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help choosing a motor
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RUSTED
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help choosing a motor - 01.21.2009, 11:16 AM

hey,

i want a new brushless system for my maxx , but i cant decided on which kv to get , either the mmm 2200 or the 2650 , ill be only using 4s lipos , and the pinions i have are 20 and 24t and spur 62, 65, 68 , i need something that will remain cool but still go over 40 mph

and im looking for a motor for my crt.5(rcm chassis 2.2 wheels) ill be using 4s lipo with the stock spur and 18 t pinion , i want it to go over 40 mph , i was thinking of getting a medusa but dont know wat size or kv to get ????


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suicideneil
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01.21.2009, 03:51 PM

2200kv for the Emaxx, something very similar for the crt.5- I'd suggest a 50 or 60mm medusa for something in the ~7-8lb region, probably 60mm.
   
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01.21.2009, 11:55 PM

it turns out that the mmm combo is out of stock , will a mmm v3 esc with a medusa 70mm 2300 kv be a good combo ???


i also read that the mmm esc used to have manu problems did it get fixed ?? will i face any problems with the mmmv3??
   
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suicideneil
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01.22.2009, 05:30 PM

Yes, yes and no.

I would say if you only intended to ever run 4s lipo, the the 2300kv wouod be fine, but if you were thinking about 5s or 6s in future, look towards a slightly slower motor in the 1700-2000kv region.

The 1st and 2nd versions of the MMM esc had a few issues, mainly BEC related, but the V3 is proving very solid and reliable- less than a dozen known cases of escs going pop so far out of thousands sold.

You shouldnt have any issues, provided you do a good job on any soldering of connectors and programmig the radio/esc correctly.
   
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01.29.2009, 03:30 PM

i just got the Medusa 2300 kv 70m motor , and the difference between it and the feigao motors is amazijng , i dont know why was i wasting my money on feigao motors , anyways i went to the track today and stripped the rear diff , should buy another stock diff or get the hybrid bulk , i already have ofna titan diffs i think they'll fit , wat else do i need to buy?? bearing???shims???


heres a vid i made , only drove it for 5 mins at the track then the rear diff stripped

http://www.youtube.com/watch?v=eIMM3zRyZpo
   
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suicideneil
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01.29.2009, 03:49 PM

Hybrids or UE ultralites, either will do the same splendid job- hybrids would be better for you sinc you have the ofna diffs already. You will need pinions for the diffs (hotbodies sell suitable items, look up their buggy ratio diff parts), and bearings- FLM should list the size required, but I think its 5x10x5 bearings (8 in total required). Some 5x10x0.5 shims will be required also to set the mesh between ring and pinion gear.
Bad news is this means you will also need new center driveshafts or cups atleast if you run dogbones, RCM sell suitable parts in the shop.
   
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xpy
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01.29.2009, 04:05 PM

Very nice vid you made. A liitle bit dark but very well made.

Which pinion and which spur did you use in the vid? What are the temps like?
   
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01.29.2009, 04:44 PM

thanks, i was late because charging the batteries took longer than i expected that's why its dark , i am using a 20 teeth pinion and a 65 teeth spur , the temps were 115 - 130f after 10-15 mins
   
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suicideneil
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01.29.2009, 05:47 PM

I missed that vid, must be going blind...

Very well edited, good job there. I like what you've done with the FLM chassis, dont see too many modified like that, which is a shame as its a nice way to get something rather gorillamaxx-like but with better durabilty (X-braces bend sometimes) and a much better price.
   
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01.29.2009, 05:59 PM

thanx, i have found these , the bearing that come with the hb diffs are 8x16mm and i think they'll fit the hybrid bulks , im only getting for the rear since the stock rear diff stripped

i have found these

bearings
http://www3.towerhobbies.com/cgi-bin...?&I=LXJBE2&P=7


shims
http://www3.towerhobbies.com/cgi-bin...?&I=LXGPC9&P=7

will these fit???

will i need anything else???? , im already using drive cups and driveshafts instead of the stock one

this is what i have right now
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suicideneil
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01.29.2009, 06:20 PM

Nay, you have to replace both front and rear diffs, as the 1/8 scale diffs are a different ratio to stock diffs- you would have rear wheels trying to spin slower than the fronts if you only changed the rears.

8x16 bearings yeah, I remember now- funny as I wrote a tutorial on building UE diffs (old age = bad memory... 25 is old...).

The shims are the correct ones too, you should only need one or two on each pinion between the inner bearing and back of the pinion head to set the mesh.

Looks like the bearings on the diff might be the right size already as most 1/8 vehicles tend to use the same size items (9 times out of 10 anyway), but new bearings wont hurt regardless- cheap enough.

I dont believe you'll need anything else, just fill up the diffs with your favourite thickness of fluid (I use 7k and 4k, front and rear, rather generic setup) and that should be that.
   
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01.29.2009, 06:59 PM

oh ya , forgot about the different ratios , just counted the number of teeth on the ofna titan diff its 43/13 so ill have to change the pinion gear to 24t and spur to 68t to make it as with the stock diffs and i just measured the bearing and their the right size

$130 shipped for 2 hybrids
$10.28 shipped for the shims

heh, and i thought i was done upgrading this truck
   
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suicideneil
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01.29.2009, 07:03 PM

You are never truelly done upgrading, never....

$130 for the hybrids isnt too bad really- they will last pretty much forever with the ocassional service.
   
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01.29.2009, 07:12 PM

yes , it aint that bad , good thing i already have the diffs , bought an old but in really good shape ofna titan roller for 20-25$ from the lhs , i bought it to take its suspension and put it in the maxx but after reading about the titan i discovered that it had 1/8 diffs

btw does the mmm's fan operate when their is overheating or is it on all the time ??? , cause mine is never on , and how can i cover the open areas in the medusa motor , is covering it by tape ok ???


thanks
   
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01.29.2009, 07:15 PM

Quote:
Originally Posted by RUSTED View Post
btw does the mmm's fan operate when their is overheating or is it on all the time ??? , cause mine is never on , and how can i cover the open areas in the medusa motor , is covering it by tape ok ???
It comes on at 140 degrees, not sure when it turns off. You could cover it with tape if you wanted, they are there for cooling but if you are running in lots of mud and dirt it could be a good idea.


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