[NSRCA-discussion] Cooling outrunners
Rex LESHER
trexlesh at msn.com
Wed Dec 20 16:38:27 AKST 2006
I am wondering how many balance the spinner assembly... I've been doing that for years, and I can tell you that I haven't found one yet
that didn't need some major grinding. I usually also index the spinner to the backplate so that every time I have it off and on, it goes back
together the same. I always do the indexing first, putting the heavy side of the spinner to the light side of the backplate. It helps by offsetting the the imbalance and eliminating a bit of grinding to get it all in balance... I don't know how important it is on a fuel motor, but I assume it could have a dramatic effect on the small bearings in the outrunners....
Rex
----- Original Message -----
From: Chad Northeast<mailto:chad at f3acanada.org>
Cc: NSRCA Mailing List<mailto:nsrca-discussion at lists.nsrca.org>
Sent: Wednesday, December 20, 2006 5:17 PM
Subject: Re: [NSRCA-discussion] Cooling outrunners
Hi Dean
The bearing life on my motors has been good, I have an old 30-10 pushing
500 flights, and my Evo is around 250-300 I would guestimate.
The bearing issues on the Pletty motors seems to me to be very related
to prop balance. I use a small aluminum 8mm bushing (the TT one for
spinners actually) that fits right in the molded part of the hub
center. APC drilled holes are often not properly centered so that helps
to ensure I am running the prop as concentric with the motor as
possible. I know guys have hurt bearings on these motors running either
the Pletty motor in the nose (In my mind that system has huge potential
for imbalance) and using APC's drilled hole without balancing the prop.
Just some of my thoughts on bearings :)
Chad
Dean Pappas wrote:
> Hi Chad,
> Yes everything gets better when you don't have to run at peak load very often.
> Hey ... that's how the best wet setups work too.
> If I can get the motor temps down without too much fuss, I always will:
> not just the magnets, but the bearings and gearboxes like it too.
> I am still waiting to see what happens long term with outrunner bearings.
>
> Why? In the CL Stunt setups, the first couple of tries with planetary gearboxes were ALL abject failures.
> Gearboxes were failing in literally a handful of flights. Stunt ships corner hard (maybe 90 degrees in 1/3 second)
> and we are currently seeing everything from ~80 flights to >300 flights before outrunner bearing problems start.
>
> Back to RC and heat.
> I block 50% of the air to the battery (one cheek inlet) with a foam rubber plug on
> days under 70 F (~20 C) and at maybe 55 F (15 C) I take a piece of tape and cover half of the remaining inlet.
> That allows me to keep my 5300s up to maybe 95 ~ 100F on cool days.
> I typically get a 40 F (20 C) rise on warm days with everything opened up.
> I am also on the throttle a bit more on hot days.
> The Extremes will be welcome in that regard.
>
> later
>
> Dean Pappas
> Sr. Design Engineer
> Kodeos Communications
> 111 Corporate Blvd.
> South Plainfield, N.J. 07080
> (908) 222-7817 phone
> (908) 222-2392 fax
> d.pappas at kodeos.com<mailto:d.pappas at kodeos.com>
>
>
> -----Original Message-----
> From: nsrca-discussion-bounces at lists.nsrca.org<mailto:nsrca-discussion-bounces at lists.nsrca.org>
> [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Chad
> Northeast
> Sent: Wednesday, December 20, 2006 12:37 AM
> To: NSRCA Mailing List
> Subject: Re: [NSRCA-discussion] Cooling outrunners
>
>
> Hi Dean
>
> Quite true about the magnets, but I have flown with my motor at 150F and
> on days where it doesnt get above 65F....I can not tell the difference
> in performance, probably because there is such excess power in these
> setups to start with.
>
> Pack temperature on the other hand is very important, OAT below 10-15C I
> have to start restricting cooling on the batteries or they dont get warm
> enough to provide good power. The new extreme packs are better about
> this than the Prolites, but still very noticeable on certain days.
>
> Chad
>
> Dean Pappas wrote:
>
>> Bob, you're a genius!
>> I suggested this to an E-powered CL Stunt buddy in the Netherlands
>> some months ago because the Stunt guys have a long history of styling
>> planes with chin scoops placed far back. These often require a 3/4"
>> long prop drive extension to place the cylinder back farther, and the
>> use of a short venturi. They cowl much easier than computer carbs!
>>
>> Hi Chad,
>> Makes you wonder what some of these guys were thinking when they
>> placed the cooling and cheek inlets. ?? **^^$$!!!
>> The inlet airbox can shroud the aft end of the motor and the sleeve
>> dump into a front exit plenumm. Now the trick is the exit from there.
>> I think that a big elbow like a turbopropo exhaust would be cool, as
>> would be cheek cowls with no entry holes just exits. The exit plenum
>> just behind the spinner would have to duct into the cheeks. Notre that
>> flying without a spinner will wreck the cooling! A row of exhaust
>> stacks like a P-51 could be boxed in and used to suck the warm air out
>> of the exit plenum. I need to draw a picture. That'll take a while,
>> especially around Christmas.
>>
>> The colder the magnets are, the stronger they are, and the less
>> resistive the copper is, so cooler is always better for the motor. The
>> same is true for the ESC: MOSFETs are less resistive the cooler they
>> are, so everything gets better in the Antarctic except battery
>> performance.
>>
>> later,
>> Dean
>>
>>
>>
>> Dean Pappas
>> Sr. Design Engineer
>> Kodeos Communications
>> 111 Corporate Blvd.
>> South Plainfield, N.J. 07080
>> (908) 222-7817 phone
>> (908) 222-2392 fax
>> d.pappas at kodeos.com<mailto:d.pappas at kodeos.com>
>>
>> -----Original Message-----
>> *From:* nsrca-discussion-bounces at lists.nsrca.org<mailto:nsrca-discussion-bounces at lists.nsrca.org>
>> [mailto:nsrca-discussion-bounces at lists.nsrca.org]*On Behalf Of
>> *Bob Richards
>> *Sent:* Tuesday, December 19, 2006 9:27 AM
>> *To:* chad at f3acanada.org<mailto:chad at f3acanada.org>; NSRCA Mailing List
>> *Subject:* Re: [NSRCA-discussion] Cooling outrunners
>>
>> Is there any reason why you can't duct the air to blow into the
>> rear of the motor, and provide a way for it to escape from the front?
>>
>> Geez, I'm just thinking that leaving the spinner off, or use a
>> really small spinner, would be the way to go.
>>
>> Bob R.
>>
>>
>> */Chad Northeast <chad at f3acanada.org>/<mailto:chad at f3acanada.org%3E/>* wrote:
>>
>> The problem with a lot of composite fuse models (Twister
>> included) is
>> that the inlets in the chin and cheeks are often right at the
>> rear or
>> even behind an outrunner.....so ducting toward them is very
>> difficult.
>> I have to agree that a proper ducting system is crucial for
>> cooling. I
>> use a very simple short radius 90 bend in a peice of depron
>> that pulls
>> air in from the chin, I see about a 20C rise in temp without
>> it, other
>> than that I dont really do anything special. The motor will
>> operate at
>> up to 170F without complaining so as long as its 20-30F below
>> that all
>> is good :)
>>
>> Chad
>>
>> ------------------------------------------------------------------------
>>
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