Will this motor work?

As you can imagine, we get that question a lot. Here are some rules for evaluating brushless motors for our airframes:


In order to use a motor in one of our aircraft, it will need to be approximately the correct weight, or else it won't be possible to balance the aircraft. This is the most important and basic criteria for selecting a motor. Below are weights for some of the motors we recommend for our aircraft. If you want to know if a certian motor will work in of our airframes, compare its weight to the weight of the recommended motor. Try to choose one within 10% if possible.

Torque 22T-930 57grams
Torque 2830-1095 70g
Torque 2818-900 104g
Torque 2814-820 143g
Torque 2812-720 180g
Torque 4014-T570 280g
Reaper Gr-25 67g
Reaper Gr-35 132g
Reaper Gr-45 193g
Reaper Gr-60 276g


The second criteria is KV, which stands for Thousand RPM per Volt. Look up the motor we recommend and find its KV value. Here is a chart of typical values for our aircraft according to the battery pack used:

3S Lipoly 820-1200KV
4S Lipoly 700-950KV
5S Lipoly 500-650KV
6S Lipoly 350-450KV

Try to choose a motor with a similar KV to the one recommended, or at least within the range above. NOTE: Very inexpensive motors, in addition to having other problems, often have an erroneous KV value advertised for them.

3.Motor and Prop Mounting

Our aircraft use a motor mounting system in which the motor mounts in front of the firewall. This means the motors we recommend come with a part called a backmount or X-mount to attach them to the firewall. Make sure any motor you are considering can mount like this.

We much prefer a bolt-on prop adaptor system, such as the ones used on Reaper, Hacker and Torque motors. The other mounting system, used on most other motors, is called a collet-type prop adaptor. This type of prop adaptor is less secure and less compact. Many 3DHobbyShop aircraft are designed for the bolt-on type adaptor and any motor with a collet-type adaptor will be toolong to fit well. Please call or email us about your application if you want to use a collet-type prop adaptor in a 3DHobbyShop ARF.

4.Take a Chance?

If you have located a motor that is the right weight, correct KV, and has the correct mounting option, you may have found a good motor for your 3DHS aircraft. However, just a word to the wise, motors are literally not all created equal. There are good motors that feature high quality shafts and bearings, pure copper wire coated with good high-temp varnish, good quality glue on the magnet bell assembly, strong bearing mounts...etc. There are many other motors that have only some or none of these features. You can't always tell by looking at them from the outside. This is why we recommend the brands that we do, we know they are built well. If you want to try a less-expensive brand, follow the rules above in your selection and you may strike gold. However, in RC you quite often get exactly what you pay for.

Fly Low


1 comment:

tkna said...

A very informative article as
I'm new to electric RC and this article helped me select a motor for my ZeroGravity Pitts Python after following it's criteria. I was previously going to purchase a weaker motor until I read the above which would, obviously have been a costly mistake. Thanks.