75 MM CTI 3 Grain or 4 Grain Motor?

Shop deals on ebay
the rocketry show
rocket sok
eggtimer rocketry
The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
4kids49

4kids49

Taz
Joined
Jul 29, 2012
Messages
1,058
Reaction score
2
Does anyone have any pros and cons for either a 3 grain or a 4 grain CTI motor hardware set? I am contemplating looking for one in holiday sales. I would like to be able to fly 2 grain 75 mm motors. Thus a 3 grain might be appropriate. With no 1 grain reloads available, a 4 grain motor with two spacers could accommodate 2 - 4 grain reloads, and could be used for a 4 grain L3 cert down the road. Any thoughts would be appreciated.
 
On more than one occasion Wildman has done a 6XL/4 combo. If you only get one (3 or 4), definitely get the 4.
 
While I have not yet flown mine, I bought a 4G set for pretty much the reason you stated. However, there is a lot of weight involved in that hardware. It would be interesting to compare the empty weight of a 4G set with two spacers with an empty 2G set. The empty 4G set with two spacers weighs 1,890 grams. Each spacer weighs 225 grams. I don't have 2G casing to weigh. These weights are for Gen2 75mm hardware BTW.
 
Last edited:
Titan II said:
On more than one occasion Wildman has done a 6XL/4 combo. If you only get one (3 or 4), definitely get the 4.
Click to expand...

Thanks.

Len B said:
While I have not yet flown mine, I bought a 4G set for pretty much the reason you stated. However, there is a lot of weight involved in that hardware. It would be interesting to compare the empty weight of a 4G set with two spacers with an empty 2G set. The empty 4G set with two spacers weighs 1,890 grams. Each spacer weighs 225 grams. I don't have 2G casing to weigh. These weights are for Gen2 75mm hardware BTW.
Click to expand...

Thanks Len. I have thought about the weight. I was thinking more about total cost. The extra weight of a 4 grain motor for a 2 grain reload wouldn't bother me much. It will take a pretty amazing deal to get me to purchase at this time. I will see what comes up. I really want to get GPS going, as well as other things to support my 54 mm stuff.
 
Last edited:
What I have found through buying casings in the past is if you buy for your current rocket say it's a 2 grain case but don't account for growth and future rockets, at least a 4 grain case with two spacers you will regret it rather quickly. The extra money you spent on that 4 grain case is nothing compared to buying a whole bigger casing down the road because you shortchanged yourself.
 
glenbo said:
What I have found through buying casings in the past is if you buy for your current rocket say it's a 2 grain case but don't account for growth and future rockets, at least a 4 grain case with two spacers you will regret it rather quickly. The extra money you spent on that 4 grain case is nothing compared to buying a whole bigger casing down the road because you shortchanged yourself.
Click to expand...

That is definitely true. It is $18.00 more for a 4 grain motor than a 3 grain motor, but $170 more for a 4 grain case if I bought the 3 grain motor.
 
Check out the black friday deals at Sunward on CTI hardware. https://www.sunward1.com/cti-pro-75-hardware
I just picked up a 75mm-5G case. Sales go thru Monday so check Wildman on Saturday morning for anything better. I would agree with the other responses and go with a larger case and use spacers if needed.
 
Len B said:
While I have not yet flown mine, I bought a 4G set for pretty much the reason you stated. However, there is a lot of weight involved in that hardware. It would be interesting to compare the empty weight of a 4G set with two spacers with an empty 2G set. The empty 4G set with two spacers weighs 1,890 grams. Each spacer weighs 225 grams. I don't have 2G casing to weigh. These weights are for Gen2 75mm hardware BTW.
Click to expand...

Well, in this case the 4G+2SP weight should be compared to 3G+1SP, not plain 2G. I also think it is worth noting that none of the 2G motors are particularly high performance, and that you get a ton more impulse bumping up a little. So in my mind the 2G motors are best for lower altitude flights, where the spacer weight penalty may even be a benefit.

I was agonizing over a similar question with 4G and 5G cases, because I like the sound of many of the 5G options like pink, imax dual, and the long L395. However I went with the 4G and could not be happier with it. Having M1830 on the high end with a K2000 on the low is simply awesome; great versatility.
 
watermelonman said:
Well, in this case the 4G+2SP weight should be compared to 3G+1SP, not plain 2G. I also think it is worth noting that none of the 2G motors are particularly high performance, and that you get a ton more impulse bumping up a little. So in my mind the 2G motors are best for lower altitude flights, where the spacer weight penalty may even be a benefit.

I was agonizing over a similar question with 4G and 5G cases, because I like the sound of many of the 5G options like pink, imax dual, and the long L395. However I went with the 4G and could not be happier with it. Having M1830 on the high end with a K2000 on the low is simply awesome; great versatility.
Click to expand...

All good stuff. Your motor budget sounds bigger than mine at the moment! lol Crazy Jim has said that the CTI 75 mm 2 grain reloads are a steal for the value. With a good motor sale, and reasonably priced reloads, I could at least fly some 75 mm stuff and get used to the equip. I wouldn't be able to fly 75 mm for awhile, but boy am I a sucker for motors. People should really check out the Sunward CTi deals. They are close to 30% off and I believe there is no tax for U.S. customers, for all of the CTi motor hardware. I am going to buy something. That's for sure.
 
It really depends on on the size of your rocket and how high you want it to fly. I bought the CTI 75mm 4 grain motor form Wildman, during L3 Labor Day Certification special.
I was told the 75mm motor will only accept 1 spacer. It was a great deal. However, with the 4 grain casing and one spacer you can fly at least 4 M's and 13 L reloads. If you need to fly higher
go with the 5 grain casing with a spacer.
 
