Bungie Launcher

[Gabe]

I've found as fun as the fun jets are, hand launching is stressful even with the lighter ones. For some reason they are prone to torque roll at slower speeds. Also, they seem to have a habit of yawing too much on the launch as well.

The next one I buy will be a bungie launch only.

[Moparmyway]

Did you Dudes add some string to the bungee as a leader ??

In the event of the steak pulling out, or the bungee breaking, the string will allow the bungees' stored energy to dissipate, and give you time to get out to the side so any projectile heading your way will miss you.

I added 50' of string to my 25' of bungee, its less to think about when getting a speedy ready for flight.

[Gabe]

How does that work? I have the pink string that came with it. Details please sir.

[akent]

Yep yep!

Details please!

I have had two occurances where I think the pink string was too taught and pulled up and smacked the plane on launch. That surely was me having the line too tight, but I like a STRONG launch!
Maybe that's not necessary....
Kent

[Moparmyway]

I threw out the pink line and just used some mason string (white nylon). I permanently looped about 100' (to make a 50' leader) and tied that to the bungee. I hook my string on the wingtip skid (used as a hook) and just walk back 40 paces (its about 10 paces of bungee, they suggest 400% stretch for max pull), raise the plane above my head and let go. With flaps enabled through DX7, I watch as the plane clears the bungee string, then I wait to see the string fall, then throttle up and flip the flaps off for flying.

In this video, you can see the string as she sits on the ground, both string and bungee are taught, no slack. By the time you get to 40 paces, you need all fingers to hold on, and you are leaning back due to the leverage the bungee has. (Gabe, you only need 1 hand, everyone else needs 2 ;D ).

www.youtube.com/watch?v=BkTVQ3caa1k

[Moparmyway]

akent,
I just noticed on your 450, you have a HK2221-08.
Are you sure of this, it isnt a 2221-06 ??

If it is an -08, what gearing and headspeed are you running ??

I have an 08 sitting around and I would LOVE to use it in one of my 450 Pros

[akent]

That's one fast Stryker, Mopar!!!

Gabe and I are using the bungee system that has the PVC launcher. The tubing that comes with it is fairly short. It gets tight in a hurry!

I think I'll try putting a long string on it, though. I think that might be the ticket for these. I'll try that this weekend.
====
I am running the Scorpion 2221-8 on my 450. That's not a typo. I am running that with a 13t pinion and turning about 3400rpm headspeed at 100% with a fresh battery. It has tons of power! It comes down cool, too.

Kent

[Moparmyway]

That Stryker has gone well past 185 mph.

Thanks for the gear and HS on the 450. I will go order a 13 tooth today !!

Now I can FINALLY put that motor to use !!

[akent]

Past 185! That's NICE! I love it!
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I had a second 450 that I built with a 2221-6 and a 12t pinion that I sold a few months ago.
The -8 has more power in my opinion.

I think you are going to love the -8! Please post when you get her going.

Scorpion does rate the -6 as being able to handle more power, but I ask you, how can you rate a motor for more power if it has:
1. The same size everything as the next motor with less power.
2. The exact same magnet arrangement as the next motor with less power.
3. The exact same number of poles as the motor with less power.
4. MORE winding turns with exactly the same litz wire which = more resistance which = higher KV than the motor with less power.

This makes no sense to me.

Kent

[Moparmyway]

The -6 has less resistance due to less winds (6 turn delta vs 8 turn delta on the -8), so it will handle a higher amp load due to less length of wire run around the stator, not necessarily better due to its higher kv.

Also, I looked again, I have the -6 motor, its 4400kv, and I do have a 12 tooth pinion for it, but I was calculating and I think an 11 tooth might proove to be equal to the -8 on a 13 tooth.

I guess I will just have to try it out sometime soon.

[akent]

Oops, I read the motor specs way wrong! Teach me to glance through.
It makes perfect sense that the -n is the winding number, that the -6 obviously has less windings, able to handle higher power.
Ugh. Sorry.
Kent