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Old Jul 07, 2012, 06:22 AM
Robert Roland
Guest
n/a Posts
Brushless shaft too short

I am trying to install a brushless motor into the nose of a glider
that was not originally designed for a motor. The plane's fuse is
quite narrow at the front, so it is difficult to get the motor to fit.
I already have the motor, so I'd prefer to not buy a new one.

If the motor shaft was a little longer, I could get it to work. I have
a small metal lathe, so I could easily either make new, longer shaft
for the motor out of piano wire, or I could make an extension that
clamps onto the existing shaft. Making a new shaft seems easier,
lighter and more reliable.

As an alternative to making something, are there any commercially
available methods to solve this problem?

How far can the shaft be extended before I have to add a support
bearing close to the propeller?
--
RoRo
Old Jul 07, 2012, 09:19 AM
Vance Howard
Guest
n/a Posts
Re: Brushless shaft too short

On Sat, 07 Jul 2012 13:22:21 +0200, Robert Roland wrote:


> I am trying to install a brushless motor into the nose of a glider that
> was not originally designed for a motor. The plane's fuse is quite
> narrow at the front, so it is difficult to get the motor to fit.
> I already have the motor, so I'd prefer to not buy a new one.
>
> If the motor shaft was a little longer, I could get it to work. I have a
> small metal lathe, so I could easily either make new, longer shaft for
> the motor out of piano wire, or I could make an extension that clamps
> onto the existing shaft. Making a new shaft seems easier, lighter and
> more reliable.
>
> As an alternative to making something, are there any commercially
> available methods to solve this problem?
>
> How far can the shaft be extended before I have to add a support bearing
> close to the propeller?


Music wire is often too soft to use as a motor shaft. Maybe contact the
maker of the motor and see if they have a shaft that is longer that would
work with your motor?



--
to reply via email: vhoward1122 at gmail dot com
Old Jul 07, 2012, 09:35 AM
BobH
Guest
n/a Posts
Re: Brushless shaft too short

On 7/7/2012 4:22 AM, Robert Roland wrote:

> I am trying to install a brushless motor into the nose of a glider
> that was not originally designed for a motor. The plane's fuse is
> quite narrow at the front, so it is difficult to get the motor to fit.
> I already have the motor, so I'd prefer to not buy a new one.
>
> If the motor shaft was a little longer, I could get it to work. I have
> a small metal lathe, so I could easily either make new, longer shaft
> for the motor out of piano wire, or I could make an extension that
> clamps onto the existing shaft. Making a new shaft seems easier,
> lighter and more reliable.
>
> As an alternative to making something, are there any commercially
> available methods to solve this problem?
>
> How far can the shaft be extended before I have to add a support
> bearing close to the propeller?


A creative motor mount might be a better choice than extending the
shaft. I have snapped motor shafts that were not extended, in very minor
bungled hand-launches. Extending the shaft would add leverage to make
that problem worse.

Good Luck,
BobH
Old Jul 07, 2012, 11:20 AM
Robert Roland
Guest
n/a Posts
Re: Brushless shaft too short

On Sat, 7 Jul 2012 14:19:45 +0000 (UTC), Vance Howard
<itsme@example.invalid> wrote:


>Music wire is often too soft to use as a motor shaft.


I have noticed the shafts are glass hard, but I have never been able
to figure out why they have to be so hard. I have made two shafts from
piano wire myself earlier, and they are still flying just fine.

Why are the shafts so hard?


>Maybe contact the
>maker of the motor and see if they have a shaft that is longer that would
>work with your motor?


This is a cheapo Chinese motor, so that's probably not even worth
checking.
--
RoRo
Old Jul 07, 2012, 11:22 AM
Tim Wescott
Guest
n/a Posts
Re: Brushless shaft too short

On Sat, 07 Jul 2012 13:22:21 +0200, Robert Roland wrote:


> I am trying to install a brushless motor into the nose of a glider that
> was not originally designed for a motor. The plane's fuse is quite
> narrow at the front, so it is difficult to get the motor to fit.
> I already have the motor, so I'd prefer to not buy a new one.
>
> If the motor shaft was a little longer, I could get it to work. I have a
> small metal lathe, so I could easily either make new, longer shaft for
> the motor out of piano wire, or I could make an extension that clamps
> onto the existing shaft. Making a new shaft seems easier, lighter and
> more reliable.
>
> As an alternative to making something, are there any commercially
> available methods to solve this problem?
>
> How far can the shaft be extended before I have to add a support bearing
> close to the propeller?


