TRF Tips and Techniques Comments Thread.

[prfesser]

Re: Chuck's suggestion of a wire-wrap tool for making starter blanks. Tim suggested that yesterday when we were making them, but unfortunately the hole in his particular wire-wrap tool wasn't large enough for both ends of the copper lead wires. Otherwise it surely would have saved some time.

 

[cwbullet]

Re: Chuck's suggestion of a wire-wrap tool for making starter blanks. Tim suggested that yesterday when we were making them, but unfortunately the hole in his particular wire-wrap tool wasn't large enough for both ends of the copper lead wires. Otherwise it surely would have saved some time.

What is the AWG of your wire? Both ends at the same time?

 

[prfesser]

It was 24ga. I could get one end in, but not both, so I couldn't wind the "lower" end of the starter. So it goes. In any event we were making only a few dozen, and I've gotten pretty good at winding them by hand over the last 25+ years.

 

[cwbullet]

It was 24ga. I could get one end in, but not both, so I couldn't wind the "lower" end of the starter. So it goes. In any event we were making only a few dozen, and I've gotten pretty good at winding them by hand over the last 25+ years.

I might do a how-to. I have never had any issue with a 24 awg wire.

 

[jqavins]

Get a Good Set of Nippers

Contibutor: @cwbullet

For my rocket toolbox and beside every 3D printer I own, I keep a set of Hakko or IGAN cross-cutters. These little tools are invaluable for cutting almost anything you need on the field (except kevlar). If you use them well, you can even use them to trip a wire.

I prefer IGAN 170 and 330s. You can find a cheaper set, but these will last a long time. I have used mine so much that I have worn the label off of them.

That's a good tool to have on hand, but I believe a nipper is this:


Which, come to think of it, would probably also be good to have the range box and maybe also sitting beside a 3D printer.

 

[cwbullet]

That's a good tool to have on hand, but I believe a nipper is this:
View attachment 568152

Which, come to think of it, would probably also be good to have the range box and maybe also sitting beside a 3D printer.

I have seen them both called that.

 

[jqavins]

Tape for Motor Retention

Contributor: @cwbullet

One of the most valuable and easy methods to retain a motor is tape. It can be used in minimum diameter or with a motor mount and both high and low power.

But not for a cert flight, at least not under NAR rules; I don't know about Tripoli.

Minimum Diameter Wire Motor Retention

Contributor: @cwbullet

I found this tip in an old version of Apogee's Monthly New Letter. I have only used it for low power, but it would probably work up to mid-power.

I like to use this even where there's a motor mount. Just poke the wire through the aft centering ring, and I fold the ends down to rest against the ring. It's much less unsightly than a regular engine hook.

 

[cwbullet]

But not for a cert flight, at least not under NAR rules; I don't know about Tripoli.

I like to use this even where there's a motor mount. Just poke the wire through the aft centering ring, and I fold the ends down to rest against the ring. It's much less unsightly than a regular engine hook.

Thanks. Good tip.

If any one has a tip, please post it here and I will move it to the thread. If you put it in the format I am using, I will just move it. It can be to a link to post in another thread.

 

[augendoc]

Measure epoxy on a postal scale. Most epoxy I use is a 50/50 mix. This also helps keep the 2 bottles level/equally used. I mix more than I need to make sure I do not run out, and to help rotate supplies. This 15-minute epoxy is over a year old. The mighty toothpick is one of my favorite mixer and applicator tool!

A couple of tips for measuring epoxy by weight:

1. Use a scale appropriate for the amount of epoxy you are measuring. If you want to measure only a few milliliters, consider a scale measuring in 1/100ths of a gram. That scale really usually only measures to 0.1 gms with ±0.05gm as the 1/100th unit. If you use a larger scale you can sometimes add a couple grams before the scale will even register.

2. Epoxy mixing instructions are almost always quoted by volume. If you measure Bob Smith Industries epoxies by weight, the SDS for all their epoxies lists a specific gravity of 0.97 for hardener and 1.15 for resin. That works out to a Hardener: Resin ratio of 1:1.185 by weight, or a Resin:Hardener ratio of 0.843:1.

The BSI FAQ says the weight ratio of all their epoxies is H:R 1:1.1 but the SDS sheets say different. BSI's opinion in the FAQ is that the hardener and resin need to be within 10% of each other and the 1:1.1 ratio complies (meaning they think you can measure 1:1 by weight and you'll be fine).

If you do it that way you will end up with leftover resin. Being a stingy, compulsive person not wanting to waste material I weigh it out at a 1:1.19 ratio and have not had any problems.

These ratios are for BSI epoxies only. I cannot speak for other brands.

 

[cwbullet]

Does anyone have a good tip or link for filling spirals?

 

[Tech 68]

Being lazy and trying to find an approximate Coefficient of Drag for my "short kit" Sidewinder, I stumbled across this resource on the web. Unlike the ones only offering a synopsis and wanting payment for the full "paper", this one looks to be free. Digging into it casually, it appears to have information on *everything*.

https://www.researchgate.net/publication/351783801_AERODYNAMIC_ANALYSIS_ON_MISSILE_DESIGN

 

[neil_w]

I've given this tip many times on this forum but here I am submitting it for posterity.

When using Estes BP motors, fold the igniter wire over the paper and then attach the igniter clips to the paper + wire. This will give the clips something solid to hold onto, and will keep the connection secure until launch. An extra curl of the wire on the paper (optional) will give more contact area for the clip.

 

[John Kemker]

For the nose weight post, #28, "chocolate moles" made me think of some sort of strange Easter candy...

