert. Solder insert in place and cut  'almost' flush with both sides of the gear(s).

2.    On both axle housings, centered between the fame "legs," cut a slot JUST wide enough to slip axle gear between halves. Hold the axle gear(s) in place between the axle housings and re-install the axle through housing AND gear. (Dia. 4)

3.    The most difficult step of building your Monster will be making the two worm gears needed for the drive shaft. You must drill a 1/16" hole through the center of the 1/4" brass bolt... and it must be PERFECT.

    A. Remove the bolt head.

    B. Chuck the BOLT in a hand drill (use a vari-speed power drill if possible).

    C. Chuck a good quality 1/16" drill bit in a hand held pin vise or clamp.

    D. As the bolt turns, center the drill bit to the end of the bolt and push
         lightly.

    If any wobble is felt in the hand held vise, chances are your not centered correctly, and you must start again. WORK SLOWLY!!! This will take practice to get right. A quick check of the worm gear can be made by once cutting the gear to approximately 3/8" long, slid gear onto apiece of 1/16" ROUND brass tube. Holding the tube, roll the gear across a slightly rough, flat surface (book) and check (or feel) for any wobble.You will need two gears approximately 3/8" long.

4.     Assemble Drive Shaft unit as shown (Dia. 5) using the two worm gears, drive shaft gear (BRASS top-rear gear from T-Jet with 1/16" center hole), drive shaft (1/16" ROUND brass tube), drive shaft sleeve (3/32" ROUND brass tube), and two drive shaft cross mounting supports (1/32" brass rod).
    All parts are to be soldered together, except the drive shaft sleeve,  whereas the drive shaft and gears must turn freely inside the sleeve.
    While assembling, trial fit drive shaft often across the axle gears mounted on the frame. The distance between the worm gears should be that to center the worm gears over the axle gears.

5.    Install drive shaft unit to frame by soldering the drive shaft cross mount supports to any spot of the frame leg supports (Dia. 4). Drive shaft cross supports may be bent anyway needed to mount properly.

6.    Assemble step-down gear and mounting unit to motor as shown (Dia. 6) using two step-down gear mounting supports (1/32" brass rod), step-down gear mounting tube (1/16" ROUND brass tube), and step-down gear (PLASTIC cluster gear from A/FX gear plate). Solder all brass parts in place on motor and slip on step-down gear.  (Note "Tips & Updates" link at bottom of page)

7.    Install motor with step-down gear into frame as show (Dia. 7) using a small 'tap' of solder at "X's" marked on motor in figure. If needed, file or grind inner frame so motor can fit between the frame rails. Be sure motor brush barrels DO NOT touch frame.
    Spin motor by HAND to check for binding of gears. Adjust as needed.
 

PICK-UP SYSTEM:

    The heart of any H.O. Monster Truck is its pick-up system. At Greenbrier Raceway, we now have over 30 Monsters of all different styles and configurations. However, all our trucks (and even a few pullers) operate on the same pick-up system. Though the system is quite simple to build and adjust. I found it a bit difficult to explain, so please refer to the diagrams often.

1.     Remove REAR axle and axle gear. Cut out ALL axle housing BETWEEN the REAR "legs" (Dia. 8).

2.     Assemble pick-up arm and assembly as shown (Dia. 9) to fit REAR axle area (Dia. 10) using all 1/16" ROUND brass except for the axle mounting tube... which is 1/8" ROUND brass tube.

3.     Fit assembly into frame (Dia. 10) and note where the worm gear centers over the assemblies axle mounting tube. Cut this section out as did the axle housing before. Assemble complete unit by sliding axle through frame, pick-up arm assembly,  and rear axle gear (Dia.11).

4.     Bend pick-up arm (black area, Dia. 12 & 13) up, over, and forward to desired position.

5.     Cut a 3/4" by 3/8" rectangle from a .005" thick sheet of shim brass to be used as the pick-up shoe deck. Solder a 3/32" ROUND piece of brass tube across the center, and a bent piece of 1/32" brass rod directly under it on the bottom side as shown (Dia. 14).

6.     Cut two 1" by 1/4" strips of .002" (no thicker than .003") thick shim brass for the shoes. Solder one shoe (A) directly to the shoe deck. Insulate the other half of the shoe deck (wrap in piece of electrical tape) and GLUE on other shoe (B). Bend over both shoes as shown (Dia. 14).

7.     Slid pick-up shoe deck onto pick-up arm, and position about 1" forward front tire/axle centerline. Note where shoe deck ends on arm... remove shoe deck, and solder on a small "dot" of solder at this mark (Dia. 15).

8.     Reinstall the shoe deck and cut pick-up arm flush with front of deck.

9.     Carefully, solder a thin, shielded wire to the insulated shoe, and feed wire up through the pick-up arm (Dia. 15).

10.     Solder on a scrap piece of 1/16" ROUND brass tube to frame, forward of motor, on the SAME SIDE as the TENSION TUBE of the pick-up assembly (Dia. 12 & 13).

11.     For arm tension, rubber band is stretched between, and pinned to the tension tube on the pick-up assembly and the 1/16" tube installed on the frame in step #10 (Dia. 13). Rubber band may be run over or under motor.

12.     Connect the wire from the pick-up arm to one brush barrel on the motor, and with a small piece of wire, ground the other barrel to the chassis. (NOTE: Leave some slack in the wire between the pick-up arm assembly and the motor for movement (Dia. 16).

 
THAT'S IT!!!

    Now, as the newest Builder/Owner/Driver of the worlds only "True" HO scale Monster Truck, it will soon become obvious as to the operation of your truck. You will need some weight and adjustment, but once completed, there will be NOTHING your truck can't do the real ones can.

As for tips on running your truck, I have a million, but none as important as this; "Before you do any shows, exhibitions, or just try to get a friend's eyes to pop out... PRACTICE!!!"

"HAPPY CRUSHING!!!"
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