VIBRATION AND YOUR TIMER

 

More and more fliers are using our timers on large planes and the question keeps coming up about the effects of vibration from the big engines and the ones with a lot of shaking. Unfortunately, we have little data one way or the other on this. We have solicited input from customers who are using our timers in this way, and there is no indication that vibration is any particular problem with a clean and well maintained timer that is used within the capabilities of the timer. We do hear of problems with the DT wire coming off the scroll during the engine run, but it appears that this is caused by overloading the DT release post or by incorrect force of the wire on the scroll. Both are discussed in detail in another "Hints" topic called Early DT Problems.

We have not seen a pattern of timers "shaking apart" due to vibration.

We apply LoctiteŽ to the screws used to attach the faceplate to the clockworks. Our MAX, MAXA, and 3F series have the rear clock posts soldered to the frame, and in some cases, a screw is also used. The brass frame of the clock is fairly thick and all the pinion pins are made of steel. The 3F series has an extra thick faceplate. The cover for the spring drum is crimped into the case. The wires we use for the functions are fairly stiff and made of a special steel imported from Germany. NOTE: The DT wire must never be left loose from the scroll when the engine is running. That can set up some severe vibrations that can fracture the wire.

There is no question that the timer speed will be altered a bit with the engine running than with it off. This effect needs to be offset when setting the timer for the engine run by experimentation. Once set, it should be consistent with that engine and engine speed.

We have a new optional DT scroll that has deeper grooves that looks offers additional protection from the DT wire "jumping" out out the scroll under power. The scroll can be used with any of our timers. You can get ordering information by clicking Here. This is strongly suggested for use with large engines and high vibration engines. It is not generally needed for normal 1/2A through .35 engines.

NEW TIMER DESIGN
The latest batch of MAX III timers incorporates the new deep thread scroll design AND, we have increased the diameter of the DT wire which DOUBLES the stiffness of the wire, making it quite resistant to vibration. This will likely be propagated to our other timer models if we have good success with it.

One customer we know of has used vibration insulation material between the timer faceplate and the fuselage on his big planes with the large engines. In his own words, this is what Larry Davidson of Moneta, VA had to say in an e-mail to another modeler.

"I used a dampening pad that I got from: Small Parts, Inc. (smallparts.com) The pad I bought is .040 X 12" X 12" @ 11.90. I cut out the pad to the outline on the Texas MAX IIIA on my 711 Pilfered Pearl, with a K&B 7.5 Which shakes!, and so far, with about 25 flights, showed no problems. They also sell the pads in different thicknesses and sizes too. "

We welcome your feedback on this topic.


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