Hybrids 2024

[ContrailRockets]

Increasing surface area with pleats and twisted ribs etc has yielded massive performance boosts in micro-hybrids, I'm pretty excited to upscale some of the grains I made for micros and try them out with the new 38mm tank when it arrives.

I can only imagine that pleated BG or SP grains would be even more of a performance boost over my ASA grains with that kind of geometry!

The 98mm M-2700 BS has about 113 inches of surface area. The 42 star 98mm Black Smoke grain has over 600 inches of surface area.

 

[kramer714]

yes, yes I am....

So here is the logic, and this is important, I designed this to be able to test motors, flight hardware will be related. but different.

I looking at (3) different grains types for testing plus (1) a baseline

1. Spiral port - 3d printed
2. Spiral port, porous - 'wax' impregnated 3d printed
3. Wax with a 3d printed 'rebar' skeleton
4. BASELINE Schedule 80 PVC

Ok lest start with the motor case, aluminum tube, representative of a real motor tube (not that that is too important for this test configuration), cheep to buy, easy to just cut and square, easy to calculate the pressure capability (remember for a tie rod cylinder, there isn't any axial load JUST hoop)

Sample 1, trying test for the regression rate and also how uniform the burn is. For the initial test I don't want to burn all the way through the grain, i want to see how uniform the grain is eroding. I could just 3d print a larger grain, throw away the OD, or.... use cheep PVC as a liner (call it a spacer) print a smaller OD grain press fit, and test. If I do burn through the grain, I still have the PVC to give me more time. Plus, I can buy PVC pipe cheaper than buying phenolic motor liners.

Sample 2 and Sample 3 For these I plan on using a PVC liner for flight, with the 3d printed parts 'vacuum wax cast' into the PVC. Easy to seal, easy to make. the test motor configuration also lets me get a chance to do some testing of the seal method I plan to use.

Sample 4, just open up the ends of schedule 80 slips right onto the fixture.

Mike (it is hard to be this cheap) K

P.S. one of the bigger challenges for my 50 year old lathe is threading. I was able to use a 3/4 UNF die an make the bottle threads.

Forward ends off the lathe, just need to drill the tie rod and load frame holes.

Per the conversation, the PVC acts as a slow burning insulator with the fast burning grain (not shown) inside it.

Mike K

 

[ContrailRockets]

Forward ends off the lathe, just need to drill the tie rod and load frame holes.

Per the conversation, the PVC acts as a slow burning insulator with the fast burning grain (not shown) inside it.

Mike K
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Is that 1 inch schedule 40 PVC or Home Depot PR-200 which is SDR 21 pipe? SDR 21 is half the price and works great in 38 mm as the liner if you design around your liner burning.
Tom

 

[kramer714]

Is that 1 inch schedule 40 PVC or Home Depot PR-200 which is SDR 21 pipe? SDR 21 is half the price and works great in 38 mm as the liner if you design around your liner burning.
Tom

plus it is pretty easy to seal to...

 

[beeblebrox]

The plan is to fly this at the next MDRA launch in October.

 

[tommd]

The plan is to fly this at the next MDRA launch in October.


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which 3D printer? whats the z height of that grain?

 

[ContrailRockets]

which 3D printer? whats the z height of that grain?

What material are you printing?

 

[P_Carroll2525]

What material are you printing?

Probably ABS or PETG.

 

[cfb_rolley]

Quick question about using flow restrictors for contrail motors. I've mentioned before that 3/16" push to connect fittings are bloody hard to track down here, but 1/4" are really common.

I that led me to think about flow restrictors. For reloads that use 3/16" fittings, would there be any problems with using a 1/4" fitting and hose, but installing a brass bung on the top side of the floating injector with a hole drilled through it to the ID of a 3/16" hose to get the correct flow rate?

 

[OzHybrid]

Quick question about using flow restrictors for contrail motors. I've mentioned before that 3/16" push to connect fittings are bloody hard to track down here, but 1/4" are really That does then change your hybrid into an experimental motorcommon.

