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Old Jul 30, 2012, 10:11 AM
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United States, FL, Pompano Beach
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Thanks for all that great info, now I see the attraction. ESC programming will be most interesting.
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Old Aug 10, 2012, 05:04 AM
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Joined Aug 2007
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Top Fuel Engine

Yes its got 15T of .76 dia wire DLRK delta, CC25 ESC and 900 3S Battery and a


model that is 14 Ozs all up weight with battery on

Over 300 Watts with a 12x4.7 APC,

It used the battery rather fast in my garage , , I saw 27 Amps

I will try a 10x6 first off , more like 18 Amps And with the 300 Watt bursts the motor was a bit warm ,not hot , amazing
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Old Aug 13, 2012, 05:24 PM
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Joined Aug 2012
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My Dt750 sounds abit weird. I'm guessing the bearings are broken. Could anyone take a minute and listen to the sound coming from the engine?

Link:
hexTronik DT750 (0 min 50 sec)


Best regards
Daniel =)
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Old Aug 13, 2012, 08:41 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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It is almost certainly a bad bearing. That is one of the weak spots in that motor, it has rather small bearings.

If that has a 8mm bearing tube it will need two 4 x 7 x 2.5mm (MR74ZZ) bearings. If it is the later version with a 9mm tube I think the bearings are larger but I'm not sure of the size and length

I buy average quality bearings, lube them well before I install them, and replace them as often as necessary. Good idea to buy some spares too, they are usually quite cheap.

It will be worthwhile to check the size on your bearings before ordering the bearings because of the differences I mentioned above. This pose has some photos of the differences in the two variants:

http://www.rcgroups.com/forums/showp...postcount=1112

Jack
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Old Aug 14, 2012, 05:11 AM
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Thank you for your quick reply jackerbes. I'll go order some spare's right away! As I'm new to this hobby and never actually took apart these motors I wonder if I need any special tool? Abit unsecure about the "C-clip".
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Old Aug 14, 2012, 08:26 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Put the motor in a plastic bag and use a small sharp pointed screwdriver or tool to pry the clip away from the shaft. The bag will catch it so you don't have to look for it.

Then the shaft and magnet housing will slide out of the bearing races. Some pressure is required to overcome the magnets and friction in the races. Worst case you may have to press it out. Some details on doing it with typical motors here:

http://www.rcgroups.com/forums/showthread.php?t=1079423

The bearings can normally be pushed out of the bearing tube with another piece of smaller shafting or a small rod. Once you get one out the second can be pushed out with a larger dowel or rod. Here is a good thread on lubricating bearings:

http://www.rcgroups.com/forums/showthread.php?t=1665523

Your bearings are either 8mm O.D. or 9mm O.D. depending on the whether you have the early or later model. Here are some places that have bearings and clips (just 2 of many):

http://www.headsuprc.com/servlet/the...FTS/Categories
http://www.headsuprc.com/servlet/the...NGS/Categories
http://www.rcbearings.com/

eBay is a good source for bearings too, look for "bearing 9 4 2.5" and "bearing 8 4 2.5".

Jack
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Last edited by jackerbes; Aug 19, 2012 at 10:20 AM.
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Old Aug 23, 2012, 11:01 PM
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United States, CA, Rocklin
Joined Aug 2012
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So I ordered 3 of these motors for my Tricopter build, and also ordered 4 pairs of bearings... not knowing about the size difference.

http://www.hobbyking.com/hobbyking/s...dProduct=11521

Can anyone verify if these are for the old or the new motors? I have the new DT750.
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Old Aug 24, 2012, 07:24 AM
Jack
USA, ME, Ellsworth
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The old ones were 2.5mm wide but the post that describes the new ones does not mention the width, only the ID and OD. I think the is a little more length in the bearing tube at the back of the motor so maybe they went to the wider 3mm bearing too and maybe they did it on both ends.

We just need someone to fill us in on the details here...

Jack
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Old Aug 24, 2012, 04:10 PM
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maybe i will pull a bearing from my motor and compare it with the spare bearings i bought to see.
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Old Aug 24, 2012, 07:36 PM
Jack
USA, ME, Ellsworth
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That would be great info to know.

There only two variations on the motor now as far as I know and they are fairly easy to tell apart by the bearing tube diameter (9mm on the later verson, 8mm on the earlier).

