i know this had been done...but have i lost it?

[shaunjohnson]

hey guys! long time no type
i came up with the idea myself but after a brief search i found similar projects throughout the forum.
the main difference is that, 1. i has bigger motor (cheaper qual) and 2. only rwd.





after Sundays race meet and blowing both revo diffs on my 2200kv setup i was sick of getting too much power sent to the front wheels no matter what i did so to save weight and cost i was gonna put in a solid centre.

then i looked at my 1/4th scale airboat over in the corner and hatched an evil plan.

pretty straight forward, motor bolted to skidplate/mount thing and revo Uni-joint on the motor end of the prop shaft. the diff end of the prop shaft has a summit CVD.

the ratio's according to mikes calculator show up good. 249kv motor, revo diff (13/37?) = about 41mph on 6s lipo which is exactly what i was geared for before the conversion.

so far my main problem is setting up the MMM and getting the motor to start nicely. the other issue is weak diffs so ive built a brand new revo diff to run in the mean time till i can get my hands on an LST diff and case.
still have to make a skid plate to protect the front of the motor.

other than that....anyone have any tips and tricks they might relinquish?

thanks guys,
shaun

[nitrostarter]

Are you sticking with 2wd? Or you going to use a thru-shaft outrunner to use 4wd?

[shaunjohnson]

just edited the post for the pics...didnt show up first time.
umm no i'll be sticking with 2wd for the time being.
i was growing sick of sending too much power to the front wheels and with a tight little track like we have 2wd might actually help in the corners
looks like it wont be very hard to go 4x4 though but i'll need an extra bearing i reckon (and the shaft will need a little modding.)

[mckrill]

I love the idea, but my self never found the proper tempting parts to start the project. Did you run it yet (motor looks clean..) If so - How's it running?

Curious!

[_paralyzed_]

The biggest problem I''ve read about using outrunners is poor start up. You can try to increase timing and punch, in the end the answer is lower gearing. (lower gearing, more voltage, lower kv motor, etc. etc.)

[suicideneil]

The MMM does have settings for outrunners/ multiple-pole motors, have a look at those, and try raising the start power & timing, that usually helps. Otherwise, Linc & Sike are the outrunner gurus to consult...

[lincpimp]

Since I did this a while back (temp forum days...) I will throw in my 2 pennies.

Start power all the way up. You NEED good batteries, short wires, the biggest bullet connectors you can find or direct solder the motor wires to the esc. Play with the timing, as that will help. I ran with fully disabled punch control. That seemed to help startup.

Now the big fix, run some negative exponential on your throttle channel. This wa the final cure that got my outrunner projects really working well. Having a really good motor is also a requirement. I tired some cheapo outrunners and eneded up with axi motors. inda like running a feigao vs a neu. Both get the job done, but the feigo runs hot. Likewise the cheaper outrunners will not startup as well, or be as smooth. Axi motors are not very expensive, and can be found used on rcgroups. I have run the tiny 2217 on my 1.9 scale crawlers and had excellent results, and have run the 53series mktos like the on in the pics you have too. Scorpion makes good motors too, so I have heard.

[shaunjohnson]

thanks for the help guys

did a little tweeking, start power mid, timing normal.
improvment in startup, start power needs increasing more, possibly timing too.

all in all, it's great. a little slow but that dosent matter because race speed isnt that fast anyway and it's ridiculously quiet!!

temps were great too, pretty good for a $60 motor i'd say. man i'd love to try an AXI one day

[mckrill]

Possibility for a video?

[shaunjohnson]

Originally Posted by mckrill

Possibility for a video?

"coming soon to a website near you"

[shaunjohnson]

timing highest (20)
start power high
punch control @ 25%

can you hear it? it seems to have some high speed "cogging" or a lagg, a whRRRR noise or something under hard acceleration?
any ideas on the cause? i thought it might have been timing issue but now i think it might actually be lipo related

[mckrill]

Hmm, what LIpos do you have? I didn't find that information in the thread.
It seem to run quite well anyhow, perhaps the problem is gone on a less grippy surface?

[shaunjohnson]

dont bash me...it is a turnigy 30-40c 6s 5000mah
i ran these lipo's because my previous setup was low draw.
with throttle moderation the problem goes away.
lipo's arnt overly warm...well...at all, and ESC fan isnt on, niether is the motor very hot (even on the windings, after 1 full pack they only hit 30*c)

[What's_nitro?]

It's just electrical noise from the motor, so it's not your diff about to explode or anything.

In my experience this is pretty normal. Outrunners make lots more noise than inrunners; I think because there is more EMF turbulence inside them. When you put more load on it (accelerate) the fields get stronger and so does the noise.

Though if it feels laggy, maybe try 20% PC? As long as the batteries are still "good" I don't think they are the problem.

[shaunjohnson]

the noise isnt continuous though.
when the motor has started and then you punch it you get the noise heard at 20 seconds and 27 seconds. a real RRRRRRR noise accompanied by a lack of power. whereas the rest of the passes are relatively silent.