|Nov 28, 2009, 07:23 PM|
For real, I'm glad you got to get some Stryker-ing in, Kid. Also VERY glad nothing came out seriously injured. It's nice that the stock mount gives a sort of shear point that's easy to fix, rather than trashing super valuable stuff, like your Neu.
|Nov 28, 2009, 07:34 PM|
Got three flights on the new setup over the past couple days, and it flew like a rocket!
Medusa 28-40-1700kv v2
APC 7x7 prop
Turnigy Plush 80 ESC
Zippy 4s 2650 30C Lipos
The good thing was I had 3 great High Powered (For Me) flights.
The Bad thing is, the shaft on the Medusa is tweaked pretty bad, which is really upsetting considering I made 3 smooth landings. The only thing I can think of that would have caused it is if the prop caught the ground too hard on landing, but I flew an Ultrafly motor with a 2.3mm shaft and a APC 6x5.5 for almost 2 years without the shaft bending so that seems strange.
I know Medusa is closed up, but do any of you guys know of a vendor that may have more Shafts?
|Nov 28, 2009, 07:46 PM|
Joined Nov 2008
Spare Parts Stryker
Have some assorted electronics and a pile of Stryker parts... Looking for some input on a motor/esc combo to bring it all together for about a 100-110 mph plane...
Prefer to keep motor and/or esc buys at under 50-60...
Had good exp with an ARC 28-37-2.5 on a wing, open to another arc or maybe a hobby king motor...?
Parts laying around...
40 amp hobbyking esc
35 amp simple esc
Dons wicked 2700 outrunner
Plenty of turnigy tg9 and hxt900 servos
Several Flightmax 2200's 20c and even a couple 4s Excite 2200's
Just not sure how to put it all together,,
|Nov 28, 2009, 08:12 PM|
Sorry to hear about the damage, Ender.
Running a 7" prop poses additional hazard for bending prop adapters/shafts, since if the prop is vertical when it touches (even on a good landing) it can put enough pressure on the shaft to bend it.
How much of a tweak are we talking about? Ten degrees or so should be pretty safely repairable by disassembling the motor, removing the rotor/shaft and truing the shaft in a drill that you know is straight.
It's not advisable to straighten the shaft while the motor's together, since it'll damage the bearings further than they already are.
If you can locate some 4x9x4 bearings, disassembly is easy. You just heat around the back cap and smack the motor straight on the tip of the shaft. It'll drive the back cap off and you can get to the guts of the motor. This will damage the rear bearing, but if the shaft's bent, chances are the bearings are damaged anyway. I've taken my Medusa apart twice this way. The cap can be reattached with red Loctite.
If your bend is more than ten degrees, it will probably require replacing the rotor assembly. I've tried very hard to get a shaft out of a Medusa rotor, and there's no budging it.
Easiest solution to replace the rotor is to get another motor just like yours while they're still out there. Then you can run that motor, and on the chance it gets damaged in a way that leaves the shaft in good shape, you can transfer the shaft to your first motor.
If that's not in the cards, a rotor may be available from another manufacturer. Neu motors are the closest I've found. Their rotor is a tiny bit smaller than the Medusa's, but should run OK. The thing I don't know is which Neu has a rotor that would match the Medusa's length. Their motor part numbers are coded differently, so I can't tell. You may be able to contact Neu and ask if they have one with the same length (I'm guessing you'll need a rotor with about 20mm long magnets.) You won't know for sure without disassembling the motor.
If you can straighten it as described above, that's best by far. If it's too bent and you want to pursue replacement, you can PM me and I'll try to share more of my rotor repair experiences with you and see if we can come up with a solution. It will take some work, so you have to decide what you're willing to put into it.
|Nov 28, 2009, 08:35 PM|
Thanks for the repair info, the tweak is not too bad when just looking at the shaft, but with a prop adapter on it the wobble is pretty severe. The bearings may be intact, as It must have gotton damaged on the last flight, and the motor has not been ran loaded since. The wobble was visible while turning it by hand, tried a second brand new prop adapter to be sure.
I think I may be better off buying an NEU motor vs trying to track down a comparable part. The bright side is the Medusa was not too expensive (Although it averaged $20 per flight!).
I need something with a similar kv, good for 4s, and preferably with a 4mm-5mm shaft, Any suggestions? I know you mentioned the similar Mega...
Edit: I have only found more motors with 3.2mm shafts;
Mega 16/25/3 1700kv,
NeuMotor 1107/6D 1,900Kv
|Nov 28, 2009, 09:49 PM|
I was thinking the 40mm long Medusas were 25mm mag motors but was unsure.... what do you think?
My TorK motors are 43 and 44mm long 97-101 grams and have 25mm long magnets
|Nov 28, 2009, 11:47 PM|
BTW, medusa V1 shafts are VERY soft. I tweaked mine today on a vertical prop landing. Lucky a soft shaft can be straightened almost as easily as it's bent!
|Nov 29, 2009, 01:16 AM|
MEGA 16_25_1.5R Combat
I got the motor Friday.
I soldered it up Saturday night and did a KV test.
Actual KV came out right where I had hoped.
Sunday will be TP 4S-5000 30C test day with CC125A ESC.
Common sense dictates that if my ESC goes to 125A that I should test the motor to 125A on 4S......MUHAHAHAHAHAHA (I hear the Dark Side calling me).
This motor has 5mm COMBAT shaft.
5mm shaft has 2.44 times the metal in its cross section. Good luck bending that. You'll deserve a standing ovation.
How many companies make 5mm shaft 480 motors? We might be able to count them together using one hand....more like one TOE.