Jack
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Old Aug 26, 2012, 05:28 PM
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I changed mine with these ( link of heli parts) above and they fit the HK DAT 700 and 750 they come as advertise don't forget to oil them mine were fairly dry..too late to mesure they are installed now, I am pretty sure they are 8mm OD x 4mm ID x 2.5 mm from memory but it's 100 % sure at my age :-(...
Roger
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Old Aug 28, 2012, 03:26 PM
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United States, CA, Rocklin
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Quote:
Originally Posted by subaru4wd View Post
So I ordered 3 of these motors for my Tricopter build, and also ordered 4 pairs of bearings... not knowing about the size difference.

http://www.hobbyking.com/hobbyking/s...dProduct=11521

Can anyone verify if these are for the old or the new motors? I have the new DT750.
Okay it didnt take but 2 days before one of my DT750's were in need of new bearings. So I took the bearings I ordered and compared them, and they are an exact replacement for the stock bearings So, if anyone needs bearings for their new DT750's the HK link above should work for you.

On another note; has anybody found a replacement motor mount for these motors?? Im afraid it wont take long for me to destroy one, but for $11 i guess I could just replace the motor and get a new mount along with it...
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Old Aug 28, 2012, 04:12 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Older DAT-750/DT750 identification = 8mm bearing tube at diameter where it enters the mount (hole in mount is 8mm also).

Older version bearings = two pieces 7mm O.D. x 4MM I.D. X 2.5mm wide

newer DAT-750/DT750 = 9mm bearing tube at diameter where it enters the mount (hole in mount is 9mm also).

Newer version bearings = two pieces 8mm O.D. x 4MM I.D. X unknown mm wide

We can't seem to get anyone that has one of the newer motors to lay their bearing on a rule, on edge, and tell us the width of the newer 9mm bearings...

And it would also be nice if they could also confirm that the two bearings are the same.

Lube the bearings before you use them and they will last a *lot* longer. Here is my idea of how to handle the lubrication on these bearings:

http://www.rcgroups.com/forums/showp...24&postcount=4

I have heard a number of reasons why I should not do it that way. They are all valid opinions I guess, no matter how silly some of them may sound to me (a life long motor head, ex-machinist and gunsmith, and guy who would not think of doing anything that would abuse a bearing). My way works and the bearings last longer and run quieter. But they are still small and easily damaged bearings so have spares on hand.

Any dirt found on the outside of a bearing lubricated my way will have been found on the way in, not on the way out. So it has caused no damage... That is my story and I am sticking to it!

On the motor mounting issue, throw away the headless, 1.5mm hex socket, 3mm grub screws on the motor mount and replace them with the 3mm Button Head, 2mm Socket Head screws that are seen here:

http://www.rcgroups.com/forums/showp...&postcount=997

When you put the motor in the mount, put one screw in snug it down well and use blue Loctite on it. The next day (or hours later at the minimum) put the second screw in but only take it down to a light touch against the bearing tube. Again, use blue Loctite. That will push the bearing tube into full contact against one side inside the mount and it will not wiggle or vibrate lose from pivoting on the points of two opposing screws.

If you are handy, drill and tap a second 3M-0.5 grub screw hole at 90 degrees to one of the originals. With the two holes at 90 degrees to each other you can put both grub screws in at the same time and tighten them equally tight (use blue Loctite). The bearing tube will be forces against and into full contact with one side of mount and will not vibrate or wiggle.

Jack
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Old Aug 28, 2012, 04:19 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Here is a DAT-750 on it's supplied mount attached to a E-Flite EFLM-1915 stick mount for use on a 10mm square stick on my KFoenix Stick (Slow Stick clone).

Note the 3mm Button head screw in use to lock the shaft into the magnet housing and also to hold the motor into the mount.

Jack
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Old Sep 02, 2012, 04:40 PM
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Croatia
Joined Jul 2007
117 Posts
Who manufactures DT750?

Well, I would like to make several custom rewind motors (10-12) for my quads, but what I figured out is that is pain in the a... to remove existing wiring which is either epoxied or CA in place. So I though to try to find out who make those motors and try to order 10-20 motors with empty stators. Any clue or help is appreciated

Thx.
Ivan
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