Saturday, January 30, 2010

Thoughts on my 24/60 motor

The 24/60 motor is really nice. The walls of the case are about twice as thick as the 24/40 case, and it just feels solider. It's built much more like the 29/40-120 casing and 29mm high-power casings than it is the 24/40 casing, in fact.

The forward closures seem similar, and to an extent they are. The main recess is the same size, and the they use the same o-ring and delay elements. However, the 24/60 closure has more threads for screwing into the case, and the threads are thicker and more separated, indicating that the new case can take a lot more pressure, which it certainly will since the closures will likely be the same for the 24/120 system.

The aft closure is also designed for higher pressure. There's also the stronger threads, and the closure itself is far bigger, with the thick flare of the larger reload cases.

The reloads are almost identical; all the parts are the the same size and positioning (except for the lengthened fuel grain) except for the aft o-ring. In the older and smaller (24/40) reloads, the aft rubber o-ring is larger in diameter (3/32" versus 1/16") than the forward ring. However, in the new, larger (24/60) loads, both rings are 1/16". The lack of size difference means one less possibility for a mistake when loading the motor, and that's a mistake that's easy to make, not easily noticed afterwards, and completely capable of causing a CATO that costs you a 40-dollar motor case.

The F35-8W kits also have a fourth o-ring, different from the 3 rings (aft, forward, and delay) normally in the kit. This made no sense, until Dick Stafford pointed me towards this assembly drawing of the F35-8. The required length of the delay element to generate an 8-second delay is just shorter than the length of the surrounding insulator tube - too short to use a cardboard spacer. Instead, they use a 1/16" o-ring as the spacer, which makes perfect sense, but only in retrospect. That the spacer is sometimes an o-ring is not mentioned at all in the instructions.

Speaking of which, they really ought to update the instructions. The halftone black-and-white illustrations are hard to understand. They should just use the colorized and modernized versions available on their website.

I love my 24/40 case, because it's so easy to use and I can use it with a variety of cheap reloads. The 24/60 case looks to be just a user-friendly and the relaods are very reasonable priced for their impulse. Currently there's only the F35W (White Lightning) reload available, but apparently there will be Blue Thunder (T), Black Jack (J) or Black Max (FJ), and Redline (R) propellants available pretty soon. I'm not a big fan of Blue Thunder because it doesn't produce much visible tracking smoke, but the smoky Black load sounds like a lot of fun, and of course I love Redlines.

I also can't wait for the 24/120 case, which will use the same closures.


KenKzak said...

Sounds good!

So now the 24/60 case ID matches the nozzle diameter instead of the nozzle fitting inside the liner tube as in the 24/40?

3 more cases and that Viper IV will really move.

The EGE said...

No; unlike the larger loads, the 24mm motors have the o-ring between the nozzle and closure instead of the nozzle and liner. Not sure why.

hmm... 4 24/60 cases = 4x 55F35 = 220H140. That's a mid-sized H motor, and I don't think the Viper IV is built to take that. The fins are not TTW.

KenKzak said...

Can you give me an accurate ID measure on the 24/60 case?

The Viper IV fins should be well bedded between the motor tubes with epoxy. It'll handle that fine.

When the kit was introduced there were some pretty spanky SU 24's available.

Actually I would be more inclined to launch it on 2 F's then airstart a pair of D12-xP's. More so when other flavors of reload are available.