Good way to mod 18mm rocket for 24mm engine?

[Steve]

Specifically - I am working on Estes' USS Enterprise, and I suspect 18mm engines will not provide enough power for decent performance. It uses a short section of BT-20 for the mmt, to which a coupler is glued, then that slips into the 'stability probe' (a longer BT-20) which fits into a groove on the underside of the saucer section. I could make a mmt using a bigger diameter tube - but what's a good way to join that to the longer BT-20? Does that make any sense? Am I right to assume this model needs more power?

Any thoughts would be welcome.

S..

 

[Fore Check]

I've not built that model, but I'd just use a centering ring arrangement to couple your BT50 motor mount to your BT20 "stability probe."

You know, make the motor tube a couple of inches longer than it needs to be. Then, put a couple of CR2050's on the end of your stability tube. Insert the end of the stability tube (with rings attached) into the forward end of the engine mount. The CR attached right on the end of the stability tube will also act as the thrust ring for the motor mount.

 

[adrian]

Is the Enterprise strong enough to withstand a D power flight? How are the warp nacelles and pylons attached, for example?

Assuming the Enterprise can survive the extra power, you're putting a heavier motor in the tail end of the model. You might want to put some extra mass at the nose end to balance, otherwise it may be unstable. I'd complete the model without the motor mount attached, put a C6-3 in the rear end of the BT-20, and find the CG. Then fit the motor mount, put in a D12-3, and add enough nose weight to return the CG to where it was with the C6-3.

(I haven't actually built this kit so I don't know if this exact procedure will work, but the basic idea is valid. Find the CG with the recommended motor, then add nose weight to put the CG there when the D12 is fitted.)

 

[Steve]

Originally posted by adrian
Is the Enterprise strong enough to withstand a D power flight? How are the warp nacelles and pylons attached, for example?

Good point. The pylons are doubled-up plywood, glued through-the-walls with some internal bracing. I'm surprised at how sturdy it seems so far. (Strong enough for a D - I don't know).

I'd complete the model without the motor mount attached, put a C6-3 in the rear end of the BT-20, and find the CG. Then fit the motor mount, put in a D12-3, and add enough nose weight to return the CG to where it was with the C6-3.

It's looking like I'll have to build it stock, then rig up some kind of 24-18mm adapter if I want to use bigger engines. The longer BT-20 has to maintain its' outside diameter in order to still fit in the groove in the saucer - so your way might be pretty close.

I haven't actually built this kit...

Yeah - you're not alone

Thanks, y'all

S..

 

[JStarStar]

Maybe you better call this guy...