* Get the right size ground shaft material from McMaster-Carr or Enco or
something -- music wire is hard to machine, and not accurate.

* If you use ground shaft material you should be able to get an off-the-
shelf bearing that'll fit. Set the motor back as far as you need and
just press the bearing into a hole in a plywood bulkhead.

* Make an extended prop driver -- that should be easier than installing a
longer shaft, and if you're lucky you'll be able to bolt it to the motor
bell.

* Make that custom motor mount that was suggested (although we can't see
the nose you're putting it in, so maybe that's just not in the cards).



--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
Old Jul 07, 2012, 11:41 AM
Robert Roland
Guest
n/a Posts
Re: Brushless shaft too short

On Sat, 07 Jul 2012 07:35:04 -0700, BobH
<wanderingmetalhead.nospam.please@yahoo.com> wrote:


>A creative motor mount might be a better choice than extending the
>shaft.


The motor diameter is just about the same as the spinner, and the
fuselage is a rounded rectangle balsa construction, so I cannot see
any way to make this look even remotely decent. Getting a bigger
spinner might be an option, though, but those folding prop hubs are
not exactly cheap.


>I have snapped motor shafts that were not extended, in very minor
>bungled hand-launches.


Yes, they are incredibly brittle. I snapped two of them in one crash
into water (on a Catalina seaplane).


>Extending the shaft would add leverage to make
>that problem worse.


I understand that. I'd be willing to risk the compromise, at least as
an experiment. If it turns out I damage them too often, I'd have to
try another solution.
--
RoRo
Old Jul 07, 2012, 05:41 PM
BobH
Guest
n/a Posts
Re: Brushless shaft too short

On 7/7/2012 9:22 AM, Tim Wescott wrote:

> On Sat, 07 Jul 2012 13:22:21 +0200, Robert Roland wrote:
>

>> I am trying to install a brushless motor into the nose of a glider that
>> was not originally designed for a motor. The plane's fuse is quite
>> narrow at the front, so it is difficult to get the motor to fit.
>> I already have the motor, so I'd prefer to not buy a new one.
>>
>> If the motor shaft was a little longer, I could get it to work. I have a
>> small metal lathe, so I could easily either make new, longer shaft for
>> the motor out of piano wire, or I could make an extension that clamps
>> onto the existing shaft. Making a new shaft seems easier, lighter and
>> more reliable.
>>
>> As an alternative to making something, are there any commercially
>> available methods to solve this problem?
>>
>> How far can the shaft be extended before I have to add a support bearing
>> close to the propeller?

>
> * Get the right size ground shaft material from McMaster-Carr or Enco or
> something -- music wire is hard to machine, and not accurate.
>
> * If you use ground shaft material you should be able to get an off-the-
> shelf bearing that'll fit. Set the motor back as far as you need and
> just press the bearing into a hole in a plywood bulkhead.
>
> * Make an extended prop driver -- that should be easier than installing a
> longer shaft, and if you're lucky you'll be able to bolt it to the motor
> bell.
>
> * Make that custom motor mount that was suggested (although we can't see
> the nose you're putting it in, so maybe that's just not in the cards).


Also, make sure you have good airflow over the motor, especially if it
is set back in the fuselage.

BobH
Old Jul 07, 2012, 08:23 PM
Skywise
Guest
n/a Posts
Re: Brushless shaft too short

Robert Roland <fake@ddress.no> wrote in
news:eeogv71j9hb8rv56kjbqro4qigg093fvvr@4ax.com:


> Getting a bigger spinner might be an option, though, but
> those folding prop hubs are not exactly cheap.


Just out of curiosity, define "not exactly cheap."

I had a Multiplex Easyglider that I learned on a few years
back. When I got tired of burning up the standard brush
motors, I upgraded the system to brushless. I used the
spinner hub from a Parkzone Radian.

http://www.parkzone.com/Products/Def...ProdID=PKZ1018

Only $7.

To modify the plane, I chopped the nose off and made a bulkhead
to attach the brushless. I made sure to chop off so the overall
length remained the same (thus keep the CG pretty much the same).

Then, using spare foam, I carved up a new cowling to make it
all streamlined. Admitedly, this wasn't meant as a showpiece.
Currently, the bird is in pieces awaiting the budget to let
me fly again, so I can finish it's conversion to a twin. It's
been rebuilt so many times it's not much of a 'glider' anymore.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Sed quis custodiet ipsos Custodes?
 


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