Best General Purpose Motors - is there such a thing?

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soopirV

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Hi- I am well aware that I'm potentially creating a flame-war, not my intent! What I'm hoping to do is learn from others about motor selection. I have (or will have, am in the process of building two kits) 2 54mm kits: MadCow Frenzy that I glassed (100oz final weight) with DD option, and a Rocketry Warehouse Adventurer 3 (projected final weight of about 140-160 oz, 112oz of which is kit weight). I also have 2 38mm kits- a modified (stretched Norad Pro Maxx) and a Madcow AGM-pike. While I haven't built the pike yet, both of the 38 kits should't be far apart, weight wise.
i heard that a vendor will be joining us at our local club launch (a sad rarity), and want to be able to stock up appropriately. What sage wisdom exists on this forum that can help a buyer like me? My criteria
0) Must be CTI - I have chosen to invest in CTI hardware, and am happy with my decision.:
1) what ever I buy has to work in as many rockets as possible (obviously a 54mm load is not going to work in a 38, but maybe vice versa is possible?)
2) the strongest load in my lightest rocket has to stay below waiver, 6500'
3) I hope to be L2 certified Sunday, so I can buy reloads up to L class, but the majority of my flying will be less than that.

Is there an equation or sensibility that applies to situations like this? I'd love to pack in the different flame profile of the CTI loads, but at the same time, I'm not sure I'm going to have time to sim out the entire assortment prior to launch!

Thanks!
Dave
 
Do you already have the hardware or is that part of the question? Are you trying to economize?

If I were buying everything --- hardware and motors --- and I wanted to pay for the least amount of hardware and get a selection of motors that would work for all the rockets, I'd do it by determining the minimums and maximums and working with what was left.

You can't fit a 54mm motor in a 38mm hole, so you would need 38mm hardware and a 38/54 adapter.

What is the minimum thrust required to fly the largest rocket? Checking the selection of Pro38 reloads, what grain size would that thrust generally start at for the kinds of motors you like? Maybe the 3 grain motors have a good selection and there aren't very many 2 grains that fit the bill. 3 grain might be your minimum.

What is the maximum impulse that will keep your lightest rocket under the waiver? What is the largest grain size of Pro38 reload that has a large number of motors in that impulse or lower? Maybe it's 5 grain, and the 6 grains are mostly too big. 5 grain might be your max.

If that were the case, then you might want to get a 5 grain case and two spacers, and you'd have the option to pick from among all the 3, 4, and 5 grain motors, double-checking that none of them fell outside your parameters. Or just get the 4 grain case and no spacers, and be pretty sure most 4 grains would work for something in the fleet.

That's the kind of thought process I would use. Hopefully that helps. I'm not completely certain I was working the exact problem you were asking about...
 
Last edited:
Do you use OpenRocket or RocSim? I think a lot of your questions could be answered if you played around with either of those programs, and simulated the flight of your rockets. You can get a feel for how your rockets will perform and choose what sort of flight profile you want, including critical things like estimates of take-off speed, thrust-to-weight ratio, delay-to-apogee, and altitude at apogee.
 
mid sized K's (~1700 N/s)will put those 54mm birds around 7,000'. I'd shoot for a bunch of fullish J's and possibly a baby K here and there.
 
soopirV said:
Hi- I am well aware that I'm potentially creating a flame-war, not my intent! What I'm hoping to do is learn from others about motor selection. I have (or will have, am in the process of building two kits) 2 54mm kits: MadCow Frenzy that I glassed (100oz final weight) with DD option, and a Rocketry Warehouse Adventurer 3 (projected final weight of about 140-160 oz, 112oz of which is kit weight). I also have 2 38mm kits- a modified (stretched Norad Pro Maxx) and a Madcow AGM-pike. While I haven't built the pike yet, both of the 38 kits should't be far apart, weight wise.
i heard that a vendor will be joining us at our local club launch (a sad rarity), and want to be able to stock up appropriately. What sage wisdom exists on this forum that can help a buyer like me? My criteria
0) Must be CTI - I have chosen to invest in CTI hardware, and am happy with my decision.:
1) what ever I buy has to work in as many rockets as possible (obviously a 54mm load is not going to work in a 38, but maybe vice versa is possible?)
2) the strongest load in my lightest rocket has to stay below waiver, 6500'
3) I hope to be L2 certified Sunday, so I can buy reloads up to L class, but the majority of my flying will be less than that.

