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-   -   Initial Motor Requests (http://www.oldrocketforum.com/showthread.php?t=1364)

Mark+3 01-05-2007 04:48 PM

Initial Motor Requests
 
What motors would everyone like to see Semroc release first?

Carl: "The order of release will be based on discussions here. The smaller 18mm and under machine is being built first. Engines over 70mm long or over 18mm in diameter will be done on the larger machine."

Carl: "The absence of 1/2A and A boosters is a good example of why there is little new or innovative kits to use low power boosters. The places available to fly two-stage rockets with a minimum of a C6-0 is growing smaller all the time. If the C6 was a C12 or C20, at least you could do low altitude two-stage rockets with heavier designs. That is just my opinion. I always liked two-stage rockets that you could see and recover. I also liked the B14-0 because I could make the rocket a little heavier."

13mm 1/2A and A boosters, 18mm A and B power boosters are first on my wish list.
Obviously the B-14 is in high demand as I don't believe a day goes by that someone doesn't publicly mourn it's absence

Royatl 01-05-2007 06:13 PM

Quote:
Originally Posted by Mark+3
What motors would everyone like to see Semroc release first?13mm 1/2A and A boosters, 18mm A and B power boosters are first on my wish list.
Obviously the B-14 is in high demand as I don't believe a day goes by that someone doesn't publicly mourn it's absence


Definitely with the 13mm motors. I'd like to be able to fly the Fire Fly! and I'd like to be able to build and fly a Midget.

CPMcGraw 01-05-2007 06:18 PM

I highly agree -- 13mm boosters, 18mm A and B boosters, and better variety of power choices among both 13mm and 18mm A and B single-stage motors. "C" class is nice, but I'm not able to take advantage of them as much where I fly.

Doug Sams 01-05-2007 06:24 PM

Quote:
Originally Posted by Mark+3
What motors would everyone like to see Semroc release first?
While making motors equivalent to the commonly available, medium thrust motors already out there makes sense in the long run, I'd say that the differentiated products should be first. 29mm cored BP motors - woo hoo! I never go to play with any of these (eg, F100, et al) but I am chomping at the bit.

Likewise, I want to see cored 24mm versions, too. D30, E40. In 18mm, a C20 to go with the B14 (if it's possible...to fit in that much impulse/powder along with a deep core).

If the reliability problems of cored motors can be solved/avoided, then it's possible to position these fast burn/high thrust motors against medium thrust motors. IOW, almost any rocket than can fly on a B6-6 can fly on a B14-6 without adverse consequences. So a high thrust motor can be sold into mainstream applications as well as heavy lift.

OTOH, while low thrust motors are fun, they can't cross over into medium thrust applications without lots of complaints and/or warrany claims. So the high thrust motors should have the best potential for getting a return on investment in a timely fashion. IOW, save the low-thrust and medium thrust motors for later.

I wonder about reliability and cost. I've heard that some large BP motors had fiberglass cases. If that's what it takes, then I wonder if the added cost will pose retail price problems. I'm willing to pay extra, but I worry about others.

Seeing Carl's old catalog along with the AVI motors, the idea of adjustable delays is stuck in my head. If I understand it correctly, a booster motor plus DECAP makes a delay motor, right? Will it be possible for the user to trim the delay before gluing it in? Will it even be sold in pieces to allow that?

The potential beauty of this is that only two pieces are required (plus glue) to make a myriad of delay options. Looking at Aerotech thru an accountant's eyes, I was able to learn the huge costs they have tied up in delays and delay spacers. They have over 20 of each for their 29 and 38mm motors. Cesaroni has 1. They use the same delay grain in all 38's and (I think) 54's. It may be 13 secs in one motor and a 15 in another, but it's the same delay. 1 inventory item. (BTW, with BP motors, there will be no variations due to motor burn pressure since the delays don't light until motor burnout.)

From a manufacturing perspective, delay grains would be cranked out along with 0 delay motors. Advanced users - us - would buy these two piece motors and use them however we need - eg, C20-0, C20-5, C20-10. But ordinary retail channels can be served with pre-trimmed, pre-glued products as well. However, these would be built up using the same two pieces. There would be no large factory inventories of pre-trimmed, pre-glued motors.

