Engine lengths

[Justin]

I building my first bigger rocket soon, and I need to know how far in the stuffer tube to put the thrust ring. Does anyone know how long the longest 29mm motor is? I figure I'd go by that so I could use adapters for smaller motots to add versitility. Any help would be appreciated.

 

[Rocketjunkie]

The Ellis I69 is 16" long. USR made a 29 mm J180? that was 28" long, IIRC. I would at least provide for the Ellis motor as it is currently certified. Magnum has them in stock.

 

[Justin]

I should have clarified. Its gonna be a pre-cert bird mostly, possibly used for level one cert. at LDRS on an H. That 16" motor would be most of my stuffer!

 

[ggoldy]

Justin, Mobile as in Alabama?
My longest 29mm is about 12.75".
I've stopped using internal thrust blocks. Much happer with external and positive retention.
Gary

 

[Justin]

Gary-
Naw, mobile as in traveling. My job has me all over the place..

The rocket is going to be a converted estes v2. 12" is still too long I think. I have a lot to learn. Okay. Don't laugh guys. What is "external and positive retention"? Other than better than thrust rings.
Thanks- justin

 

[n3tjm]

Thrust rings are part of the motor tube and go inside the motor tube... the problem is they are fixed in one location... you use a shorter motor, and you have a problem... you use a longer motor, you may have a problem.

External Thrust Rings are on the motor, usually reloadables. They prevent the motor from shooting up the rocket. Positive Retention is used to prevent the motor from ejecting backwards out of the rocket.

 

[Justin]

Ahhh. I get it it. thanks..

Do the smaller f, g, and h single use guys have external thrust rings? I planned to use single use at first, then get casings when I had cash. Not sure what to do about this motor mount now. Any suggestions guys?

 

[thomasrau]

No, the single use motors do not have thrust rings. But, you can add your own with a couple of wraps of narrow masking tape.

 

[Frodo2801]

A couple wraps of masking tape is your external thrust rings.

 

[Austin]

Justin,

All Reloadable motors hvae a thrust ring that rides against the bottom of the motor mount tube. Positive motor retention usually includes and after market retainer or homemade one of some sort. For you V2, since the base is small, I would suggest either homemade or this <a href="https://www.giantleaprocketry.com/products_retention.asp">Retainer</a> from Giant Leap...very low profile and inexpensive at $18.95 compared to other after market retainers.

Carl

 

[Justin]

thanks guys-
Carl- That slimline looks cool too. Do you reccomend the threaded one or the clip one. The threaded one is more cash, but I bet it's stronger.

I was thinking of doing the v2 in 38mm (even though I'm not even level 1 yet) so I could use 29 mm pre cert motors with an adapter , and eventually be able to put in stuff to fly with the big boys. I read the the threads on v2 mods, and the biggest I saw an estes v2 go was 29mm. With well reinforced fins (I read a thousand ways to do that, but any new ones cool) do you think the kit could handel a 38?
-Justin

 

[thomasrau]

The standard slimlines work great, most of my fleet uses them. The slimline adaptors 54/38 and 38/29 are also a great deal.

 

[Austin]

The insert Slimlines are newer and a cool concept, but I stick with the standard. The C-Clip is very strong and I can get three for the price of two others.

 

[Zippy]

One thing I found out about the Slimeline clip retainers is that the newer ones have two grooves and the older ones have only one. With either one you should position the Slimline while installing it so it fits the deeper thrust ring of the 29-180 (or longer) case. The 29/40 - 120 case has a shallower thrust ring so if you position the Slimline for that case then thats all you'll ever be able to use in that rocket. Even with a single groove older style (their still being sold) build it for the deeper thrust ring as you can always stack up washers to be able to still use it with the 29/40-120.