FYI: NEU does not. They only do the 1112 and 1115 series in optional 5mm HELI and then you better ask to have the internal fan removed because a Stryker has the motor in rear vs front (direction of air flow), and then start grinding on the integral outer fins so you can put on a more effective heat sink…same head ache that Mopar had to go through and waited over 2 months.
Although MEGA uses one of the best 3.2mm shafts, as you can see I managed to break mine using a severely out of balance APC Sport 7X3 prop on 4S a month or two ago.
p.s. the motor label is wrong...it says 1.5S (advertised 3700KV) while this motor is a 1.5R (advertised 2990KV)
Since Mopar has a MICRO Ohm meter good to 5 significant figures, he should receive this motor late in the week for resistance check ……and……and…and maybe 3S testing if he want to…..LOL
|Nov 29, 2009, 01:35 AM|
Sorry to hear about your motor's bent shaft. That is a bummer.
I had been looking to get some RPM numbers from your motor on 4S.
My brother has the Medusa 1700 (new) and the MEGA 1700 (new bearing after crash), both are 3.2mm shaft.
I'll remind him to be more careful. I no longer have any 3.2mm shaft Brushless motors.
The motor in the pic above will be changed to 5mm shaft (I'll pay extra).
p.s. The rotor from their 1110 might fit your motor....that one or 1107 (ask Steve NEU).
Good luck bro,
|Nov 29, 2009, 01:50 AM|
Yeah that 5mm shaft is gonna be good to have on those expensive motors.
Hopefully your brother gets more flights on his than I did, it flew great though. My brother in law got some video of it on my camcorder, but he had a hard time following it
and gave up before the landing...
By the way, what do guys set your "Brake" on the ESC to? Do you think that brake On or Off could help prevent these types of shaft bends?
|Nov 29, 2009, 02:08 AM|
Most all of us run soft to medium brake on average speed to fast Strykers.
I've met only a hand full of people preferring no brake.
Couple of people run HARD Brake on Ultra speed Strykers.
Personally I hate to see that prop spin when I have the throttle off, which is one of the many reasons why I run brake.
I'm told that 4 pole motors have trouble stopping a prop from spinning when gliding fast. That is not an issue with 6 pole motors like MEGA as some have proven.
Of course the size of prop matters too.
To be full proof, watch the prop as you are gliding in and if it has stopped in the vertical position, bump the throttle a little and then look again to see where it stopped.
With the prop stopped 30++ degrees away from vertical, it'll be hard to break/chip a prop, motor mount , or bend a shaft.
|Nov 29, 2009, 04:23 AM|
You MUST have really hit hard to damage those bearings on your Medusa !!!
Gryphon is right about getting the NEU 1115 series to fit into a stock Stryker mount. The "H" version gives a 5mm shaft but also gives a few hours of filing to allow it to fit !!!
AND when it does fit, it is SUPER heavy that it chucks itself right out of the stock mount so easily.................well, just ask The Kid, as of now, he has thrown it out of his mount at least 2 times now.
I spoke with Bernie @ Castle a while ago, and I was having problems with 4 pole motors stopping props with higher cell counts. The instructions on Phoenix controllers tell you to NOT run full brake on cell counts higher than 3 cells, so when running 5 or 6 cells, my Medusa shafts were on suicide missions every flight. He told me that so long as you RAMP the brake, you can run 100% even on 6 cells. GREAT !!! So now I run 100% brake on everything with a medium ramp (takes 0.5 seconds to get to desired brake strength). I havent had any problems with ESC's or shafts on motors. I just align the prop horizontal before landing and the brake holds it there (if it can). On 6 cells Eagletree shows the brake uses 25-30 watts of power.........that wont harm a battery that hit LVCO (just dont glide down from 10,000 feet), or harm the ESC in any way at all. Do not worry about 30 watts overheating your motor eithor.
Gryphon is correct, the larger the prop, the harder it is to stop it and hold it in position. The heavies glide super fast, and a 4 pole motor will stop on 5 or 6 cells, but sometimes even 4 cells has a very difficult time stopping the prop before the Stryker touches ground. 6 pole motors stop WAY easier, and I havent bent a MEGA 3.2mm shaft yet. 5mm is the way to go for sure IMHO.
Biggest problems with 5mm shafts and small props (APC E series) is clearing the adapter so it doesnt bend the roots of the prop, and so the cone (nut) doesnt bottom out on the last thread and get siezed. You need some type of a spacer to move the prop away from the adapter .....................................so after a LONG search, I finally found the perfect lightweight solution !!
NORD LOCK has these tiny little lock washers in 5/16 size that just clear the adapter shaft without too much clearance. They do not hang down to throw a balanced prop out of whack, and they have teeth on every side, so your prop will get "bit" into just like a proper adapter does. Check it out..........
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|Nov 29, 2009, 08:21 AM|
If I have a motor apart and I know it's taken a hit, I replace at least the front bearing. May as well since it's already apart. The Medusa does have really tough bearings, so they may be OK.
|Nov 29, 2009, 05:26 PM|
Drove my stryker high into a tree yesterday. Poked it with three 10 foot sticks taped together today. Could not see it well from poking position. Took over an hour but it came down.
All electronics = battery, receiver, servos, ESC, motor, all still good. Battery had 3.7V per cell left. Prop ok. Wing and fins were totalled from tree impact and stick poking. All other parts were ok.
Good lesson learned: stay behind flight line.
Video is on youtube but hardly worth watching. Can see it for 2 seconds before it goes into tree. Otherwise launch and flight is never in view.
No precip last night. Now that I have the goods home safe, just looked outside, it's raining.
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