One of the features that Chiappa touts about the Rhino are the roller bearings used in the action. The Rhino has four such bearings, two each on the hammer spring lever and the return lever:
The picture shows the back (underside) of the two parts, because the rollers are not visible when installed in the gun. (Please refer to pictures from previous episodes showing these parts installed in the Rhino.)
Each lever has a captured roller bearing on which an arm of the mainspring rides. The other roller on each is on an open pin, and the rollers are easily removed. (They’re also easy to lose when installing the parts in the gun, unless they’ve been greased ahead of time and thus stuck to their pins as they’re assembled.)
The mainspring rollers ride along the surface of the wire torsion mainspring. As the parts move they slide up and down the mainspring; if the rollers weren’t there this sliding would a source of significant friction. This approach isn’t completely successful, however, due largely to how the rollers are constructed.
Because the surface of the rollers is flat the mainspring can ride from side to side. At virtually no time does the mainspring not rub on the sides that contain the rollers, and this means friction. If the roller bearings are designed to reduce friction, they are only partially successful.
There is another potential downside to this design. Though I had no problems in testing, there exists the possibility – however remote – that the mainspring could “jump the tracks” and come off the roller. If that happened the gun would be non functional until disassembled. This is not dissimilar to a rare condition faced by the trigger return spring in the small frame Dan Wesson revolvers, which on occasion would slip off its saddle on the trigger, tying up the gun. Again, I haven’t seen or heard of any problem, but having experience with a revolver which on occasion does exhibit such a weakness I’d prefer that Chiappa err on the side of prevention.
The solution found for the Dan Wesson may be useful in the Rhino: make the part with a groove in which the mainspring can ride. This would ensure that the mainspring is always following the most friction-free path, and would make it much less likely that the mainspring could be forced off track.
The other two rollers transmit the mainspring power to other operating parts. The hammer spring lever’s roller rides in a slot on the hammer (clearly visible in earlier pictures.) The roller bearing is always pushing on the side of that slot to power the hammer, and sliding back and forth as the hammer moves. Were it not for the roller bearing, this sliding – under the full force of the mainspring – would make the gun much more difficult than it already is to cock in either single or double action.
The other roller, on the return lever, pulls the lifting lever (hand) back to the rest position as the trigger is released. This force is transmitted back through the action, working against the leverage of the parts, to reset the entire lockwork. Excess friction at this point could cause the trigger to stick during reset, and that’s what the roller is designed to prevent.
Given their importance to the design, I was surprised to find that the machining quality wasn’t as good as the rest of the gun. The operating surfaces of the bearings were surprisingly rough and no doubt generated more friction than they probably should. In addition the bearings were quite sloppy on their pivots, which raises the possibility of backlash and attendant friction losses. This sloppiness also contributes to the mainspring friction problem detailed above, as the rollers get pushed to one side and create a trough in which the mainspring rides.
Closely fitted bearings with perfectly smooth surfaces should result in small but noticeable changes to the operating effort that the Rhino requires, as well as helping to smooth the very gritty trigger return the gun exhibits. Though I haven’t analyzed this from a strength of materials standpoint, replacement bearings carefully made from impregnated bronze might be an excellent choice to improve the Rhino’s function.
I hope this teardown of the Chiappa Arms Rhino revolver has been useful to you!
-=[ Grant ]=-