11 replies to this topic

[Karl]

Hi All,

I've been wanting to make some 18mm OD rocket motors to power my models as the cost of Estes is terrible plus it gives me scope to make different power outputs rather than the standard A8, B6 & C6's. Has anyone made these before or know what kind of comps I should be making to get as much power out of the engines as possible?

Cheers,
Karl

[BrightStar]

Hi Karl,

BP end-burners are seemly simple but actually quite difficult to 'dial in'. Estes have them pretty much optimised. To match their performance you'll need a very hot fuel mix, very high quality tubes, preferably a strong press and a good deal of time to experiment.

It can be done however - Ned comes to the rescue once again:

Skylighter - How to make Estes model rocket engines

[Karl]

Cheers Brightstar.

I've followed Ned's tutorial to the word and can't get them dialled in. I've tried using Willow, Pine & Alder charcoal, different durations of milling plus cored & un-cored motors. I can get a 150g rocket 10ft but then the motor drops thrust and brings her back down.

[BrightStar]

I can get a 150g rocket 10ft but then the motor drops thrust and brings her back down.

When I was making 1/2" end burners it took me 7 or 8 tests to get one to a decent height and that was just lifting a thin balsa stick... There's no real short cut, you just have to change one variable at a time until something vaguely works.

I found the diameter of the nozzle to be one of the most critical factors. This needs to be narrower than standard gerb tooling to generate any decent thrust. What size aperture are you using?

[dr thrust]

i found this page on the matter , with a cutaway of a c6 motor with the nozzle design, do you have tooling? and as you know estes motors are pressed under a very large load,in production for repeatability.

Edited by dr thrust, 21 October 2010 - 10:24 PM.

[Karl]

Yep I have tooling and have tried both 4mm and 5mm core & end burners.

Cheers for the link Chris.

[dr thrust]

how long was the core? ive used willow bp with kick ass results in nozzle-less motors, abiet with a 6" core. could you not make your motor a tad longer and increase the core?
just a thought how much can a d motor lift, 128g?,.
hmm edit, just converted the measurement of the nozzle on the link,0.118" = a 3mm! nozzle your 1mm out

Edited by chris m, 10 August 2010 - 11:29 PM.

[icarus]

if you inspect the nozzle after firing the hole is often bigger erosion causing variable performance has anyone any good nozzle formulations for long burn time end burners??

[Potassium chlorate]

if you inspect the nozzle after firing the hole is often bigger erosion causing variable performance has anyone any good nozzle formulations for long burn time end burners??

http://www.flashnet.dk/rts/

Though I prefer coreburners, made with a proper spindle:

http://www.youtube.com/watch?v=0PkVYY-6S8U

My only problem is to balance them with the right stick, but that will come in time. I have made some 3/4" or 4oz or what they are called in Anglo-Saxon countries as well, but I won't upload anything before I get a straight flight. But the burning is no problem with a coreburner and good BP.

[vaslop2005]

for me, I use 1:4.16 ratio of ID to nozzle, so in other words, divide the ID by 4.16 and you'll have the nozzle diameter. This is used with my ballmilled 72:14:14 pine black powder (strange I know, but any fast black powder formula works really)

everyone has their own way of doing things, but that's mine, hope it helps

[dr thrust]

if you inspect the nozzle after firing the hole is often bigger erosion causing variable performance has anyone any good nozzle formulations for long burn time end burners??

theres all manner of things to try like, grinding up the wife's terracotta plant pots and adding this to bentonite,or powdered graphite added to bentonite to aid spindle release, and stop heat erosion.
so much so that the heat reflected back off the top of the nozzle and burned out the tube wall, leading me to change the chamfer on the base of my no 1 rammer to a sharper 35 degees

[Pyro.1]

just a thought how much can a d motor lift, 128g?,.

D12-3 single stage will lift 14oz or 396.2g
D12-5 single stage will lift 10oz or 283g

Paul

Edited by Pyro.1, 17 November 2010 - 08:53 PM.