 

[Grog6]

FWIW, a wire wrap tool is designed to wrap a 1"piece of 30awg wire over a .025"square pin.
I repared a PDP-8 backplane in hs. 30 awg wire wrapped over a 20 awg wire is close to the right sizes. Also, the silver-plated ww wire solders easily.

 

[jqavins]

Does anyone have a good tip or link for filling spirals?

Keep calm and carry on.

 

[cwbullet]

Keep calm and carry on.

Great tip, but I might need more.

 

[T-Rex]

But not for a cert flight, at least not under NAR rules; I don't know about Tripoli.

Um, not true:

"Is (are) the rocket motor(s) firmly restrained in the model? Check for engine mount integrity to prevent a "fly through" (Is a thrust ring used?). Check for a motor hook or similar motor restraint. Carefully check taped or friction fit motors for tightness. Ask the modeler what adhesives were used during assembly. Are clusters wired in parallel?"

From the checklist on the back of the NAR L1 & L2 certification application. L3 doesn't specify. (Bold added for clarity)

 

[jqavins]

Hmm, odd. Our club's certifiers have sent a couple of flyers off to add positive retention of some sort because, supposedly, tape and friction are not sufficient. I guess they've been doing it wrong.

 

[cwbullet]

Hmm, odd. Our club's certifiers have sent a couple of flyers off to add positive retention of some sort because, supposedly, tape and friction are not sufficient. I guess they've been doing it wrong.

I am not sure. I would never fail someone for using tape. I would check to see the motor is secure.

 

[cwbullet]

FWIW, a wire wrap tool is designed to wrap a 1"piece of 30awg wire over a .025"square pin.
I repared a PDP-8 backplane in hs. 30 awg wire wrapped over a 20 awg wire is close to the right sizes. Also, the silver-plated ww wire solders easily.

That is here I experienced it. I am shocked at how well it works on round wires too,

 

[OverTheTop]

That is here I experienced it. I am shocked at how well it works on round wires too,

The original use of square posts had seven wraps of the wire-wrap wire around them. That made 28 contact points, and the pressure applied by the wrap tool created 28 cold-welded contact points due to the pressure at the interface. It is a very reliable connection system.

Using round wire for the middle means you don't get the cold welding of the joints, so they may be suitable for use, or possibly not. A little more luck is involved.

 

[cwbullet]

The original use of square posts had seven wraps of the wire-wrap wire around them. That made 28 contact points, and the pressure applied by the wrap tool created 28 cold-welded contact points due to the pressure at the interface. It is a very reliable connection system.

Using round wire for the middle means you don't get the cold welding of the joints, so they may be suitable for use, or possibly not. A little more luck is involved.

Luck is not what I have experienced. I just ran the data - over 10K igniters and 6 failures. That is less than 0.07%. I will live with that luck.

 

[John Kemker]

Luck is not what I have experienced. I just ran the data - over 10K igniters and 6 failures. That is less than 0.07%. I will live with that luck.

I've used a wire-wrap tool to wrap nichrome around wires and never experienced a problem, either.

While I understand @OverTheTop 's points about the cold welds when using square posts, those are intended for long-term reliability. In our use case, we just need it to last long enough to be destroyed by the motor's ignition.

 

[jqavins]

I've used a wire-wrap tool to wrap nichrome around wires and never experienced a problem, either.

While I understand @OverTheTop 's points about the cold welds when using square posts, those are intended for long-term reliability. In our use case, we just need it to last long enough to be destroyed by the motor's ignition.

I was taught that the purpose of the square posts is that the corners bite through the very thin insulation on the wire. I recall pulling a few apart that didn't seem to be any kind of welded.

 

[John Kemker]

I was taught that the purpose of the square posts is that the corners bite through the very thin insulation on the wire. I recall pulling a few apart that didn't seem to be any kind of welded.

I've not seen wire-wrapped boards insulated at the post. As a matter of fact, every wire-wrap tool I've ever used had an wire-stripper built in to the handle. You strip then wrap.

 

[OverTheTop]

I was taught that the purpose of the square posts is that the corners bite through the very thin insulation on the wire. I recall pulling a few apart that didn't seem to be any kind of welded.

The wire should be stripped before it is wrapped around the pin. There is a later "modified" wrap where two turns of insulated wire were added for strain relief where it exits the pin, but the insulation was not pierced there. The actual cold-weld points will be quite tiny (hence enough pressure to cold weld) and when you unravel the joint those welds will easily break, but they are there .

Standard strip length for both standard and modified wraps was 1", with the tool design providing the extra two wraps on the modified versions.

 

[cwbullet]

I've used a wire-wrap tool to wrap nichrome around wires and never experienced a problem, either.

While I understand @OverTheTop 's points about the cold welds when using square posts, those are intended for long-term reliability. In our use case, we just need it to last long enough to be destroyed by the motor's ignition.

That makes sense. I misinterpreted it.

 

[cwbullet]

I've given this tip many times on this forum but here I am submitting it for posterity.

When using Estes BP motors, fold the igniter wire over the paper and then attach the igniter clips to the paper + wire. This will give the clips something solid to hold onto, and will keep the connection secure until launch. An extra curl of the wire on the paper (optional) will give more contact area for the clip.
View attachment 569430

Added for today - thanks.

 

[cwbullet]

Any one have a tip for today?

 

[Huxter]

Use Glad 'Press n Seal' wrap to cover rockets parts that you do not want to paint. The wrap is immutable to paint. It's thicker and handles better then the thin stuff. It has a slight sticky to it, so make sure the sticky side is out - it will leave residuals on the rockets. If you haven't tried the stuff, I suggest you do! Oh yeah - it's great in kitchen too!