Is there an equation or sensibility that applies to situations like this? I'd love to pack in the different flame profile of the CTI loads, but at the same time, I'm not sure I'm going to have time to sim out the entire assortment prior to launch!

Thanks!
Dave
Click to expand...

Best general purpose? Hah, any given white lightning motor of the appropriate impulse!

Sounds like you have previously decided the other way, though. If you are not yet L2 get a large 38mm or small 54mm from Cesaroni for free with your first reload. Red, green, smokey, pink, white, thunder, and classic will all be good general purpose thrust curves. Heck even skidmarks are mostly visual effect. Blue thunder, blue streak, black jack, yellow, vmax, and W9 are where they start getting outside the norm.

I bet you are going to have to taylor motors per rocket more than you suggest above, especially if you are talking about keeping a Norad Pro under 6500 feet. A 38mm J pushed my Nuke Pro to near 8000 feet.

The nice Aeropack 54mm to 38mm adaptor is recommended; you can get cheaper adaptors but I like peace of mind when dealer with this level of power. I plan on flying a lot of the longer 38mm motors in my 54mm rockets, to save some money if nothing else!
 
soopirV said:
Hi- I am well aware that I'm potentially creating a flame-war, not my intent! What I'm hoping to do is learn from others about motor selection. I have (or will have, am in the process of building two kits) 2 54mm kits: MadCow Frenzy that I glassed (100oz final weight) with DD option, and a Rocketry Warehouse Adventurer 3 (projected final weight of about 140-160 oz, 112oz of which is kit weight). I also have 2 38mm kits- a modified (stretched Norad Pro Maxx) and a Madcow AGM-pike. While I haven't built the pike yet, both of the 38 kits should't be far apart, weight wise.
i heard that a vendor will be joining us at our local club launch (a sad rarity), and want to be able to stock up appropriately. What sage wisdom exists on this forum that can help a buyer like me? My criteria
0) Must be CTI - I have chosen to invest in CTI hardware, and am happy with my decision.:
1) what ever I buy has to work in as many rockets as possible (obviously a 54mm load is not going to work in a 38, but maybe vice versa is possible?)
2) the strongest load in my lightest rocket has to stay below waiver, 6500'
3) I hope to be L2 certified Sunday, so I can buy reloads up to L class, but the majority of my flying will be less than that.

Is there an equation or sensibility that applies to situations like this? I'd love to pack in the different flame profile of the CTI loads, but at the same time, I'm not sure I'm going to have time to sim out the entire assortment prior to launch!

Thanks!
Dave
Click to expand...
Go to the motor guide at thrustcurve.org and type in your rocket diameter, dry weight, motor diameter, and maximum casing length, specify CTI, and run the guide for all motors. Download the CSV file with the results. If the rocket has a 54 mm motor mount, add the extra weight od a 54/38 adapter and repeat for 38 mm motors

Now you have the results you seek.

Bob
 
bobkrech said:
Go to the motor guide at thrustcurve.org and type in your rocket diameter, dry weight, motor diameter, and maximum casing length, specify CTI, and run the guide for all motors. Download the CSV file with the results. If the rocket has a 54 mm motor mount, add the extra weight od a 54/38 adapter and repeat for 38 mm motors

Now you have the results you seek.

Bob
Click to expand...

+1. You didn't say what kind of waiver you have... that may ultimately be the #1 factor in selecting your motor.
 
watermelonman said:
Best general purpose? Hah, any given white lightning motor of the appropriate impulse!

Sounds like you have previously decided the other way, though. If you are not yet L2 get a large 38mm or small 54mm from Cesaroni for free with your first reload. Red, green, smokey, pink, white, thunder, and classic will all be good general purpose thrust curves. Heck even skidmarks are mostly visual effect. Blue thunder, blue streak, black jack, yellow, vmax, and W9 are where they start getting outside the norm.

I bet you are going to have to taylor motors per rocket more than you suggest above, especially if you are talking about keeping a Norad Pro under 6500 feet. A 38mm J pushed my Nuke Pro to near 8000 feet.

