The biggest R/C buggy in existence?
This is the large scale radio controlled buggy that I built several years ago. It's 61 inches long and 32 inches wide. It weighs 120 pounds. The drive portion is built more like a go-kart than a R/C car. I try to run it at least a few times a year, and I have been continually making improvements and upgrades as needed.
The engine is a 120cc two stroke from a Lawn-Boy push mower. It's mounted so that the crankshaft is horizontal, and the output shaft has been modified to accept the centrifugal clutch where the mower blade was. The transmission is a Comet TAV 30 continuously variable belt drive transmission that automatically varies from 2.68:1 ratio to .90:1. This allows the car to have excellent power for tire spinning acceleration from a standing start, and still be able to reach high speeds without shifting gears. The chain ratio is 4:1. The original Walbro carburetor was replaced with a Tillotson HL series diaphragm carburetor that provides much better performance and adjustability. The stock muffler was replaced with a RLV G2 tuned pipe from a Yamaha racing kart.
Comet TAV-30 below.
Final drive chain.
The frame is made from lightweight 3/4" steel tubing. The engine and CVT are mounted on a separate cradle that bolts to the frame with rubber mounts and is easily removable for servicing.
The front suspension is independent unequal length tubular control arms using spherical rod ends at all pivot points, and is fully adjustable for caster, camber, and toe. The upper control arms are made from 1/2" x .049" wall seamless steel tubing and 1/4" rod ends and the lowers are 5/8" x .049" tubing with 5/16" rod ends.
The rear suspension is a swing-arm type constructed of 5/8" tubing and 3/8" rod ends. The rear differential and axles are from a small riding lawnmower. A seven inch stainless steel vented disc brake is mounted on the drive sproket.
There are no commercially available hobby servos that are powerful and rugged enough to steer a car this big. I tried a pair of the biggest giant scale servos I could find, and they couldn't even begin to steer the wheels. I came to the conclusion that I would need to build my own servos. The steering and the brake are both actuated by 12 volt gear motors. I've created a separate page on building high power servos.
The throttle uses a standard hobby servo mounted on the carburetor.
There is a 12 volt, 9 AH sealed lead/acid battery to power the steering and brake motors, and a 5 volt regulator to power the receiver and control circuits using the same battery. All of this is remotely controlled by a standard Futaba 3 channel FM radio control system.
The front end rides on 12.5x2.25 tires on 8 inch rims, and the rear is on 15x6.00 Goodyear Terra Tires on 6 inch rims. Alternating tread blocks were removed from the rear tires to provide ultimate traction.
If you have built a large scale R/C car of your own please let me know, I'd love to hear about it.
bron: www.fieroaddiction.comThis is the large scale radio controlled buggy that I built several years ago. It's 61 inches long and 32 inches wide. It weighs 120 pounds. The drive portion is built more like a go-kart than a R/C car. I try to run it at least a few times a year, and I have been continually making improvements and upgrades as needed.
The engine is a 120cc two stroke from a Lawn-Boy push mower. It's mounted so that the crankshaft is horizontal, and the output shaft has been modified to accept the centrifugal clutch where the mower blade was. The transmission is a Comet TAV 30 continuously variable belt drive transmission that automatically varies from 2.68:1 ratio to .90:1. This allows the car to have excellent power for tire spinning acceleration from a standing start, and still be able to reach high speeds without shifting gears. The chain ratio is 4:1. The original Walbro carburetor was replaced with a Tillotson HL series diaphragm carburetor that provides much better performance and adjustability. The stock muffler was replaced with a RLV G2 tuned pipe from a Yamaha racing kart.
Comet TAV-30 below.
Final drive chain.
The frame is made from lightweight 3/4" steel tubing. The engine and CVT are mounted on a separate cradle that bolts to the frame with rubber mounts and is easily removable for servicing.
The front suspension is independent unequal length tubular control arms using spherical rod ends at all pivot points, and is fully adjustable for caster, camber, and toe. The upper control arms are made from 1/2" x .049" wall seamless steel tubing and 1/4" rod ends and the lowers are 5/8" x .049" tubing with 5/16" rod ends.
The rear suspension is a swing-arm type constructed of 5/8" tubing and 3/8" rod ends. The rear differential and axles are from a small riding lawnmower. A seven inch stainless steel vented disc brake is mounted on the drive sproket.
There are no commercially available hobby servos that are powerful and rugged enough to steer a car this big. I tried a pair of the biggest giant scale servos I could find, and they couldn't even begin to steer the wheels. I came to the conclusion that I would need to build my own servos. The steering and the brake are both actuated by 12 volt gear motors. I've created a separate page on building high power servos.
The throttle uses a standard hobby servo mounted on the carburetor.
There is a 12 volt, 9 AH sealed lead/acid battery to power the steering and brake motors, and a 5 volt regulator to power the receiver and control circuits using the same battery. All of this is remotely controlled by a standard Futaba 3 channel FM radio control system.
The front end rides on 12.5x2.25 tires on 8 inch rims, and the rear is on 15x6.00 Goodyear Terra Tires on 6 inch rims. Alternating tread blocks were removed from the rear tires to provide ultimate traction.
If you have built a large scale R/C car of your own please let me know, I'd love to hear about it.
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