D to E mod?

[scadaman29325]

I try to keep up with most of the post, but I don't remember anyone discussing the exact proceedure for converting a D motor mount to an E, and since I've never done either, I thought I'd ask ahead of time.

I need an E engine powered rocket for a club contest (E duration, E hieght, D or E spot landing). I'm more of a "participator" than a competetor, so I'm not looking for something complicated.

I'd like to use a D powered rocket like the CC express (2 stage), Stormcaster, Screaming mimi... that is locally available.

How do you mod a D to E engine mount, I believe that they are the same diameter, but the E is an inch longer, and if you use a D after the mod, do you need an adapter (1" piece of engine tube?) to take up the extra inch of mounting tube?

Ok, now that I've let you know my limited knowledge, can someone point me to a good thread or site?


Thanks in advance
SCADAman (Phil)

 

[sandman]

Basically...you have to go the other way!

You have to start out with an "E" motor mount, it's longer. 100mm I think...somebody check this for me.

I just use an "E" motor clip and a longer motor tube.

Then measure the difference between a "D" motor and an "E" which I think is 25mm.

Get an old spent motor casing (24mm) and cut a 25mm or whatever the difference is length. Clean out all the burnt chard stuff...resist the temptation to sniff it!!! and peal a layer of paper of the outside so it slips into the motor mount easy. This will be your "E" to "D" spacer.

When you want to use a "D" motor slip the "spacer" you made into the motor mount first. Remove it for an "E" motor.

And Bob's your uncle!

sandman

 

[powderburner]

Sandman is correct, the difference in length is about 25mm.

An Estes E motor casing is 3.75 inches long, or 95mm. The spacer needs to be 24mm long to slip in front of an Estes D motor to fit an E-sized MMT.

You may want to think about using other E motors, because the Estes E is really only a D-and-a-half. Total impulse is LOW, compared to other E motors. I don't know what the availability is right now for Aerotech SU E motors, but there are (were) some pretty good ones. This may require a different diameter MMT tube.

 

[Justy]

When you buy an Estes motor mount pack, it comes with two long E-motor clips, and the spacer required to use D-motors in it.

The CC Express sustainer doesn't have a motor clip, so you could just ram an E motor in there and let the extra length hang out the bottom. Check stability before flying, of course...

 

[Fore Check]

It's quite simple.

The E engine is 1" longer than the D. So, you need a motor tube that is 1" longer (3.75" long instead of 2.75") and the same diameter (24mm, or a BT50.) If your rocket already has an extended motor tube (or "stuffer tube") simply push the thrust ring 1" further in.

You put your thrust ring all the way up in the forward end like normal (when building a minimum 3.75" long mount.) You space your centering rings on the motor tube relative to either end of it like normal. If you want to use a motor hook for retention, you'll need an E length hook. Install it normally (with the insert tab up against the thrust ring and the thumb hook hanging about 1/4" off the back end of the motor tube.)

Then install in your airframe! Make sure the thrust end of the motor tube is in the same relative location as the plans call for (very close to or equal to the aft end of the airframe in most cases.)

Now, you can still fly this thing on D's, just use the 1" spacer that has been described above. You can cut about an inch off the top of a spent D or E engine and this works well. Or, you could buy an estes D/E engine mount kit, and it comes with a couple.

Just make sure that whatever you use for a spacer can be removed rather easily. I suggest that if you hack up a spent motor casing, take the time to sand it down or peel off a layer of paper so that it feels "loose" in your motor tube so you can remove it easily when you do want to put an E in there.