The nice Aeropack 54mm to 38mm adaptor is recommended; you can get cheaper adaptors but I like peace of mind when dealer with this level of power. I plan on flying a lot of the longer 38mm motors in my 54mm rockets, to save some money if nothing else!
Click to expand...

Definitely agree, and you may want to think about getting higher thrust motors like White Thunder simply because a faster burning I or J will lift the larger rockets and the Norad, while a slower burn may only lift the Norad. My "go to" propellent is now Blue Streak, which has a bit more thrust than whites and reds, but less the Blue Thunder or White thunder. Plus I like the color:)
 
Hi, As Bob said, Thrustcurve.org will give you a good quick overview.
Also take in to account the launch parameters that Thrustcurve uses:
"These simulations were run with a launch guide length of 10ft (rod, rail or
tower). If this is not correct, launch guide lengths can be specified for your saved rockets. (The minimum velocity
required is approximately 15m/s or 50ft/s.) are for a ten launch rail-rod"
From the NAR report:Launching Safely in the 21st Century
October 29, 2005
Recommended Changes to Codes
8.1. NFPA Code 1127
Safe Liftoff
Current text:
4.12.1 A high power rocket shall be launched from a stable device that provides rigid
guidance until the rocket has attained a speed that ensures a predictable flight path.

 Proposed text: Add 4.12.1.1 When the wind at launch exceeds 5 miles per hour, the launch
guidance device shall be of a length to ensure that the rocket reaches a speed of at least four
times the wind speed before its departure from the device."

Be aware that the 6500 agl ceiling is a MAXIMUM depending on conditions and the RSO's judgement, at the time of any given launch!
I would suggest from past experiences, that when you are getting within 10% to 15% of the wavier that you talk to the RSO ahead of time.
Hope to see you Sunday.
 
SCrocketfan said:
Definitely agree, and you may want to think about getting higher thrust motors like White Thunder simply because a faster burning I or J will lift the larger rockets and the Norad, while a slower burn may only lift the Norad. My "go to" propellent is now Blue Streak, which has a bit more thrust than whites and reds, but less the Blue Thunder or White thunder. Plus I like the color:)
Click to expand...

Hah, I should have looked at a thunder thrust curve before piping up! I had no idea they were so upfront. Listen to him instead of me on Cesaroni propellants! Although I think my general purpose list was fine except remove the thunder.

SCrocketfan, if you like blue streak keep an eye out for my inaugural Punisher flight, it will be a J595! Except the kit is not doing a good job of assembling itself these days.
 
Here are all the CTI propellents I know of, arranged in semi-order of burn rate:

Mellow
Imax (for small motors, it's fairly low thrust but for longer grain configurations it can actually be quite fast like the I204, J530, L935, M2245)
Classic
Green3
White
Skidmark
Red Lightning
Smoky sam (in 29mm it can be actually much faster like Imax)
Blue Streak
White Thunder
Vmax

Wow CTI has a lot of different propellents! It's very cool to have so many options though.
 
rfjustin said:
Get yourself a CTI Pro 38 starter set which contains a (3) grain case, (6) grain case, two spacers, and a delay adjustment tool. Everything you need for L1 and L2 flying. When you are ready to step up to 54mm, get the Pro 54 starter set. :)

https://www.apogeerockets.com/Rocke...gs/Cesaroni_38mm_Reloadable_Motor_Starter_Set

https://www.wildmanrocketry.com/ProductDetail.aspx?product=2786
Click to expand...
+ 1 on that strategy. :cheers: Reloads are a one-time thing but casings are forever. :cool2: (unless you loose them). :cry:

Bob
 
Don't bother with the pro38 starter kit. That will get you down to a 1-grain G motor with spacers. Get the free hardware with your L2 reload and get a 5 or 6 grain Pro38 for free. Buy 2 spacers, they're cheap. That will get you down to 3-grain H motors in the 5 grain case, or 4-grain I in the 6.

Get/make a38 to 54mm motor adapter for your 54mm birds. Now you're covered for everything.

The nice thing about the 38 motors is they don't need an aft closure, unlike the 54 hardware. That makes them even simpler.
 
gsquared said:
Don't bother with the pro38 starter kit. That will get you down to a 1-grain G motor with spacers. Get the free hardware with your L2 reload and get a 5 or 6 grain Pro38 for free. Buy 2 spacers, they're cheap. That will get you down to 3-grain H motors in the 5 grain case, or 4-grain I in the 6.

