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Elevator rail for drive belt

von Peter Ziegler
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Rubber-powered models are a fascinating aspect of our hobby. It doesn’t matter whether they belong to one of the FAI classes (F1B, F1D, Coupe d’Hiver) or another class (Peanut, Walnut, Kit-Scale, Jumbo-Scale, P30, etc.).

What they all have in common is a propulsion system using rubber bands, which must be wound once they’re secured in the model. There are various methods for doing this, as shown in Figures 1 through 5.

With all of these methods, there’s always the risk of damage or even destruction of the model if a rubber cord snaps. This is true even with proper preparation of the rubber cords—stretching, lubricating, and adjusting the number of turns. Rubber cords are, after all, consumables.

I’ve been thinking about how I can avoid this risk by winding the drive train outside the model and then inserting and securing it inside the model once it’s fully wound.

The solution I’ve been using for years: a tensioning rail made from an aluminum U-channel. Corresponding to the usable

fuselage length, the aluminum profile (available in various sizes at hardware stores) is cut to length with a bit of extra length and notched at both ends. These notches are later widened to accommodate the spool and locking pin. The extra length is necessary because a stop is glued to the rail.

The unpanned fuselage, ready for the airframe, is prepared. The intended anchor made from a round bar is replaced with a brass or aluminum tube. A piece is cut from this and machined to match the clear width of the U-channel (Figure 6).

The remaining piece is split into two parts. The three parts are threaded onto a kebab skewer and inserted into the holes in the fuselage reinforcements. Now the aluminum rail is inserted and secured in a vise. The fuselage now hangs from the rail, and the stop at the fuselage nose can be glued to the rail. ■

More pictures on the next spread →


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1 By hand.
2 With an assistant and a winch.
3 With the model secured in the lifting block and a winch.
4 As in Figure 3, but with a protective tube over the rubber.
5 Secured by the feet and pulled taut with a winch.
6 The side pieces, cut to length and machined as needed, are glued into the holes in the reinforcements (Figure 8).
7 Before securing the rubber, a guide for the aluminum rail is made from scrap wood. Preferably attached to a rib (Figure 9).
8 The previously prepared drive line is fitted with the spool and the hook at its ends, and both parts are secured with dental rubber bands. Clamp the rail in the vise, hook the spool in, and tension the line (Figure 10).
9 The hook has two holes. The locking pin is inserted into one of them to prevent the rubber band from unwinding; the propeller is attached to the other (Figure 11).
10 The unit prepared in this way is inserted into the fuselage as far as it will go. The guide ensures that the spool is in the correct position (Figure 12).
11 The drive train is now secured in the model with a locking pin (Figure 13).
12 Hook the propeller in place, remove the locking pin, and pull the guide rail out of the fuselage (Figure 14).
13 The fuselage nose with the propeller is pulled into the correct position by the tension of the rubber band, and the model is ready to take to the skies (Figures 15 and 16).
14 I use this method for most of my models that have a suitable fuselage cross-section, regardless of how large or small they are—whether they’re utility models or scale models. Damaged or destroyed fuselages have been a thing of the past ever since. Figure 17 shows all the components again.


3/2025
Article from the issue 3/2025


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