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  1. #1

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    GST 7.7 Brushless conversion help needed

    I was given a Cen GST 7.7 that has no motor and have been working on a brushless conversion.I am running into an ESC issue.I plan on running a KB45-XL17 700Kv brushless motor on 10s lipo's.I need a high volt ESC for this.I am trying to keep the cost down as much as I can.I was thinking on using a plane ESC but they do not have reverse.What could I do for brakes?I only have a 2 channel radio with no brake mixing.Could I use a V Tail mixer to control a servo for the mechanical brakes?Any suggestions on a esc that is affordable with reverse?Any Ideas on this would be greatly appreciated.

  2. #2

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    RE: GST 7.7 Brushless conversion help needed

    I think that is too much motor and battery. I have a converted truck with a Mamba Monster and 2200kv combo and it does a standing back flip on 4s. It is also wicked fast and at times in tight areas too fast!!

    here is a link about my build. There are some videos on there too check them out. [link]http://www.rc-monster.com/forum/showthread.php?t=22075[/link]

  3. #3

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    RE: GST 7.7 Brushless conversion help needed

    Wow that looks great.I guess 6s would be enough if that is just 4s.I saw in the thread that you burnt up a couple mamba monsters at first.Do you know why they burnt up so I can avoid burning one up myself?How is the esc holding up with time?I already purchased the 700Kv motor.Do you think I could still use it with the mamba monster esc and just use a larger pinion?Did you use the original center trans setup?I was thinking on mounting the original pinion on my motor and using the 2 speed trans that is in the truck.Think that would work?.I saw a brushless GST 7.7 on youtube running 12s with a 700kv motor so I thought I would just copy that setup.I didn't realize the mamba system would work.Sorry for all the questions.I would just like to do my conversion properly.Any other suggestions on this build would be greatly appreciated.Thanks

  4. #4

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    RE: GST 7.7 Brushless conversion help needed

    They burnt up due to cheap batteries. I finally broke down and got a max amps battery and re-geared it as well. I have not had any problems with it burning them up since. I did not use the trans I made a custom one around the matrix tr center diff mount and the custom mount for that application available from RC-Monster.com (which holds the motor) I used the cent diff from the genesis tranny and a matrix tr 66t spur gear and the center diff lock. I used a piece of 2" 90 degree aluminum stock as well as a 2" flat piece of stock and some 1/4 steel brake line to mount the diff carriers to the chassis. My single speed seems like it hits around 50 mph or so, never clocked it so I am not positive on this.

  5. #5

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    RE: GST 7.7 Brushless conversion help needed

    Hi,I had a couple questions I was hoping you could help me with since you already have a converted CEN.I have decided to run the 700kv motor that I already have to get going.I am going to take your advise and run a MMM speed control and will be using 6s lipo battery since I already have a few for my helicopter.I am going to use the stock center diff and gears with a 17 tooth mod 1 pinion for starters just to see where I am and wil work from there.My question is,when looking from the rear of the truck,which gear in the center diff should I have the pinion gear mesh with?The larger gear or the smaller gear.Also,this is a 2 speed trans.Am I going to run into problems like the truck will be running and then shift gears and be all messed up?I really wish it was a single speed so I wouldn't have to deal with those possible issues.Any ideas on what I should do?I work in a machine shop so I will be making my motor mount soon.Do you think I should have the motor mounted above the spur gear or off to the side of it?Any input would be greatly appreciated.

  6. #6

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    RE: GST 7.7 Brushless conversion help needed

    where did this project go? i would really like to see you get thru with it and your original plan with the 10s lipo. 6s is too low of a voltage for that motor.

  7. #7

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    RE: GST 7.7 Brushless conversion help needed

    Hi,I ended up putting a Mamba Monster system in the truck.The KB45-XL just didn't seem to work out for me.I run the Mamba Monster on 6s and the truck is nothing short of an animal.Here is a link to a video of the truck I built doing standing backflips.I am very happy with how the truck came out and how fast it is.It easily runs 50 mph with all this torque.

    http://www.youtube.com/watch?v=6wOXtHVkcnI

  8. #8

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    RE: GST 7.7 Brushless conversion help needed

    i like the setup you have there. its very close to what i was thinking about doing if my ebay purchase ever gets shipped.......... what center diff and spur did you use? spur looks nice and big.

    also, i'm surprised that system can throw that trucks weight like that. i've been planning much more power for it, maybe i can save some $$ on it. how are your temps, expecially bashing through grass?

  9. #9

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    RE: GST 7.7 Brushless conversion help needed

    The truck weighs about 19 lbs and as you can see the motor system has no problem throwing it around.My motor temps run pretty good even on grass as long as I stay with a small pinion gear.On the street I run a 12t pinion.That is what I had on there in the video.If I am going offroad alot, I drop it down to a 9 or 10t pinion gear.The fan I have on there helps alot.The center diff is a 66t spur gear.It is the assembly from a Cen Matrix Arena truggy.It is big as you noted.I will get you an accurate temp next time I run the truck.I can hold on to the motor no problem.If you get a Mamba Monster system,run the gears I am using on 6s your truck will be out of control.I was also planning on a 10s crazy system but it isn't needed.I am using 2 Zippy 5000mah 30c batteries and have all the speed and power I could ever use.I have never had the truck wide open but I would say it runs 45-50 mph at 3/4 throttle with the 12t pinion.I can only take it to about 3/4 throttle right now because the tires at that speed balloon so big and thin the truck gets very squirrely.Feel free to ask any more questions.