Get/make a38 to 54mm motor adapter for your 54mm birds. Now you're covered for everything.

The nice thing about the 38 motors is they don't need an aft closure, unlike the 54 hardware. That makes them even simpler.
Click to expand...

THe worst part about 38 motors is that they don't need an aft closure, so overexcited people torch their rockets.
 
CarVac said:
THe worst part about 38 motors is that they don't need an aft closure, so overexcited people torch their rockets.
Click to expand...
As in putting the load in the rocket without a case, or cross-threading the disposable closure?
 
If you're looking at a CTI starter set, I'd suggest checking out Performance Hobbies' "Pro38 Level One/Two XL Hardware Package" (first link on this page), but check with them first. I believe Ken is changing-out the 3G case mentioned in the description for a 4G case (not sure if that affects the price yet), which lets you fly all of the 2G/3G/4G and 5G/6G/6GXL Pro38 reloads using just two cases. The Pro38 1G reloads are all G impulse, so that's all you lose (the 2G's are all H impulse) and you gain the extra 9 6GXL (all J impulse) motors without having to buy a third case. It does make all of the reloads other than 4G and 6GXL a bit heavier since there is a bigger case and extra spacers you have to fly (i.e. in the normal starter set a 6G motor flies stock, in this set you use the 6GXL with an XL spacer and a standard spacer), the 4G's (all I impulse) win since you're flying them in the right case rather than a 6G with 2 spacers. It just seems like a better overall deal to me especially if you want any of those 6GXL J motors.

I think they have a pretty good price on buying the full set of cases and not having to deal with any spacers also, if you choose to go that route.
 
Last edited:
bobkrech said:
Go to the motor guide at thrustcurve.org and type in your rocket diameter, dry weight, motor diameter, and maximum casing length, specify CTI, and run the guide for all motors. Download the CSV file with the results. If the rocket has a 54 mm motor mount, add the extra weight od a 54/38 adapter and repeat for 38 mm motors

Now you have the results you seek.

Bob
Click to expand...

Cool! I have to admit I thought thrust curve was just a repository for test data, I didn't realize it had sim capability!
 
SP_2870_model_EMD_GP9_locomotive_picture-1024x651.jpg


Ops! Wrong Hobby.
 
grouch said:
Take your pick. I have seen both happen a couple times a piece.
Click to expand...

Saw it enough I just sold my pro38 gear to pickup Loki. Which has the benefit of no hazmat for most 38 H/I loads. I know this isn't supposed to be a bash thread, but the 38 design is so bad CTI dumped it in the other case sizes and used closures.

my advice, remove the nozzle, seat the liner with a spacer, and CAREFULLY thread it in last, and once.
 
DizWolf said:
Saw it enough I just sold my pro38 gear to pickup Loki. Which has the benefit of no hazmat for most 38 H/I loads. I know this isn't supposed to be a bash thread, but the 38 design is so bad CTI dumped it in the other case sizes and used closures.

my advice, remove the nozzle, seat the liner with a spacer, and CAREFULLY thread it in last, and once.
Click to expand...

I really wish CTI would re design the closure system for 38 and replace it with a normal closure like the rest of the line. I usually pop the nozzle off and thread it in separately like you said, and I like to build reloads the day before the launch so I don't rush and forget something (like the case :)) at the launch.
 
I believe that's been discussed before, perhaps not by CTI but others with the same wish.

The issue is it would require recerting every load and new cases. Which is a semi huge hurdle.
 
DizWolf said:
I believe that's been discussed before, perhaps not by CTI but others with the same wish.

The issue is it would require recerting every load and new cases. Which is a semi huge hurdle.
Click to expand...

Don't forget the thousands of cases out there that would become obsolete....unless re-loads were continued to be made for both & that would defeat the purpose.

If one takes the time to learn how to use these properly, there are no more issues than any other stuff out there being used.
A tiny bit of grease rubbed on liner will make it slide in easier.
Never force the re-load in by nozzle. Push load in first, if there is too much resistance use a spacer to seat the re-load.
Screw in nozzle carefully, Do not cross thread.

If any problems ASK some one to help. No point in risking a rocket.

There will always be instances of bad liners,casting tubes etc. all manufacturers go through that from time to time. They are at the mercy of their suppliers.
 

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