I that led me to think about flow restrictors. For reloads that use 3/16" fittings, would there be any problems with using a 1/4" fitting and hose, but installing a brass bung on the top side of the floating injector with a hole drilled through it to the ID of a 3/16" hose to get the correct flow rate?

Or change out to 5mm or 4mm fittings or 6mm with restrictor. That does then make it an experimental motor unless the changes are approved by Contrail.
Tripoli deals with this in range safety distances by saying , paraphrasing, " here's the imperial safety distances, here's the metric,. We know they're not an exact match, but they're close enough"
Over to you Tom....... @ContrailRockets It can be really difficult to get imperial tubing sizes in a Metric country...

 

[cfb_rolley]

That does then make it an experimental motor unless the changes are approved by Contrail.

Yeah this is for my 12" ex motor mainly, I'm pre-empting running out of spare fittings at some point and also allows me to fine-tune the flow for a given grain and nozzle combo. I wouldn't be able to use a CNVA if I'm using a flow restrictor, but fittings for metric hose sizes would get close enough to desired flow rate I reckon.

 

[ContrailRockets]

Quick question about using flow restrictors for contrail motors. I've mentioned before that 3/16" push to connect fittings are bloody hard to track down here, but 1/4" are really common.

I that led me to think about flow restrictors. For reloads that use 3/16" fittings, would there be any problems with using a 1/4" fitting and hose, but installing a brass bung on the top side of the floating injector with a hole drilled through it to the ID of a 3/16" hose to get the correct flow rate?

Yes it is possible to restrict or increase flow using a PTC. On our website we have 3/16 inch PTC at fantastic prices and 3/16 inch fill line as well. Several of our fittings are ported to larger ID to increase flows. The 1/2 PTC has a .375 ID that is machined to a .5 ID. That modification allows us to push two gallons of Nitrous Oxide per second into the combustion chamber. You can see that in the YouTube video of the 98mm N-4000.

 

[ContrailRockets]

Or change out to 5mm or 4mm fittings or 6mm with restrictor. That does then make it an experimental motor unless the changes are approved by Contrail.
Tripoli deals with this in range safety distances by saying , paraphrasing, " here's the imperial safety distances, here's the metric,. We know they're not an exact match, but they're close enough"
Over to you Tom....... @ContrailRockets It can be really difficult to get imperial tubing sizes in a Metric country...

As the hose is burnt out of the injector it becomes the PTC that regulates the flow in combination with the nozzle and the actual combustion process and the increased pressure that regulates flow.
As each Contrail reload comes with a PTC injector and fill line if your modifying injectors that probably means that you’re providing your own fuel grains, which means that you’re probably flying EX, which means Contrail has no say in how you modify injectors.

 

[drewnickel]

Yeah this is for my 12" ex motor mainly, I'm pre-empting running out of spare fittings at some point and also allows me to fine-tune the flow for a given grain and nozzle combo. I wouldn't be able to use a CNVA if I'm using a flow restrictor, but fittings for metric hose sizes would get close enough to desired flow rate I reckon.

May look at doing DOT compression fittings instead of push to connects at that point. The internal tube support in the fitting for a 1/4 inch fitting is around 0.17 inches vs the 3/16 hose's 0.18 inch ID, which equates to a ~10% loss in total area. In tests I ran the DOT compression fittings consistently had higher discharge coefficients than push to connects though, which would likely offset that.

 

[G_T]

So far I'm about 1 for 3 in ratio of PTC fittings that end up blowing their core stub of tube (which is the flow restrictor) sometime during the burn. I'm using 3 in my motor so the effect is not catastrophic.

Gerald

 

[cfb_rolley]

On our website we have 3/16 inch PTC at fantastic prices and 3/16 inch fill line as well.

They are really good prices, So when I've ordered tanks/hardware etc. I generally add a few injectors that I think I'll need. But the exchange rate and shipping to Australia means that buying injectors on their own ends up expensive (unless buying a ton of them at once I guess).

If your modifying injectors that probably means that you’re providing your own fuel grains, which means that you’re probably flying EX, which means Contrail has no say in how you modify injectors.

