APPLICATION: WORKS WITH SAVAGE 21 RTR, 25 RTR, & 25 SS
The HPI Savage is a big & heavy truck and it has a reputation for breaking/bending/twisting the stock dog bone shafts. This can happen with the stock 21BB engine, and it can be a real problem when upgrading to an even more powerful engine! This Hot Bodies upgrade driveshaft connects the center to the front differential. These replace the cheaper HPI Savage dog bone design center drive shafts with an upgraded design that includes a universal style joint on one end for smooth action.
WHY BOTHER TO UPGRADE TO A UNIVERSAL STYLE SHAFT?? Why not just use the stock dog bones or some replacement heavy duty dog bones? Well, this can definitely be done. In the case of the stock Savage dog bones, they have proven to not be very reliable and tend to twist, bend, break. Heavy duty dog bones could also be an option. Regardless, there are some definite advantages to using a universal style drive shaft instead of a dog bone.
Read what was written in RC Nitro magazine (April 2003, pg. 95) regarding Universal Joint axles:
"A dogbone is the most common type of drive axle; it looks a bit like a dog bone and uses pins to engages slots in the outdrives. It works, but the parts tend to chatter when the steering hubs turn, and the parts operated with a fair amount of friction. Universal-joint axles operate more freely and wont chatter; that means better performance and extended wear."
The above comments are written more specifically about the outdrive shafts going out to the wheels, but the principle of less friction in a universal joint still applies with the center shafts.
LESS FRICTION=MORE AVAILABLE POWER TO THE WHEELS!
VERY IMPORTANT NOTE: We recommend that customers check to be sure the factory set screw on the universal joint is tight before installing these shafts on their truck. We also recommend that these set screws are periodically checked to make sure that they do not vibrate loose over time. These factory set screws have a special coating of thread locker on them already. The type of thread locker that is on them appears to be the type that comes already pre-applied and cured before the set screw is ever used. One of the reasons that this is done is probably to prevent someone at the factory from getting too generous with conventional liquid thread locker and gumming up the whole joint with the stuff! The nice thing about the factory set screws with this patch of pre-cured thread locker on them is that you should be able to periodically check (and re-tighten if necessary) the set screw and not worry about ruining the thread lock effect. With conventional liquid thread lockers, if you move a screw after the loc-tite has cured, you can actually break the thread lock bond. On the 6 shafts we tested, we found some of the factory set screws on our shafts to be a little less tight than we would prefer so we tightened them up. That is why we recommend customers check to make sure these set screws are snug right from the start and to periodically re-check them. This is just a fact of life when operating a nitro RC vehicle that generates such powerful vibrations. All metal-metal fasteners are at risk of vibrating loose - such is the nature of this hobby! When checking the set screws, be sure to use moderation and dont strip out the threads! Please do not ask us (or Hot Bodies) to replace your driveshaft because you had a "gorilla hand" and stripped the set screw threads! We are just offering these recommendations to our customers as a suggestion to help them out.
ANOTHER TIP: Some people have also taken larger diameter heat shrink tubing (can be found in the electrical department at places like Home Depot) and cut off a section and put a narrow section on the cv joint so that if the set screw vibrated loose, then the pin would not able to fall out. Just make sure the heat shrink tubing you buy is large enough to fit over the cv joint and then be sure the shrink it properly with a heat gun or carefully with a flame.
