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  #31  
Old 11-14-2008, 10:42 AM
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Doug Sams Doug Sams is offline
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Originally Posted by Jeff Walther
I am unclear on what you mean by current share.
Some electronic components have resistances with positive temperature coefficients - the resistance goes up with temp. Thus, as you postulated, the lower impedance part will get the most current and heat up faster resulting in more even distribution of the current - ie, current sharing. OTOH, other parts have their resistances go down with temp and thus, if they start out hogging an unfair share, it only gets worse over time.

All that said, I prefer not to count on any particular change in resistance of the ignitor, and instead try to pick them to be within ±0.1Ω of each other at the start.


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What is no-nicks? :-)
These are specially designed wire strippers just for wire-wrap wire that minimize the chances of nicking the wire.


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Do you have a method of soldering in the field or do you do all your prep at home?
In my experience, there's just way too much going on at the field for me to be able to do such tedious stuff. Maybe somebody like the late Gordon Cooper could keep his cool during highly stressful moments, but for me, fighting the wind, heat and dripping sweat while watching the flight line and entertaining three impromptu passers-by, I struggle greatly to do any sort of complex prep at the range. I much prefer do it at home ahead of time.


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What happens if you attempt to wire wrap an Estes igniter lead around a square post? I'm thinking about the header strips which are cheap and are just a line of .1" spaced square posts in a plastic matrix. If one wrapped each lead of an igniter to one of the posts of such a header, then all the connecting could be done to the other ends of posts. And the rigid spacing of the header posts would naturally prevent shorts in the igniter leads.
Those square posts are in fact the same as wire wrap posts. The only diff is that wire wrap posts tend to be longer.

In all likelihood, if you tried to wrap the stiff, steel wire of the ignitor around the post, you'd end up destroying the ignitor by breaking the bridge wire.

It's good you're thinking about it - that's how better techniques evolve. For me, the ideal connector would be some sort of insulated, slide-on sleeve that, like Chinese handcuffs, slides easily onto the ignitor lead, then remains securely attached. I was thinking something along the lines of a 20 gauge socket as found in famale D-sub connectors.

But, even if such an animal existed, it would suffer from the same problems as the alligator clips in a clip whip - after a couple flights, it would likely be so cruddy as to need replacement, which brings us back to lead extensions - ie, disposables instead of re-usables.

Doug

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  #32  
Old 11-14-2008, 11:39 AM
Jeff Walther Jeff Walther is offline
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Quote:
Originally Posted by Doug Sams
But, even if such an animal existed, it would suffer from the same problems as the alligator clips in a clip whip - after a couple flights, it would likely be so cruddy as to need replacement, which brings us back to lead extensions - ie, disposables instead of re-usables.


Yes, the more I learn about this, the more it looks like having some soldered-lead-extended igniters on hand is the soundest solution.

There are pin receptacles for very small gauge wire which might be usable. However, I think the smallest I've seen are about 26 or 28 gauge and I bet the igniter leads are smaller than that. And the crud problem you mention would make it kind of pointless anyway.

Of course, one could keep some steel wool and maybe flux cleaner (nasty solvents) on hand and keep the clips clean, maybe. Part of the problem there is that the igniter leads are so narrow that they can fit across a tiny uncleaned portion of the clip and cause a problem.
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  #33  
Old 11-14-2008, 01:59 PM
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Gus Gus is offline
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Doug,

Wouldn't the simplest solution be to have igniters just like the current Estes or Quest ones, but with leads 3 times as long?

In other words, "Cluster Igniters".

At the manufacturing stage they would be no more complex to make than current igniters, require just a smidge more wire, and could be sold for even more than the ridiculously high priced 6 packs of regular igniters.

Sounds like a good product for Bill Stine, or an Estes lurker to suggest to the boss.
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  #34  
Old 11-14-2008, 02:19 PM
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Originally Posted by Gus
Wouldn't the simplest solution be to have igniters just like the current Estes or Quest ones, but with leads 3 times as long?
Steve,

In brief, yes. For example, compared to 2-wire ignitors from Road Runner or AT's new ones, all you have to do is strip and twist the ends, and you're ready to go. They already have the added length necessary for clustering. (Dave Schaefer did a 7-motor cluster of RoadRunner G80's at LDRS2006, using stock ignitors, and got all 7 lit, IIRC.)

In the case of the Estes ignitors, here are some things to consider. I've never bought a pack of Estes ignitors. (Because of all the staging I do, I have a surplus.) And I can't imagine paying for them above and beyond what I pay for motors with ignitors included. So, given that paradigm, I would anticipate lots of reluctance in the user base, even with longer leads. It already takes me lots of self-arm-twisting to buy a $4.59 pack of toilet pap...er...ejection wadding so ponying up for a pack of Estes ignitors would probably require days of agonizing fretting beforehand

If they simply extended the lead length, there's the issue of insulation. With a couple more inches of wire, insulation is a must to avoid shorting.

And if they use the same stiff, steel wire, there's still the likelihood of damaging the bridge wire when you twist the leads.

So, in brief, yes, but upon further reflection, I see several obstacles to overcome before it's truly workable.

Doug

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  #35  
Old 11-14-2008, 03:05 PM
jbuscaglia jbuscaglia is offline
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Quote:
Originally Posted by Gus
Doug,

Wouldn't the simplest solution be to have igniters just like the current Estes or Quest ones, but with leads 3 times as long?

In other words, "Cluster Igniters".

At the manufacturing stage they would be no more complex to make than current igniters, require just a smidge more wire, and could be sold for even more than the ridiculously high priced 6 packs of regular igniters.

Sounds like a good product for Bill Stine, or an Estes lurker to suggest to the boss.


The leads on the new Quest igniters are quite long. Clustering with them shouldn't require any extensions, unless the motors are spaced very far apart.

Oh, yeah, I forgot to mention that the leads are insulated, too.
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  #36  
Old 11-14-2008, 08:08 PM
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Quote:
Originally Posted by jbuscaglia
The leads on the new Quest igniters are quite long. Clustering with them shouldn't require any extensions, unless the motors are spaced very far apart.

Oh, yeah, I forgot to mention that the leads are insulated, too.
I just got a closer look at those, and yes, they do look much more cluster friendly. The leads look long enough for clusters of three or four motors. I'd prefer them a couple inches longer. That makes larger clusters easier.

But I look forward to trying these. If they're reliable, they'll certainly make things easier.

Doug

[Edit]I got a shipment of Quest motors in this week but tonight was the first chance I had to look at the ignitors that came with.

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Last edited by Doug Sams : 11-14-2008 at 08:45 PM.
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