In the case of the 12" tank I'll be using my own ASA grains, so those flights will be EX either way, but I'll still be using Contrail reloads in the 16" motor. I use injectors as part of a fill hose adapter and sometimes it gets broken, meaning I'm sometimes consuming 2 injectors for the 1 flight so will probably consume enough to run out of spare injectors at some point.

If I was to use a brass restrictor with the 16" motor, I would be using the grain from a certified reload with 1/4" PTC, but adding brass flow restrictor sized to the I.D of the size of hose that the reload designed for.

E.g: For a G-130 reload, I would be using a 1/4" PTC, 1/4" hose with a 0.18" restrictor instead of the 3/16" hose and PTC (or potentially a 1/4" DOT compression fitting instead of a 3/16" PTC as Drewnickel mentioned)

 

[OzHybrid]

As the hose is burnt out of the injector it becomes the PTC that regulates the flow in combination with the nozzle and the actual combustion process and the increased pressure that regulates flow.
As each Contrail reload comes with a PTC injector and fill line if your modifying injectors that probably means that you’re providing your own fuel grains, which means that you’re probably flying EX, which means Contrail has no say in how you modify injectors.

Where is your market based Tom? US or ROTW?
ROTW is pretty much metric. If we were in the US, we'd get $6 overnight shipping. We're not in the $6 overnight shipping zone. Having metric connectors approved would help ROTW.
Asking for a friend...... is there anything you can do to assist?

 

[rocket_troy]

So far I'm about 1 for 3 in ratio of PTC fittings that end up blowing their core stub of tube (which is the flow restrictor) sometime during the burn. I'm using 3 in my motor so the effect is not catastrophic.

Gerald

For disposable internals, I'd recommend the cheap(ish) Chinese 304 SS PTCs (rated to 40 bar but good to 60+).
For non disposable external, I'd only go with the Camozzi 8000 series which just won't fail. Strong, double seal & proper full collet hose retention - not some flimsy punched out of poofteenth brass sheet ferrule thingy.

TP

 

[OzHybrid]

For disposable internals, I'd recommend the cheap(ish) Chinese 304 SS PTCs (rated to 40 bar but good to 60+).
For non disposable external, I'd only go with the Camozzi 8000 series which just won't fail. Strong, double seal & proper full collet hose retention - not some flimsy punched out of poofteenth brass sheet ferrule thingy.

TP

You of course mean gnats bollocks brass thickness. Can't say poofteenth these days mate.

 

[rocket_troy]

You of course mean gnats bollocks brass thickness. Can't say poofteenth these days mate.

... and to think I was about to say bees dyke

TP

 

[ContrailRockets]

They are really good prices, So when I've ordered tanks/hardware etc. I generally add a few injectors that I think I'll need. But the exchange rate and shipping to Australia means that buying injectors on their own ends up expensive (unless buying a ton of them at once I guess).


In the case of the 12" tank I'll be using my own ASA grains, so those flights will be EX either way, but I'll still be using Contrail reloads in the 16" motor. I use injectors as part of a fill hose adapter and sometimes it gets broken, meaning I'm sometimes consuming 2 injectors for the 1 flight so will probably consume enough to run out of spare injectors at some point.

If I was to use a brass restrictor with the 16" motor, I would be using the grain from a certified reload with 1/4" PTC, but adding brass flow restrictor sized to the I.D of the size of hose that the reload designed for.

E.g: For a G-130 reload, I would be using a 1/4" PTC, 1/4" hose with a 0.18" restrictor instead of the 3/16" hose and PTC (or potentially a 1/4" DOT compression fitting instead of a 3/16" PTC as Drewnickel mentioned)

I use to use DOT fittings outside the motor for the fill line. Because of breaking the line off at the fill PTC. Began using a small c clamp on blast deflector and electrical taping the lines to the clamp. Also found that the hose has a smaller ID than the PTC. It is possible to compress the PTC ring and push the hose out from the backside. Wish someone had told me that sooner as I threw away a lot of fittings in the early days. I still prefer PTC fittings over compression but DOT have certain applications.

