Airfield Models - Spinners for Model Airplane Engines

December 20, 2021

Model Aircraft Spinners

I do not consider a spinner to be an optional accessory. The AMA and most clubs require the use of a spinner as a safety measure.

The reason for this is that if an aircraft runs into something, a spinner will cause less damage than a bare crankshaft although I doubt it makes much difference if a 6 lb. model traveling at 90 MPH impacts something.

Fox Slim Jim Aluminum Spinner on O.S. .52 Four Stroke Engine.

Types of Spinners

Spinners come in several varieties and are one or two pieces. There are four methods of mounting them.

One piece spinner that threads on to propeller shaft. These are always metal. (Two spinners bottom left).

Two piece spinner. Backplate is held in place by propeller and propeller nut. Spinner cone snaps into backplate. These are always plastic. (Top left).

Two piece spinner. Backplate held as above. Spinner cone is held onto the backplate using two or more screws that thread into posts in the backplate. I have only seen all plastic examples of this type. (Bottom middle).

Two piece spinner. Backplate held as above. Adapter nut screws onto prop shaft. A bolt passes through the center of the spinner cone into the adapter nut. These spinners usually have a metal backplate and the cone can be either plastic or aluminum. (Top right).

Lastly, scale modelers often make custom spinners for their models because the size and shape they need is not commercially available. These can be mounted in any number of ways.

An assortment of commercial one and two-piece spinners.

Typical spinners

In the upper left is a Carl Goldberg spinner. The cone snaps in place and is removed by wedging a screwdriver between the cone and the backplate.

In the upper right is an aluminum two-piece spinner with hardware.

To the lower left are two one-piece spinners that also act as the propeller nut. In the lower middle is a plastic spinner held together with two screws.

Mounting a Spinner

Before you mount the spinner, you must ensure that the propeller(s) you intend to use with it do not touch the cut-outs in the spinner. Contact with the cut-out can cause catastrophic failure of the propeller and possibly the spinner. Better manufacturers will cut your spinner properly for the propeller for a small fee.

In my mind it is worth it for two reasons: First, it will probably be done right. They have the equipment and the know-how. Second, it makes them liable if you use the product properly and it fails due to a defect in the cut-out.

If you choose to make the cut-outs yourself then try to keep them as symmetrical as possible so that you do not take the spinner out of balance. There are a lot of ways to make the cut-outs but this page does not discuss them. Seek assistance from an experienced modeler before you start hacking away at your spinner.

After the cut-outs are properly made you can mount the spinner and propeller to the engine.

Put the spinner backplate on the engine first.

All two piece spinners have a separate back plate that is held in place by the propeller and prop nut.

Mount the propeller using the propeller washer, nut and spinner adapter nut.

An adapter nut is used in addition to or instead of the prop nut.

The spinner bolt shown threaded into the adapter nut.

The bolt shown here holds the cone in place. The spinner cone goes in place before the bolt though.

The propeller and spinner assembly attached to the engine.

The spinner cone in place. Do not over-tighten the cone retaining bolt. You can crack the spinner or stress it to the point where it could crack in use sending shards of metal flying in all directions.