Using A D Engine Casing As A B/C Engine Motor Mount.

Anybody used a D engine casing as a B/C size engine motor mount?

I've got the pieces parts to fabricate a mount, but just wondering what you've done, or would do.

I'd like to do some testing with lower powered engines before using the D12-5.

As always, thanks for your advice and thoughts.

lakeroadster said:

Anybody used a D engine casing as a B/C size engine motor mount?

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Too heavy.

If D is as high as you will ever go, just grab an 18mm AT RMS 18/20 motor, and fly D's with it:
https://www.csrocketry.com/rocket-motors/aerotech-rocketry/hardware/18mm/18-20-hardware.html

Both BT (blue thunder) and WL (white lighting) motors are available:
https://www.csrocketry.com/rocket-motors/aerotech-rocketry/motors/18mm/18-20-reloads.html
https://www.siriusrocketry.biz/isho...rms-reload-kits-45/rms-18-20-reload-kits-185/

On the other hand, if you stick a 24mm motor mount in there, you could crank it upto F....
:tongue:

lakeroadster said:

Anybody used a D engine casing as a B/C size engine motor mount?

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afadeev said:

Too heavy....

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I'm an old Hot Rodder. I can drill lightening holes in it to reduce the weight.. like the front axle on my Model T :wink:

https://bellevillehobby.com/product/standard-to-d-engine-adapter/



Centuri Thunder ROC (a D Convertible kit) came with a C engine adapter to fit in the 24mm D engine mount, you can make your own: (you might be able to cut the centering rings from the spent D engine casing, this will reduce weight compared to using the entire casing)

https://www.spacemodeling.org/jimz/cen5340.htm

Sure I have done it several times, but as others have said they are heavy. I usually use 24mm motor casings to make BT50 to BT20 centering rings by cutting slices off the ends and peeling a layer or two ofbpaper from the ID.

afadeev said:

Too heavy.

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The rocket already has a 24mm mount, he wants to use a smaller motor for first flight. From the pic of the rocket, probably not too heavy. You can use a D casing for an adapter to a C6-3. The new Quest C and D motors sound like they will be perfect for this application

I've done it before as well. In a pinch, it can work, but adds a lot of weight at the aft end so make sure it's still stable with the new CG and lower thrust motor.

I did that once when flying my 24mm Quinstar on a C6. For general rocket use, though, to keep weight down I'm ordering up some of the Estes red plastic adapters. I expect that for some of my smaller 24mm designs I'll be wanting to try the QuestJet C and D motors (once available).

Those red plastic adapters wear out/melt, scorch/burn all too quickly. Once you clean out a D motor casing you are only dealing with 11g or 0.40 oz of weight. That's not all that bad. I have both types in my range box and more often than not, I'll use the D casing over the plastic ones. Never seen them cause any stability issues. So in my opinion, the weigh factor is negligible.

Hmm, noted. I'm gonna give them a try anyway, don't expect to use them a lot so if they don't last long no biggie. I like that they provide positive retention of the motor.

Thinking about the original question, if a rocket is stable with a D12, then I supposed it ought be stable with a D12 case wrapped around a much lighter C6 (although I haven't worked the numbers). So maybe weight really isn't a big issue here.

Really depends. Maybe no big deal for a 4 oz 3FNC rocket, but for a heavy, draggy, weather-vane like an X-wing, the speed at end of the launch rod may be pretty important, more so than a theoretical apogee. This one is beyond my mind-sim. But there may be a big difference between 4 oz total weight and 4.5 oz on a rocket like this when loaded with a lower thrust C engine. I would suggest if you have the right amount of nose weight for the D engine, make a portion of it removeable when flying with the C engine so you have just enough for stability and not to put you over the lift-off weight limit for the C engine.

Thanks guys. Lot's of great input, as usual.

I'll run some simulations in, Open Rocket, on the following and see how she flies.

• Custom engine mount adapter, as shown below,
• D-Engine spent casing,
• D-Engine spent casing swiss cheesed by drilling lightening holes,
• The plastic adapter mount.

GlenP said:

... a ..... weather-vane like an X-wing.

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I think the Open Rocket simulations should be accurate in regard to speed at the tip of the launch rod....

