HPI Wheely King Reduction Gearbox (part #87634)

grabcad

This is a Solidworks 2012 model of the HPI reduction gearbox part number 87634. The Solidworks model has a configurable shaft allowing you to use the standard 3mm diameter shaft that comes with the gearbox, or the 5mm diameter output shaft supplied by RC Modelex. I have also included STEP and IGES files for both versions. I've included the textures in the Solidworks files and also included the HPI Racing 540 motor decal/label (this will work with my 540 motor Solidworks model if you download it separately).This gearbox has a reduction ratio of 1:7.4, so it will slow down your motor RPM by a factor of 7.4x. Even though this is an upgrade component for the HPI Wheely King crawler, it makes a great reduction gearbox for a custom RC crawler build, particularly with the 5mm output shaft from RC Modelex.What's really interesting about the way HPI have designed this gearbox is how it attaches directly to the 540 electric motor and uses a standard motor diameter output shaft and provides the same two M3 standard motor fixings on the front of the gearbox. This means that whatever your 540 motor mounts on, this little gearbox can be fitted between that and the motor. It also means that you can daisy-chain two or more of these gearboxes together to provide a tremendous reduction in speed (and increased torque).The one problem for a custom build though is how to attach the 3mm diameter output from the gearbox to a standard 5mm ID drive shaft or coupler. The simplest option would be to use a short length of 3mmIDx5mmOD brass tubing and using a Dremel slice out a slot along the whole length to make a C-shaped cross section wide enough to allow for a grub screw to bite onto the flat of the gearbox shaft. Or, if you have the facility, you could machine a small adapter shaft to take the 3mm diameter up to 5mm. But RC Modelex supply a 5mm OD output shaft to replace the standard shaft in this gearbox, which saves all the messing about making your own adapters.If you're interested in using these parts for a custon RC crawler build, here are the links to the manufacurers websites:HPI Reduction Gearbox:http://www.hpiracing.com/en/part/87634RC Modelex 5mm Shaft:http://www.rcmodelex.com/www-rcmodelex-com/eshop/18-1-transmissions/0/5/618-HD-BLACK-shaft-5mm-for-HPI-GEAR-BOX-87634//download#anch1