USING THE DT FUNCTION ON DT, MAX, 3F, & ULTIMATE
The scroll function for DT works basically the same on all the Texas Timers. The DT can be used in a number of way. For example, a quick DT for critical first test flights, a short DT for small fields or trim flights, or a full DT time for competitive flying. The following will provide some additional guidance on how to set up the DT. If these guidelines are not clear, do not hesitate to contact us with any questions.
ALWAYS START WITH THE SPRING FULLY WOUND.
You do not need to use excessive force, just wind like you would
you would a spring driven wristwatch or clock, until it is snug.
SETTING UP THE ENGINE KILL FUNCTION
· The engine will kill when the kill wire releases on the timer. The time markings on the faceplate are for reference only. You will need to run tests to get the exact engine run time you want. Most fliers make pencil marks on the faceplate for the run times they want, and launch when the red mark on the dial hits that point. Do this with the engine running, as vibration will have some effect on the clock speed.
MOVING THE DT WIRE
· The easiest way to move the DT wire is to press down on it from the top and position it in the thread groove you want. If the wire has gotten trapped under the bottom turn of the scroll, you may need to use a screwdriver to pop it out.
SETTING UP THE DT FUNCTION
· The DT time is fully adjustable from before your engine quits (typically not a good thing), to the maximum run time specified on your particular timer (three or five minutes).
· The DT time is controlled by a combination of the number of scroll turns down from the top that you place the DT release wire, and the relative position of the release point on the scroll when you launch.
· The position of the engine release disk and the scroll are independently adjustable by loosening the brass screw in the scroll. If you remember nothing else, remember this, THE BRASS SCREW IN THE SCROLL IS LEFT- HAND THREADED. To loosen it, you turn the screw CLOCKWISE TO THE RIGHT. Always hold the scroll or disk when loosening the screw to prevent excessive force from being transferred to the gear train. A busted gear can result if too much force is put on it.
· If you want to DT as soon as the engine the engine quits, then set the DT wire release point on the top of the scroll to be somewhat greater than when the engine kill wire is released. The timer runs clockwise when in the "run mode". This needs to be tested on the ground to avoid the effects of DT with the engine running. The engine does not need to be running for this test, as you are only setting the delay between the engine kill and DT. The brass screw does not need to be over-tightened. Just snug it up. Normal winding of the clock will tend to keep the screw tight. It is not good to break off the screw by turning it in the wrong direction or over tightening it.
If you want to DT a short time after the engine quits, then simply
scroll release point relative to the slot on the engine kill, and snug up the
WHAT ABOUT DT IN 15 SECONDS, FOR A TEST FLIGHT WITHOUT A
· This is a piece of cake. Just set your scroll position relative the engine kill release, so you get 15 seconds. Testing on the ground is adequate. Use the appropriate groove in the scroll. Always test before you launch.
WHAT ABOUT ANY DT TIME?
· Again, not problem. You just need to set the scroll position relative to the engine kill slot (or launch mark) to any time you want.
The scroll turn rate varies with the timer model, so you need to
do a bit of experimentation. In general the scroll will turn 360 degrees
in the 23 to 40 second range. Assuming you have
set it to DT at about the same time as the engine kill, then each groove down in
the scroll will add so much to your DT time. You need to test this and adjust
it accordingly. This is not a calibrated dial setting. Every timer will
be a bit different. You need to test it.
SETTING UP THE TIMER FOR A TWO MINUTE MAX FLIGHT.
· This is pretty well described in the procedure for any setting you want. For all practical purposes you can ignore the engine run time, and set this on the ground.
· Trip your stopwatch timer at the faceplate mark you would launch at for your desired engine run. When your stopwatch reaches 2 minutes, stop the timer with the start wire. Hold the engine kill disk fixed, loosen the L-H thread brass screw in the scroll, and rotate the scroll to the point where the DT wire will be at the exact point of release. Then, you will DT every time, at 2 minutes after launch. We would personally rotate the scroll a few degrees to add a few seconds to this time.
Obviously, you need to count scroll grooves or threads from the
top to get this setting.
A FEW THINGS TO REMEMBER
· DT time is set by the number of thread turns below the top of the scroll you place the wire, and by the position of the scroll release point at the top of the scroll.
· The scroll holding screw has reverse or backward left- hand threads. To loosen the screw, you turn the head to the right (clockwise).
It is not good to DT when the engine is running, so be sure and
test on the ground before you launch, particularly if you are trying to DT right
after engine kill.
CONSTRUCTION OF YOUR DT SYSTEM
· The purpose of this is not to tell you how to DT, but to outline how to connect the DT line to this timer.
· The DT release line needs to apply enough force on the DT release line of the timer to enable the wire to release.
But, the line tension should not be so great that if creates
excessive drag on the scroll wire. The DT line release is intended to be at the
bottom of the post.
· You must use a washer or something similar to place the DT line above the DT wire hinge point. It is not acceptable to use a wire or rubber band directly on the timer DT post. You must use a hard surface like a small fishing washer or link to connect to the DT release post. Failure to do this may result in insufficient torque to release the DT line. Never allow the DT line to the stabilizer to rest at the bottom of the DT post on the timer. This is why a washer or spacer is required. Note that we now carry the correct split rings to use on these posts.
· Do not use excessive force on the DT line. Test your timer to be sure the line tension will not force the wire out of the threads, or that it causes the timer to quit. This is not a delicate setting. Just keep the line tension reasonable, and be sure you have the split ring connected to the timer post at the very bottom. You need the split ring or something on the line, so it can not slip down to the post hinge point. There is no torque there to pull the wire off the scroll.
· A bit of on-the-ground testing should let you easily and quickly set the wire force on the scroll. In most cases, no adjustment to the factory setting should be needed.
· A quick test of the scroll force is to let the DT wire rest on the top of the scroll. The tip of the wire should be 1/32" or less inside the inner core of the scroll.
· The DT wire should be at about the 6:30 position when placed on the scroll threads at your point of plane release. 7:00 or later could cause excessive drag on the scroll. Less than 6:00 can result in inadequate "holding force" when at the top of the scroll.
should be delivered to you set up properly, but no serious flier ever launches
without testing all the systems on the ground, and with the engine running.