Anyone ever convert an Estes Interceptor from 18mm to 24mm engines?

I'm currently building an Estes Interceptor model, and it occurred to me that it would be neat to put in a 24mm to Bt-55 engine mount and use it with D engines. I haven't found any mention of this online, and since I don't have a Rocksim file for the Interceptor to simulate the swapover, I wanted to ask if anyone has tried this?

Shouldn't be hard to make your own interceptor sim and experiment with the different motors

I'm sure someone has done this, but I've always been satisfied with my stock Interceptor, I've flown it on Aerotech D10s (but I guess those are being discontinued) and the Quest D16 is now an option.

I have done it...works nice....just get a 24mm to BT55 motor mount. You WILL need to add nose weight...I can't remember how much I used...if you dont... it will cartwheel. Add nose weight add it will scoot along nicely!
Andrew

Oh... I also went with a 3/16 launch lug when I converted it.....just to make sure it leaves the rod straight.
Andrew

The 18 to 24 mm upgrade is a great option! Add nose weight. You can still fly w 18 mm engines w an adapter.

Cool.

I will try to add some nose weight and see how the string test goes, before gluing in the 24mm/BT55 mount.

At least it appears to be workable.

I considered going from 18 to 24 on a couple of my heavy rockets, but chose to go with the AT and Quest 18mm D engines. No regrets.

Reviving an old post. I lost my Interceptor to an Quest D16, which frequently causes the rocket to veer sharply one way or another totally randomly. I had numerous perfect flights on a C5-3, but I wanted more altitude than what a C5-3 could deliver. For some reason my Interceptor hated fast burn motors (D16, D20), flying erratically.

So I have a replacement kit, that I plan to upgrade to 24mm. Curiously Rocksim says that I don't need to add noseweight. I find that suspect, and I'm going to weight the parts right out of the bag so I have a more accurate idea of what to expect. I expect to have to add noseweight though.

Bill S said:

Reviving an old post. I lost my Interceptor to an Quest D16, which frequently causes the rocket to veer sharply one way or another totally randomly. I had numerous perfect flights on a C5-3, but I wanted more altitude than what a C5-3 could deliver. For some reason my Interceptor hated fast burn motors (D16, D20), flying erratically.

So I have a replacement kit, that I plan to upgrade to 24mm. Curiously Rocksim says that I don't need to add noseweight. I find that suspect, and I'm going to weight the parts right out of the bag so I have a more accurate idea of what to expect. I expect to have to add noseweight though.

Click to expand...

See my earlier post #4.
If you did the high thrust D motors off an 1/8th inch rod this would be problematic with that kind of a rocket. Lots of bending-wiggle and possible whip. Also this kit tends to wiggle and spin a bit on higher thrust motors. Even my E version did.

"Softer" D motors like the D12 or RMS E11 are great for this rocket. Mine did great on the D12 but with the E18 it was screwy-looney. Don't forget the nose weight. I will try and find my notes as to how much I added.

Also check out the YORF forum for a post my late friend, Bruce Levison did. He posted a RocSim file of this kit with a 24mm mount and with a D12. It does do well on D motors but don't forget to put a 3/16th lug or micro-buttons on it. A 1/8th rod is NOT good for these modifications.

Andrew

Thanks, I'll remember to use a 3/16" launch lug, particularly since that way I have access to a 4' rod, not just 3'.

Yes. After building and flying mine on the C6-3 motors and not caring for the altitude or the wobbling getting off the pad on C motor power I tried the Aerotech D21 and found that it really didn't like the hard hit from the composites. Not sure exactly why it was unhappy but it never flew well and would make sharp turns mid flight. I'm thinking the fins might have been flexing but I don't know that for sure.

I finally decided to bite the bullet and pull the motor mount and replace it with a simple thrust ring. Took a lot to get the old mount of of there and get the walls cleaned up enough for the D to fit but it was worth it. As for nose weight. Yes you absolutely need to add nose weight. At least I did. First flight was on a C11-3 and the flight was low but somewhat unstable.

Looking at my logs for that day I recorded, "C11-3, winds calm, flight unstable after liftoff. Need nose weight". Afterwards I added .50 of nose weight and flew it again on a D12-3. Notes from that flight read, " D12-3, winds calm, dead straight, stable flight. Quick recovery on an 12" chute". Long story short I added .50 of nose weight to it to make it happy.

The difference in weight between an Estes 18mm C motor and the “shorty” 24mm C/D motors is roughly 15-20 grams so half an ounce (14.2 g) should work fine without making it too heavy for adapted 18mm C motors.

Coincidentally I have an Interceptor kit from the box of Bruce’s kits that were given away at one of our club launches after he passed shortly after I joined (that goofy Estes Rock-It with the carved stone look nose cone that I fly most launches was one of his too) - I think in his honor it’ll be 24mm powered when it gets built this winter.

I’ve had less than optimal flights on QJet Ds - I think there are some designs that simply don’t work well with the higher acceleration from those motors though Andrew is most likely right that rod whip is a factor. Mini buttons would look good on an Interceptor.