  10. #10

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    RE: GST 7.7 Brushless conversion help needed

    awsome. looks like i can even use what i currently have then and maybe not have to buy anything. i currently have an mgm 22418 esc, sentinal 100a 10s esc, and strong motors i have a kb4510xl and a mega acn2240 i believe, i have to double check that modle number, but that sucker is stout and 6 pole ultra high end components.

    i did get the truck yesturday so i can start tearing down and cleaning the nitro smell off. i think is still have my eye on some other brushless equipment, but i will probably start with what i have and go from there.

  11. #11

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    RE: GST 7.7 Brushless conversion help needed

    okay, i'm going to go with a center diff, although i really thought about trying my luck shifting gears thru the 3 speed trans. i prefer simple though. my question is when you used the arena's center diff did you keep the front slider shaft or go to a dog bone? i think i would like to keep the slider but i need to make sure i have the right output from the diff.

    i was going to use a gs sut center diff i have, but the output on the trans won't adapt to my diff for a easy swap. the front shaft is red locktight onto the front diff so i couldn't get it off to look at my options there.

  12. #12

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    RE: GST 7.7 Brushless conversion help needed

    I didn't use the slider shaft because the end on it didn't match up with my center diff.I used dogbones from a Kyosho Inferno ST.They work well.You can also use 2 rear dogbones for the cen.

  13. #13

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    RE: GST 7.7 Brushless conversion help needed

    i'm trying the axles, but they just seem a hair too long for the diff to set right and roll freely. still working on it.

  14. #14

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    RE: GST 7.7 Brushless conversion help needed

    I see RC-Monster have a 2-speed pinion converter for 5mm motor shafts. With that on the brushless motor shaft, no modification is needed besides bolting down a motor-mount like the one from Tekno RC. Did anyone ever try this combo and would a strong (1600kv) brushless motor driving a 2/3-speed gearbox actually work?
    He who dies with the most toys, wins...

  15. #15

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    RE: GST 7.7 Brushless conversion help needed

    i'm sure it would work just fine, i already have the 2 speed pinion i used in a 1/8 onroad. i just didn't want all the extra stuff on there. i finished my mounts and got my motor in. i'm waiting on posting pics once i get the truck rtr, cause then there won't be any changes. i just used the diff that was in the transmission, and i have a cen tr arena 62t spur ordered for it.

  16. #16

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    RE: GST 7.7 Brushless conversion help needed

    Hi there
    I am planning on a similar setup on a Genesi with the stock spur gear and gearbox - with the Tekno clutch adaptor fitted to the engine.
    But how about braking ?
    Do the ESC have an output for a brake servo - or how to i solve this ?
    I am old to nitro and green as Kermit to electrics
    Tks guys and best regards from Denmark
    Niels Vangsoe
    www.nitromekanikeren.dk
    Boca Ceramic Bearings
    www.nitromekanikeren.dk

  17. #17

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    RE: GST 7.7 Brushless conversion help needed

    The Tekno Electriclutch is fine, but it only has space for one pinion. If you plan to use the stock 2-speed gearbox, you'll need both (17t/21t) pinions. I just finished mine. The stock pinions fit nicely onto the outer part of the RC-Monster 2-speed pinion adapter. That sorts out the pinion issue. The motor mount is Tekno-RC's motor mount for Castle motors. Now to figure out a way to mount the 2 battery trays...? (Sorry about the picture quality, its cellphone pics...)
    Braking will be done with the throttle/brake servo via a Y-splitter cable from the Rx throttle channel. The ESC will be set-up with no braking and no drag-brake, that will be handled by the servo. Haven't done it yet, but that is the theory...
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    He who dies with the most toys, wins...

  18. #18

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    RE: GST 7.7 Brushless conversion help needed

    Hi Lomdel
    Tks for the lightning fast reply buddy !
    I was going to use the CEN GSR / Corsa 5.0 clutch bell with 2 pinions on the Tekno adaptor.
    Which kind of clutch shoes and springs would you recomend ?. I guess as soft as possible.
    So its as simple as a Y cabel from the throtle / brake from the receiver and then setting the ESC to no brakes...tks - i cant wait to get on with it and see how it works !
    As for motor mounts i will just make some myselve.
    Tks again - will keep you posted.
    Niels VAngsoe - Denmark
    www.nitromekanikeren.dk
    Boca Ceramic Bearings
    www.nitromekanikeren.dk

  19. #19

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    RE: GST 7.7 Brushless conversion help needed

    The space next to the motor is just a tad too small for a Mamba Monster ESC. Damn! Anyone know of a good way/place to mount the ESC?
    He who dies with the most toys, wins...


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