Definitely, the 5-grain, you can use a spacer for a 4 grain reload.
Consider, if you can do research motors at your local site, I would go with a 75-6000 Loki case.
You can burn Loki reloads . You can also burn the Aerotech reloads and those are a bargain, all you need is the CTI nozzle holder and adjustable fwd closure.
Then you could burn any 75mm CTI reload, I have fitted them all and they work.
Cessaroni made his reloads almost identical to the Aeortech reloads so they would work in his hdw.
 
Spicer007 said:
It really depends on on the size of your rocket and how high you want it to fly. I bought the CTI 75mm 4 grain motor form Wildman, during L3 Labor Day Certification special.
I was told the 75mm motor will only accept 1 spacer. It was a great deal. However, with the 4 grain casing and one spacer you can fly at least 4 M's and 13 L reloads. If you need to fly higher
go with the 5 grain casing with a spacer.
Click to expand...

Thanks. I have found threads saying that people have used two spacers for Pro75. I interpret the CTI instructions as saying that two spacers are allowed:

https://www.pro38.com/pdfs/Pro75_notes_V1.8.pdf

There are some good discussions about the weight of a 4 grain motor and two spacers being heavy for a 2 grain motor. All good stuff.
 
I'd suggest looking at what you intend to fly it in and see what kind of space you have. If you've got the room for a 4 grain, go with that. If only a 3, well...

Later!

--Coop
 
4kids49 said:
All good stuff. Your motor budget sounds bigger than mine at the moment! lol Crazy Jim has said that the CTI 75 mm 2 grain reloads are a steal for the value. With a good motor sale, and reasonably priced reloads, I could at least fly some 75 mm stuff and get used to the equip. I wouldn't be able to fly 75 mm for awhile, but boy am I a sucker for motors. People should really check out the Sunward CTi deals. They are close to 30% off and I believe there is no tax for U.S. customers, for all of the CTi motor hardware. I am going to buy something. That's for sure.
Click to expand...

Hah, do not tell my wife about the budget!

I hope it did not sound like I was trying to steer you away from the 75mm2G motors. They are definitely among the best motor deals around. Grab the full reload XLS file from the top of this section, add a column that is price divided by impulse, sort, and check it out. What I meant was that the L motors are too low for high altitude shots, while with K motors you are better off with 54mm minimum diameter airframes. However performance and record seeking aside, they are awesome and a ton of fun for the money.

I totally understand being a sucker for motors. I got back into this hobby under the guise of electronics but I have hardly done any of that work. I keep flying bigger, louder, and faster motors and keep enjoying it!
 
watermelonman said:
Hah, do not tell my wife about the budget!

I hope it did not sound like I was trying to steer you away from the 75mm2G motors. They are definitely among the best motor deals around. Grab the full reload XLS file from the top of this section, add a column that is price divided by impulse, sort, and check it out. What I meant was that the L motors are too low for high altitude shots, while with K motors you are better off with 54mm minimum diameter airframes. However performance and record seeking aside, they are awesome and a ton of fun for the money.

I totally understand being a sucker for motors. I got back into this hobby under the guise of electronics but I have hardly done any of that work. I keep flying bigger, louder, and faster motors and keep enjoying it!
Click to expand...

I held off on the 75 mm. I did pick up some needed 54 mm replacement stuff (like a 6XL case and tapered closure) that I lost. I really wanted the 75 mm, but I have to finish buying all of the do dads to finish my replacement Space Cowboy, and my 3 inch Punisher. Plus I am adding the Missile Works RTx and ground support stuff. Everything all adds up, but I am excited about my purchases. I am glad that I found the Sunward site. I will think about 75 mm after I fly these two rockets and my current AP inventory.
 
I didn't. I picked up the 4g case and 2 spacers. :)

I've already got the 29mm 3 grain set and 54mm 4 and 6XL and two spacers. With the 75mm 4 grain and spacers I can span from E-M with the cases I have.

From what I've read NAR and TRA were the ones that limited the number of spacers. They were worried that someone would load up a 6 grain case with 5 spacers and then not have enough grunt to get off the pad safely.
 
ChrisAttebery said:
I didn't. I picked up the 4g case and 2 spacers. :)

I've already got the 29mm 3 grain set and 54mm 4 and 6XL and two spacers. With the 75mm 4 grain and spacers I can span from E-M with the cases I have.

From what I've read NAR and TRA were the ones that limited the number of spacers. They were worried that someone would load up a 6 grain case with 5 spacers and then not have enough grunt to get off the pad safely.
Click to expand...

Nice. 75 mm is next for me. I have 38 and 54 mm starter sets and 6XL for 38 mm and two 6XL for 54 mm. I love them. I almost picked up a 29 mm starter set, but don't really need one. The 75 mm hardware and a 4 inch Punisher were hard to resist. Maybe next year.
 

Similar threads

J
75 mm crossloads
Replies
13
Views
901
jd2cylman
jd2cylman
D
75/1280 Crossload Question
Replies
1
Views
571
Doug022984
D
dknight
For Sale Cesaroni 98 mm 6 grain case, 2 grain case, closures and spacer
Replies
2
Views
887
caelan
caelan
Ulexis
Sold New CTI Hardware (24mm, 29mm, 38mm)
Replies
10
Views
636
Ulexis
Ulexis
F
LOKI M3464 Motor and a CTI 75 mm 6XL casing.
Replies
2
Views
138
3stoogesrocketry
3stoogesrocketry

Latest posts

Back
Top