But In Your Opinion, should I be extra cautious in regard to wind speeds at launch?

Thanks for your tutelage.

The angle of attack at the end of the rod will be determined by the horizontal wind speed and the vertical speed of the rocket. A ratio of wind:rocket speed of 1:10 would be about 5-deg angle of attack. I would not want to see any more than that on this kind of rocket, but your experience may find this to be overly cautious. But, my hesitation is somewhat clouded by impressions of the old Estes heavy plastic X-wings, yours may actually be considerably lighter, although still fairly draggy. The more it turns into the horizontal wind, the less vertical altitude you will get, and less time for your recovery to deploy and function as intended.

I am cheap.
Take a roll of masking tape and an exacto knife.
With the tape still on the roll, divide it into thirds width wise and cut AROUND the roll, dividing it into strips a third of the width of the original tape.
Cut a BT20 long enough for your engine, add an engine block (I just cut a 1/4” strip off the BT20, nest it inside and glue it in. Have yet to have it fail. You can even put an engine hook in.

Use the masking tape to create centering rings, just keep wrapping around and test fitting until it fits in your BT-50. If you use an engine hook, put the tape on forward enough to still allow some spring.

Seal the tape with thin CA. It may swell a bit and need to be sanded down.

Anyhoo, I use these 1/3 masking tape strips to make centering rings a lot.

Hope this helps

Oh yeah, and it is also easier and less messy than trying to cut up a D casing

BABAR said:

I am cheap.

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Me too. I'm retired. The saying "Time Is Money" no longer applies.

I remember my grandfather saying that my grandmother had their entire home patched together with duct tape.... and I also remember the fellas in Apollo 13 building carbon air filter scrubber cartridge adapters from tape also.

Everything old.... is new again.

I do appreciate everyone's input.

This site is pretty awesome.... :blush:

Yes it will work fine, just make sure you remove the nozzle and use some sort of engine block.

lakeroadster said:

Thanks guys. Lot's of great input, as usual.

I'll run some simulations in, Open Rocket, on the following and see how she flies.

• Custom engine mount adapter, as shown below, Yields
• D-Engine spent casing,
• D-Engine spent casing swiss cheesed by drilling lightening holes,
• The plastic adapter mount.

I think the Open Rocket simulations should be accurate in regard to speed at the tip of the launch rod....

But In Your Opinion, should I be extra cautious in regard to wind speeds at launch?

Thanks for your tutelage.

Click to expand...

Compilation of Data from Open Rocket Simulations Shown Below

You don;t need to remove the nozzle. Just enlarge the nozzle hole and leave the outside portion of the nozzle clay which will BE the motor block (no need to remove the nozzle and then glue in a motor block.

The Estes adapters are SOOOOO much better and SOOOO inexpensive and SOOOO reusable.

dwinings said:

Yes it will work fine, just make sure you remove the nozzle and use some sort of engine block.

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shreadvector said:

The Estes adapters are SOOOOO much better and SOOOO inexpensive and SOOOO reusable.

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NOT so reusable as one might want to believe. I have 3 in my range box and all of them are on their last legs with probably 3 uses each. They're all warped, burned and melting where the nozzle was. They get pretty hot which causes any tape you may have used for friction fitting to melt and if you by chance don't get it out immediately after using, can and will glue itself in the motor mount. The spent D casings are a little more heat friendly and if you really don't mind going the distance, make your own. I have 3-4 each 13mm to 18mm homemade adapters and 3-4 20/50 homemade adapters using those 20/50 spiral wound CR's, aka engine blocks, and regular tubes which have worked pretty well. Best the treat these with CA or something though. They do tend to wear out.

Not saying it can't happen, but I've never seen the 18mm and 24mm Estes Motor adapters melt. If you don't use the orange spacer when using a short motor in the 29mm adapter, the top of it will in fact melt. I've also never used these adapters with Quest motors that seam to run a little hotter. I've test fired each case at least 20 times without any distortion at all. I can see the nozzle side of the adapter melt if you have the habit of letting it rest directly on the blast deflector plate. I always raise my models a couple inches to protect the rear of the models.