 

[drewnickel]

I've used DOT fittings internally for injectors a couple of times. Initial hope was they'd be reusable at least a couple dozen times but ended up only being reusable a couple of times. Threads get gunked up from soot and molten/charred plastic and the heat in some longer burning motors can actually melt the brass. For the most part PTCs are easier to deal with for this reason.

 

[ContrailRockets]

Where is your market based Tom? US or ROTW?
ROTW is pretty much metric. If we were in the US, we'd get $6 overnight shipping. We're not in the $6 overnight shipping zone. Having metric connectors approved would help ROTW.
Asking for a friend...... is there anything you can do to assist?

ROTW. The issue is that motors are certified using the US fittings. Our cost for imperial fittings and hoses is higher which would drive up the cost. Many flyers take advantage of the lower price on our site for fittings. We added these parts to our site and many flyers add fittings to reload orders. I know they are making EX reloads but still buy certified reloads to certify flyers. As long as they follow TRA or local codes we are happy to fill orders.

 

[G_T]

I have the fittings from Contrail installed in the injector bulkhead for the next burn. I do think they are a bit higher quality. We'll see how they do, if I can ever get a chance to burn another motor - preferrably a flight.

Gerald

 

[OzHybrid]

I use to use DOT fittings outside the motor for the fill line. Because of breaking the line off at the fill PTC. Began using a small c clamp on blast deflector and electrical taping the lines to the clamp. Also found that the hose has a smaller ID than the PTC. It is possible to compress the PTC ring and push the hose out from the backside. Wish someone had told me that sooner as I threw away a lot of fittings in the early days. I still prefer PTC fittings over compression but DOT have certain applications.

Maybe next time you're getting a motor tested, test one of the existing motors with metric fittings and if the test result is close enough thrust wise, it just becomes a manufacturer approved alternative for that motor. Not sure how that would work. It's a Tripoli motor testing question.
I don't think there's any more money in it selling metric fittings at your end other than at the initial motor sale, just additional good will. But good will also sells more motors and reloads.

 

[cfb_rolley]

good will also sells more motors and reloads.

Tom's support is exactly why I keep wanting to buy from him haha. When I ordered my 12" tank, I forgot to put o-rings on the order, and figured I'd just have to put them on my next order. but when the order arrived, there was a note in the box with a set of o-rings - legend!

There was some talk of setting up a Tripoli Motor Testing facility in Australia not all that long ago - bit of a shower thought right now, but if one was set up here, would it theoretically be possible for someone to do the testing of contrail motors with metric fittings here so that Tom could have it listed as one of the certified combinations of contrail reloads? That'd be a cool collaboration!

 

[OzHybrid]

Tom's support is exactly why I keep wanting to buy from him haha. When I ordered my 12" tank, I forgot to put o-rings on the order, and figured I'd just have to put them on my next order. but when the order arrived, there was a note in the box with a set of o-rings - legend!

There was some talk of setting up a Tripoli Motor Testing facility in Australia not all that long ago - bit of a shower thought right now, but if one was set up here, would it theoretically be possible for someone to do the testing of contrail motors with metric fittings here so that Tom could have it listed as one of the certified combinations of contrail reloads? That'd be a cool collaboration!

I think the request for approval of modifications has to come from the existing manufacturer of the hardware. But that's a Tripoli Motor Testing question.
I believe there was in principle agreement with the previous chair of TMT which approved the possibility of testing in Oz. It was never actually set up.

As there is now a new chair, that would have to be reverified and a testing process agreed. Not sure it's a practical solution in any short term.

 

[cfb_rolley]

Level 1 cert achieved - and MAN it was spectacular! These Contrail HP reloads are bloody awesome!

 

[OzHybrid]

Level 1 cert achieved - and MAN it was spectacular! These Contrail HP reloads are bloody awesome!

View attachment 671553

Congratulations. Who signed you off?

 

[cfb_rolley]

Congratulations. Who signed you off?

Anthony from QRS.