Again, I'm not sure it's possible to build a trimmable delay for BP motors. One experiment I have yet to try is gluing an AT delay into a BP booster motor. If it will light, then it will be possible to trim custom delays with that method. I do wonder if having an APCP delay and BP together poses any sore of shelf life issues.

I also wonder about assembly issues. There needs to be a way to reliably glue the delay in without getting glue on the delay face while getting a good seal around the delay.

Anyway, the idea of a universal motor-delay combo is very tantalizing. There's a potential for having wide variety without proliferation of parts/part numbers.

So, in summary, I'll take:

29mm F100-adj
24mm E40-adj
24mm D30-adj
18mm C20-adj
18mm B14-adj
13mm 1/2A8-0T

Doug

Mark+3 01-05-2007 06:54 PM

Quote:
Originally Posted by Doug Sams
I'd say that the differentiated products should be first. 29mm cored BP motors - woo hoo!

Likewise, I want to see cored 24mm versions, too. D30, E40.


Per Carl: " The smaller 18mm and under machine is being built first. Engines over 70mm long or over 18mm in diameter will be done on the larger machine."

billspad 01-05-2007 10:43 PM

Quote:
Originally Posted by Doug Sams
Again, I'm not sure it's possible to build a trimmable delay for BP motors. One experiment I have yet to try is gluing an AT delay into a BP booster motor. If it will light, then it will be possible to trim custom delays with that method. I do wonder if having an APCP delay and BP together poses any sore of shelf life issues.

Doug


You're going to have to cut it really short. Most of the delay element is burned while an APCP motor is burning. What's left burns at something like 1/32" per second so you're going to have a thin piece of rubbery stuff that's going to need a bulkhead to keep it from blowing out too soon. What you end up with may work but I think Carl's DECAP system is a lot simpler.

Eagle3 01-05-2007 10:46 PM

Quote:
Originally Posted by Doug Sams
... 29mm cored BP motors - woo hoo! I never go to play with any of these (eg, F100, et al) but I am chomping at the bit.


The Rocketflite 29mm G100 is one of the most kick ass motors I've ever used. It was definitely jaw dropping. :)

Carl@Semroc 01-05-2007 10:48 PM

Good input! This is very well received. As I said, the first step is to get a large enough list to get started, get the list approved, then be able to ship samples for testing.

How about any other different sizes? The 15mm will probably be removed. It just does not have too many good uses.

About the port burning C engines, we did have a 3/4C19 that was reliable in testing, but the full C was too much to drill. Maybe if it was done in two operations... In any case, it would be closer to a C32 with the same .3 second burn. Peak thrust of 60 N - 13 pounds. That looks like too much warranty work! >400G's in a Sky Hook!

Carl@Semroc 01-05-2007 10:52 PM

Quote:
Originally Posted by billspad
You're going to have to cut it really short. Most of the delay element is burned while an APCP motor is burning. What's left burns at something like 1/32" per second so you're going to have a thin piece of rubbery stuff that's going to need a bulkhead to keep it from blowing out too soon. What you end up with may work but I think Carl's DECAP system is a lot simpler.
BP delay burns at about .05"/sec so it may be a little easier to trim than the BJ delays. But, I don't think we will release trim directions. I am not comfortable with 14 year olds drilling Black Powder. With every delay from 2-9 seconds available, there is not as much need to modify one to get a particular delay.

Eagle3 01-05-2007 10:54 PM

Quote:
Originally Posted by Carl@Semroc
Good input! This is very well received. As I said, the first step is to get a large enough list to get started, get the list approved, then be able to ship samples for testing.

How about any other different sizes? The 15mm will probably be removed. It just does not have too many good uses.

About the port burning C engines, we did have a 3/4C19 that was reliable in testing, but the full C was too much to drill. Maybe if it was done in two operations... In any case, it would be closer to a C32 with the same .3 second burn. Peak thrust of 60 N - 13 pounds. That looks like too much warranty work! >400G's in a Sky Hook!


Imagine clustering 3 of those C32's! <BG>

I guess I would suggest waiting on the 15mm until after the 10, 13, 18mm line. Then see if there is a real need/interest?

*still thinking about port burning C's* :D Imagine a Cobra or Ranger on 3xC19's!


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