Enerjet 2250 Clone - having trouble
 

Hi,
The Enerjet 2250 was a 2.2" diameter main tube with a 3 x 29mm cluster. The 2650 was a 2.6" with 3 x 29mm cluster.
So, I got the Rocketarium 29mm Trident kit as clone material for the 2650 - it is fairly close, and the 3 motor tubes are a tight fit.
But I am having a trouble putting together a 2250 clone, mainly because it is hard to stuff 3 29mm motor tubes into anything close to a 2.2" main body tube. The next smallest Rocketarium Trident is the 24mm model, and its diameter is listed as 2.22" (BT-70 rounded up, or they may be getting this from the motor tube cluster?). For a proper 2250, I think my nearest available main body tube is a BT-70, and the original plans do call for filleting those tubes open and crushing/stuffing them in. The smallest diameter for 3 x 29mm tube cluster is 2.61", whereas the BT-70 ID is 2.175". Any other ideas?
And as an aside, what does the 2250 offer (to customers like the U.S. Air Force) that the 2650 doesn't, other than a smaller payload capacity? From the rear bumper is looks just as wide, with same motor tubes and same max diameter.
Thanks.

https://plans.rocketshoppe.com/ener...250/enj2250.pdf

I have not tried to actually pull together the parts to clone either of these, though I have thought about it several times and would like to do so eventually.

I do recall though about 12-14 years ago looking at the original plans for each and wondering very specifically about the fit of those three 29mm tubes in the 2250, just as you are questioning/asking.

As I recall, Jerry Irvine chimed in (don’t recall if it was in a thread or a PM) that, as can be seen in the 2250 plan/drawing, those three 29mm motor tubes are slit at the top which allows them to really crimp down when they are ‘shoved’ into the main bodytube. Jerry stated that the main bodytube, in response, definitely ‘triangulates’ from the distorting force of those three tubes. And that is it…just a shove fit and distorted main tube, at least on the end where the tubes are shoved in.

I personally concluded that the 2250 was, therefore, a bit of ‘rough’ design and that it was not anymore ‘sophisticated’ than that. It is no doubt part of the history of early clustered composite motor designs and is worth cloning and flying from that perspective. But, as you point out in your closing comment to your original post, the 2650 certainly does seem to be the ‘better’ vehicle and it’s design implementation is nice and clean, what with plywood bulkheads to interface the three motor tubes into the main tube.

Earl

The 2250 may have used tubing similar to the old Semroc LT-225, and of course the 2650 would be similar to LOC 2.6.
If you look at the 2250 instructions, the 29mm motor tubes have slits in them, so they can be depressed a bit to slide to allow them to press fit into the main tube.

That is correct.