mp7.5 to brushless, of course - RC-Monster Forums

mjderstine · **mp7.5 to brushless, of course -** 11.21.2008, 05:49 PM

Hey everyone.

First i wanted to say what a great site this. Its my first post, and from reading and reading and reading all the information in here i can tell there are tons of great people in here who know what they are talking about and are willing to help.

this is just a thread to show you guys what I'm dealing with in my first ever brushless conversion with a Kyosho MP7.5 buggy. it might be the kanai version, but i am not the original owner, so im not sure.
I scored this on ebay as a roller for around $150. i have never had a 1/8th buggy before and brushless is the only way i would get into the genre. Now is my chance.
the chassis has not on scratch on the bottom, but the tires are all about bald, so i guess the guy did some donuts on his driveway, put it on a shelf and sold it to me. its practically brand new.

since these pics were taken i have started to mock up a motor mount, and also cut the servo tray to make room for the motor on the right side.

ugly body...

with the stock stuff in it...

with the chassis stripped of the nitro stuff and radio box.

pics of the mocked motor mount. (yes i know its on the wrong side)
i imagine this motor mount would work for a short time and the eventually break my diff mount because it is only mounted by where the Brake system was. i have some 1/4 inch alum to carve up with a hack saw and see what i can come up with. in the end i will probably get the mount that is made here. just wondering if the 777 motor mount fits the 7.5?

thanks for taking a look guys.

DRIFT_BUGGY · 11.21.2008, 06:55 PM

What setup are you planning on running? (motor, esc, batteries etc.)

BL_RV0 · 11.21.2008, 08:34 PM

What grade is the 1/4" alum?

magman · 11.21.2008, 08:54 PM

First, Welcome to the BEST forum on the net. I agree, a bettter diff/motor mount is in order. The torque will probably twist that mount. Any Idea of set up? Best of luck!

mjderstine · 11.22.2008, 02:53 PM

thanks for the replys everyone.

planning on using tenergy 100amp esc form hobbycity, or the Supersimple 100 amp esc from hobbycity.com http://www.hobbycity.com/hobbycity/s...imple_100A_ESC the price is the tempting thing about both of them. the super simple has 4 different braking modes, so i think it would work in a 1.8th buggy app.
my eye has been on the MMM or the quark. I suppose even a MM would work too. what do you think?

i was planning to run a 4 cell Zippy pack from hobby city, probably this one.
http://www.hobbycity.com/hobbycity/s...idProduct=6416

i am not sure what grade the aluminum is. i got two small sheets of it at a garage sale. it has QV-8 5052 H-32 on it. it cut pretty easy with the hack saw. pretty sure its not t6 or anything.

also planning on running the 9XL from hobbycity. http://www.hobbycity.com/hobbycity/s...idProduct=6678

thanks for looking guys.

mjderstine · 11:38 AM

hey guys, here are som updates on the custom work so far.

ill post the link to the album in photobucket so you can see all the pics of the chassis.

i got the mount nice and sanded with some 400g around the edges and it clears the center diff cup now. i got kinda lucky with the measurements for this mount. the base is flush with the bottom of the chassis. this has allowed me to drill fromt he bottom of the chassis into the mount. i can tap the hole and reinforce the mount with a bolt directly to the chassis. i think this will greatly improve the strength of the whole mount.

i also cut the servo tray and rounded that off to make it look nice and neat.

i also have some twinforce battery trays that will work well for my batteries.

and the link to the whole album.
http://i63.photobucket.com/albums/h1...5/DSCN2254.jpg

Shark413 · 11.27.2008, 03:34 PM

Looking good, you definitely want to attach your mount to the chassis from the bottom (as you mentioned). The thickness of your mount is also good because 5052 aluminum is a little on the soft side, but 1/4 should be fine. Nice solution to those that don't have the equipment to machine the center diff bearing hole to make a one piece motor mount. Question, any reason why you have the motor mounting screw holes offset? Just curious.

BL_RV0 · 11.27.2008, 07:24 PM

Looking good- have you considered getting some shorter screws so that they sit flush to the motor mount?

mjderstine · 11.29.2008, 10:21 PM

shark:

i only have the mounting screws drawn offset. once i get a motor i will then be able to decide if it needs to be offset.

BL RVO:

they are just not in all the way. mock up only. they sit flush when tightened all the way.

in the coming weeks i will be able to get a better idea of what type of holes to put in the aluminum to lighten it up and maybe add some cooling fins, but i dont think cooling fins would be much better than just leaving it alone. almost just a gimick to put cooling fins on a motor mount.

mjderstine · 12.03.2008, 03:15 PM

hey guys, got a quick question. i have been looking around for motors for this buggy, and have found 9xl's for a decent price. but i was wondering if that motor is suited to a 4 cell battery. or would it be better to have a 5-6 cell setup?

thanks.

mjderstine · 02.25.2009, 11:41 AM

UPDATE!

got a Mamba Max for this guy. I have been looking around on how to get the Modification done so i can run 4 cells with it. I know that i can just hook a BEC up to the esc and run a RX pack, but how do i disable the internal BEC?

and do i have to change out the caps like is noted on this site by "GriffinRU"
http://forum.rcdesign.ru/blogs/4415/blog4093.html

02.25.2009, 01:11 PM

Remove the red wire from the reciever plug.
The extra caps are not necessary but can't hurt

mjderstine · 02.25.2009, 01:40 PM

thanks a lot.

i am not planning on over gearing this thing at all. just want a nice simple setup for 4 cells, and a decent motor. i dont plan to over push the esc at all.

is stock pinion 14t?
and would a good motor be around 2200kv for a buggy?

thanks

mjderstine · 03.26.2009, 09:59 AM

hey guys, i am gonna get the medusa 36-70-2300 kv for this buggy today from this site with the HW 80A esc. also gonna get the RCmonster motor mount.

any tips on what pinion i should look to get for this thing.

i am going to be running two 4800 orion packs for starters, until i can get some better SMC packs in a couple weeks when they are released.

mjderstine · 03.26.2009, 12:40 PM

i got these numbers for a 14t with the medusa 3-70-2300

what do you think?

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 14
Total Voltage: 14.8
Motor KV: 2300
Tire Diameter (inches): 4.5
Tire Ballooning (inches): 0
Motor Current Draw: 100
Motor coil Ω: 0.005
Spur/Pinion Ratio: 3.29 : 1
Total Ratio: 10.86813 : 1
Tire Circumference (inches): 14.14 inches (359.08 mm)
Total Motor Speed: 32890 RPM
Vehicle Speed: 40.51 mph (65.08 km/h)
Effective KV Value: 2222.3
KT constant: 0.59 oz-in/A
Motor Torque: 0.31 ft-lbs
Final Torque: 3.33 ft-lbs
Final Power: 1480 watts (2 HP)