Electric Open B is reality in 2007 Q&A

Post by **boiler** » Thu Nov 15, 2007 10:15 am

If waiting for Spring, you might try visiting the "Toledo Show" about the first week of April. You usually find a lot of stuff that is new. The RCCA booth has been across the isle from Wildcat fuel for several years and that brings us a lot of traffic. Last year we had electric booths outnumbering nito booths.

drewjet · Post by **drewjet** » Thu Nov 15, 2007 1:55 pm

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by BenJammin
 I did have my eye on the Scorpion 30-14's. Are you rolling your own Drew?

Electric combat is so darn nice I just hate to have to go back to slimers.
<hr height="1" noshade id="quote"></blockquote id="quote">

I roll my own to get a KV that matchs my desired RPM and battery requirements.

Lee Liddle · Post by **Lee Liddle** » Wed Nov 21, 2007 8:21 pm

Here`s a pic of a couple of Ammo motors, I think you can read the numbers.
The larger one (36-50-1500kv) is suitable for Open B. It has 100 more kv than the motor that I ran this year, and weighs 1/4oz more (about 8.5oz) I just ran it on an 8/4 APC clone on my cheap ($80) 5s2p 4500mah lipos and got a little over 20k at 50a. These numbers are almost identical to what I`ve been getting all year on the Quannum Drive motor from Hong Kong.

The really good news is that although Tower Hobbies lists a non-sale price of about $70. They must not be selling, because they have them on their web site for $35 each.

If you want to give Open B electric a try, I`d recommend this motor. I plan on buying several more at that price.

Add a $35 esc and an $80 battery, and you have a good powerful set-up at a pretty reasonable price.

BenJammin · Post by **BenJammin** » Wed Nov 21, 2007 9:13 pm

Thanks for the heads up Lee. I just might have to give one of those a try!

What prop adapter are you using?

Lee Liddle · Post by **Lee Liddle** » Wed Nov 21, 2007 10:12 pm

The prop looks to be a copy of the APC 8/4 sport prop. I bought it from United Hobbies (now Hobby City). I think it was $1.50, maybe less. It`s well made, and looks to be nylon with some kind of reinf fibers inside, like the APC.

They were out of stock the last time I checked, but I`ll buy more when they are available. This is the prop that I ran at my last contest in Houston, ad I was very happy with the performance. They are very smooth, have no sharp edges, and don`t need ballancing.

The prop adapters shown were bought from Hi Models in China for about $3.50 each. They have a steel shaft which really grips the motor shaft once you tighten it. It stays put when you need to change props, but can be removed with some tapping when needed.
http://www.himodel.com/electric/Aluminu ... _M7.8.html

For the price, I don`t see how you could beat it. I`ve had very good luck with the in runners that I used this year. Didn`t damage any in B, but did loose a couple in SSC due to midairs.

Pathous · Post by **Pathous** » Mon Nov 26, 2007 10:20 am

Lee that 36-50-1500 is rated at 35amp. Yet you are saying you are pulling 50 amps on your set up. Will this motor be able to survive more than a few runs with that much power?

Lee Liddle · Post by **Lee Liddle** » Mon Nov 26, 2007 6:38 pm

From my experience with other similar motors like the HiMax 3630-1500, it should hold up fine. I do use a HiMax heatsink $6, which helps dissipate the heat from the windings. I`ve done extended bench runs with no excessive heat, funny smells or magic smoke.

I`ll be running it tomorrow in some simulated combat heat runs (5min+ at 50a). I`ll let you know how it does.

Lee Liddle · Post by **Lee Liddle** » Mon Nov 26, 2007 6:40 pm

I`ve found that if you want to run Es with the big boys, you have to abuse everything a little. [}:)]

Lee Liddle · Post by **Lee Liddle** » Wed Nov 28, 2007 8:01 am

I ran this motor several times yesterday at 18.5v and 45a, and it looks good. There was some heating of course, but nothing too bad. Using the HiMax heatsink seems to keep the motor happy.
Good rpms on an 8/4 prop MA or APC. It might pull a 9/4 on less V and more A, but then you`d be going way over the suggested A limit. An 8/4 seems to be all the prop that motors of this size can handle at high rpm.

Lee Liddle · Post by **Lee Liddle** » Tue Dec 11, 2007 2:03 pm

I ran these motors at the contest last weekend in Florida.

The temps were in the 80`s and it was fairly humid. The Ammo 36-50-1500 performed great, giving me aprox 21k at 50a 18.5v static on the 8/4. Although I was not the fastest plane, I was plenty fast enough.

I did damage one motor. I cut the tail off of Grasshoppers Avenger. The impact knocked the back cover off of the motor. This allowed the shaft to rub on the windings or perhaps short out. This either shorted out the ESC or burned it out from over amping it.

There was some smoke and a small flame as the ECS burned out. I thought that the Lipos had been hit, but it was the motor/esc. I switched out the motor/esc and competed with the plane later in the day, after a quick test flight.

Scratch a motor and esc, but that`s combat. This is the only power equipment that I lost while flying the 42 heats of Open B that I flew this year.

Pathous · Post by **Pathous** » Tue Dec 11, 2007 8:24 pm

I found some clamshell motor mounts with cooling fins that will fit the 36mm motors very well. http://www.maxxprod.com/mpi/mpi-29b.html Scroll down to the bottom of the page. This page also has the himax heatsink that Lee is using.

Lee Liddle · Post by **Lee Liddle** » Tue Dec 11, 2007 8:51 pm

Yep, those work well for adapting a motor like this to a "rail" type fuse like the Battle Axe uses.

Alex Treneff · Post by **Alex Treneff** » Tue Dec 11, 2007 8:54 pm

Lee,

One thing I've never figured out is - how do you tell the pattern of the mounting holes on any of these motor mounts? None of the sites seem to list bolt-patterns for e-mount. Is it just a guessing game?

crash_out · Post by **crash_out** » Wed Dec 12, 2007 7:09 am

That's usually the way it is , Alex. Since there are no set standards, it's usually just hold it up, and try to mark them. I use the GP dead center hole thingee....

Lee Liddle · Post by **Lee Liddle** » Wed Dec 12, 2007 7:40 am

Yep, I just use the heatsink as a pattern. Hold it in place and mark it.