John Boren

I agree with these observations and will add one more that we saw when a scout "leader" put his min-motors into the 13/18mm adapter with the nozzle pointing the wrong way. He threaded the starter up through the long ejection taper section thinking it was a fancy nozzle extender. The result was 75% less thrust and model falling out of the sky as soon as they left the 4 foot launch rods. We were afraid we had bulk packs of 1/2A3-4T motors with drastically less propellant than they should have ... UNTIL we grabbed one off the ground and saw that it was installed wrong. Pointed it out to the "leader" and the rest of the flights were fine. The ones that had the motors firing through the ejection cone were slightly melted.

And the 24mm motors like the E15, E20, E30 work just fine in the 24/29mm adapter with no melting (when you use the orange spacer).

JumpJet said:

Not saying it can't happen, but I've never seen the 18mm and 24mm Estes Motor adapters melt. If you don't use the orange spacer when using a short motor in the 29mm adapter, the top of it will in fact melt. I've also never used these adapters with Quest motors that seam to run a little hotter. I've test fired each case at least 20 times without any distortion at all. I can see the nozzle side of the adapter melt if you have the habit of letting it rest directly on the blast deflector plate. I always raise my models a couple inches to protect the rear of the models.

John Boren

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We have been using the 29/24 adapters to fly my son's Super Big Bertha on D12-3 motors. We have flown four times so far with no melting forward or aft.

I ended up building an adapter...

lakeroadster said:

I ended up building an adapter...

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Go you! Probably had everything you needed on hand anyway. I'm all about making something myself instead of buying it. Especially if I keep it in stock. And I do have ample stock. Your MM looks great. I have more respect for someone that will craft a thing than taking the easy way out.

Gary Byrum said:

Go you!

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Thanks.

For me rocketry is a 90 / 10 affair. The designing and building is 90% of the fun / challenge. Launching the rocket is 10%.

Guess that's why I'm a scratch builder. :wink:

lakeroadster said:

Thanks.

For me rocketry is a 90 / 10 affair. The designing and building is 90% of the fun / challenge. Launching the rocket is 10%.

Guess that's why I'm a scratch builder. :wink:

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My percentages are pretty identical. I always have designs to pick and choose from because I'm always designing. The maiden flight covers that 10% for the most part. It'll determine whether or not I got it right. If it fails, back to the drawing board. If it flies as expected, it MIGHT get a few more flights in before I'm ready to move on to the next batch of builds. It's no wonder I have a home invasion going on here. I have rockets out the wazoo!

afadeev said:

...
On the other hand, if you stick a 24mm motor mount in there, you could crank it upto F....
:tongue:

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No need to stop at F. You can go all the way to 89% G on CTI 24mm if you don't have a block and you have enough body tube. A G127 red is just what the doctor ordered for this build, amirite?

https://pro38.com/products/pro24/motor.php

Gary Byrum said:

My percentages are pretty identical. I always have designs to pick and choose from because I'm always designing. The maiden flight covers that 10% for the most part. It'll determine whether or not I got it right. If it fails, back to the drawing board. If it flies as expected, it MIGHT get a few more flights in before I'm ready to move on to the next batch of builds. It's no wonder I have a home invasion going on here. I have rockets out the wazoo!

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That pretty much nails it for me too.

lakeroadster said:

...The designing and building is 90% of the fun / challenge. Launching the rocket is 10%...

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Sounds about right for the typical single-stage chute/streamer recovery, but for some types of rockets, more interesting things can happen during launch and recovery: clusters, multi-stage, parallel-stage, rotor, glider, R/C glider, or combinations thereof, the flights can be pretty fun and impressive too. And, on-board video, electronics, etc... might bump up the fun of the flying part to 20%, at least... But, yeah, lately I have been doing more building than flying.

boatgeek said:

No need to stop at F. You can go all the way to 89% G on CTI 24mm if you don't have a block and you have enough body tube. A G127 red is just what the doctor ordered for this build, amirite?

https://pro38.com/products/pro24/motor.php

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A 6 grain Cesaroni motor would be spectacular, to be sure. But I think lakeroadster is looking for a long term relationship with his X-wing, rather than a one night stand. The only reason I've never used Cesaroni motors is that darn Hazmat fee. Our club does not have a big membership where we can combine orders and spread the fee. So I'll continue using AT RMS and LMS motors, and save the money.