On 20/12/2017 21:43, Edmund Liem edmundliem_at_gmail.com
[Indoor_Construction] wrote:
> Now I wonder what is the best knot for the tiny 0.4g rubber? And when
> do you do the knot in regards to the lubrication?
I use two kinds of knots for all my rubber, from F1D indoor to F1B. Both
were tought to me by Bror Eimar. Both need to be tied to lubed rubber
strip, but the lube should be of low viscosity for F1B motor break-in,
otherwise the knots may slip and the strip cut through itself. For
indoor, I do not break-in individual motors, but if I do some break-in,
stretch a larger amount of rubber before cutting to width, so here knot
tied to strip lubed with thicker silicone will hold the loads of winding.
The first is called "norsk strikknut". It starts with a square knot,
then extra knots are tied to each end, and all three knots are carefully
pulled together. See attached picture. This knot has the advantage, that
the "ends" of the rubber strip leave the knot in opposite directions, so
I feel that it stands better the wear and loads of strip stretching. For
indoor use, on the other hand, it is harder to control the position of
the knot, so making motors to precise weight is harder. Yet I still use
this knot for the motors that I expect to see hardest strain.
Another and easier knot that I use is made by putting the ends of the
motor over each other (pointing the same way), then tying a square knot
with the ends. Next the free ends are turned one turn around the "stem"
of the knot (in the same "direction" as the square knot goes), after
which the ends are out through the loop of the square knot, and the knot
is tightened. In practice, I make the square knot, put the tip of the
forefinger through the loop and twist my wrist to turn the loop one
round while holding the base of the knot with other hand, and push the
free ends through the loop. This loop has both strips exiting the same
direction, so when the strip is pulled they kind of stretch against the
body of the knot, which is not good. But it is easy to make so if I need
to tie a broken strand on F1B practice motor I use that. Also it is easy
to control the length of the free ends, so when making indoor motors I
have better control of the motor weight. Talking of which, I usually
make my motors by cutting them to a controlled amount of extra weight,
then have a short strip or two as a reference of that extra weight. Thus
I know how long free ends I aim to leave to the motor when tying the
knot, and once the knot is tight I trim that much of the ends (hopefully
next to the knot) and end up with a motor exactly to the weight limit,
and minimal ends protruding out of the knot. This latter knot is quite
easy and light, so especially for F1M, if I end up with an overweight
motor, I tie another similar knot next to the first one, use the first
knot to pull the second tight, and finally cut off the first knot.
Typically I'f end with a motor that is not too much underweight.
On 21/12/2017 3:12, Don Slusarczyk don_at_slusarczyk.com
[Indoor_Construction] wrote:
> thin the rubber can "stick" to itself and not unwind completely or
> tends to bunch rubber in the back and cause stalling. The bunching would
> be on models like Bostonian or similar with high RPM and long motors or
> on something with thin rubber like ministick. This was with Dow 33
> grease.
Dow 33 is extremely thick grease. F1B guys used to "thin" it with thin
silicone fluid to get proper grease for their motors. The 10,000 to
15,000 cTs fluid is much thinner, something like (sugar syrup). In my
experience it does not make the rubber stick to itself.
-Tapio-
- application/x-ygp-stripped attachment: stored
Received on Thu Dec 21 2017 - 06:23:51 CET