This article is about how I did the maintenance on my Hobbico Torqmaster 90 deluxe which is a 12 Volt starter for remote controlled (RC) aircraft. I wanted to change the rubber nose to get a better grip on my Avistar Elite spinner. I ended up disassembling the whole unit before understanding what I should have done. This guide documents the steps and tricks I used to reassemble the unit. I hope it may help someone that have the same issue. If not, then I shall use this article as a way for me to remember how I did the maintenance on the starter and which tool I used…

General information

This is a Hobbico Torqmaster 90 Deluxe 12 Volt Starter. It is designed for starting Glow Engines up to .90 cubic inches in size. This starter features an aluminum starter cone with V-Groove for boat starter belts and round rubber insert for airplane spinner cones. The starter has self-adjusting carbon brushes for longer lasting usage and constant contact with the armature. Easy-Press start switch makes starting easy without requiring heavy finger pressure and a built-in finger-guard promises safe starts. Pre-attached alligator clips for easy attachment to a 12 volt battery. The starter is a regular DC brushed motor. Most parts of the starter can be modded or replaced. The switch and the brushes are the one that may need attention.

Required tools

• 8 mm and 10 mm hex sockets
• 2 metal paper clips
• 1 pair of long nose pliers

Maintenance

Replace the rubber insert adapter for aircraft

Hobbico TorqMaster Rubber Insert (Air)

Hobbico TorqMaster Rubber Insert (Air)

The rubber insert can be changed without dissembling the whole unit.  The insert is not glued or screwed into the drive cone but is inserted by pressure. Removing the insert can be done using one of the following ways: If the old rubber insert can be disposed, then the easiest way is to use long nose pliers and try to “pluck” the rubber material around the hex screw until the insert can be removed with your hands. Here is a picture of the insert removed with this method: Another way is to try to unscrew the Drive Cone from the shaft of the unit. Use the 10 mm hex socket and try to push against the rubber to force the socket to get between the nut and the rubber and unscrew. Once you removed the screw from the cone, you will have enough free space for the rubber insert to be pushed to the inside of cone and then you can “pinch” it with long nose pliers and pull it out. The new Hobbico TorqMaster Rubber Insert (Air) can be inserted by pressure into the Driver Cone without difficulty.

Opening the case

The case is held in place by 2 screws. Both screws are 4 inches long (goes through the whole body) and have a 8 mm hexadecimal head. To open the case, remove the 2 screws then pull out the back cover. Warning: removing the back cover will disconnect the brushes from the rotor and you will need to assemble the unit again.

A fixed front cover

For an unknown reason the front cover of the unit seems to be fixed to the rotor. Even if you remove the Driver Cone, you will not be able to detach the front cover from the rotor. This was unexpected but I never found out why I wasn’t able to split the part.

Replacing the motor’s brushes

In the RC world, people usually prefer using brushless motors since they do not have brushes. The main disadvantages of using a brushed motor is that the brushes will wear down and you will eventually need to replace them. In most cases you should not have to change the brushes on a 12 volt RC starter since the motor is not used more than a few seconds each time you go to the field. The brushes should last for a very long time if you take care of the starter by:

• Not using the starter for a too long period of time.
• Not applying too much power (voltage or amperage outside the specifications boundaries).
• Not using the motor in harsh conditions like sand, dust or water.

If the starter gets damage however, you may need to replace the brushes. Here is zoomed picture of the brushes on the Hobbico TorqMaster 90 deluxe: There are multiple sites online where you can buy these brushes but I wont specify any here (google it!). Install the new brushes on the back cover of the unit.

Assembling the unit

Here is a few tricks that may help you assemble the unit. What you need to do is squeeze the front and back cover between the stator (cylinder) and the switch.

The switch

Use masking tape and tape the switch to keep all the moving parts into a single piece. Once the unit is assembled, you can pull on the tape which will slide under the switch and easily be removed without leaving a greasy or sticky finish.

The brushes

Installing the brushes back on the rotor is probably the hardest part to do. The problem is that the spring of the brush must be compressed almost completely to be able to insert the rotor between the two brushes. I am also suspecting that you may need a special tool for doing it. However, I found out a nice and easy trick for keeping the springs compressed while having your hands free for putting the rotor back in place: use paperclips. The goal is to use small and easily bendable paper clips to “hold” the compressed brushes leaving enough free space for the rotor. Then, you bend each clips so they go through the bolt hole of the back cover. The following image shows the paper clips in place: Align the rotor on the back cover bearing and slide it in place. Do not forget to add the switch before assembling the unit. Once completed, use long nose pliers to pull out the clips from the hole which will release the brushes:

The driver cone

Hobbico TorqMaster 90 Old / Used Drive Cone

Hobbico TorqMaster 90 Drive Cone

The Driver Cone does not require any explanation. Simply push the cone on the motor’s shaft while aligning the pin on the shaft until it is fully inserted into the cone. Then screw the cone in place using the 10 mm hex socket. Here is a picture of the shaft without the Driver Cone inserted:

Note: If you actually changed the rubber insert, it is much wiser to screw the Driver Cone in place before installing a new rubber insert.