Mgt brushless conversion

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olds97_lss

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I've never messed around with RC gearing before. Is the difference between a 15t and an 11t pretty dramatic? I'm more after acceleration since I want to use this thing for wheelies and jumps
Depends on the spur, but yeah, that's a pretty big jump usually. The larger the spur, the smaller the jump in ratio. With a 46T center diff/spur, a few teeth one way or the other will be pretty noticeable. Tire size also makes it more noticeable too.

Like my my kraton (1/8th MT with 3.8 wheels/taller tires), going from 18T to 20T was a big bump.
On my typhon (1/8th buggy), going from 15-18 wasn't so noticeable, but noticeable just the same with top speed.

Both of those I think have 50T spurs/center diffs. The tire size is what makes the changes more/less noticeable on those.
 

HarryJohnson

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Depends on the spur, but yeah, that's a pretty big jump usually. The larger the spur, the smaller the jump in ratio. With a 46T center diff/spur, a few teeth one way or the other will be pretty noticeable. Tire size also makes it more noticeable too.

Like my my kraton (1/8th MT with 3.8 wheels/taller tires), going from 18T to 20T was a big bump.
On my typhon (1/8th buggy), going from 15-18 wasn't so noticeable, but noticeable just the same with top speed.

Both of those I think have 50T spurs/center diffs. The tire size is what makes the changes more/less noticeable on those.
Oh right on, thanks for the info. Fingers crossed I'll actually be able to drive up a curb with the 11t. It chokes with a 15t, but hauls hairy butt on the top end down the street. If it's not that, then maybe my cheapo amazon ESC I bought sucks.
 

Greywolf74

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Welp, I thought the old tires and wheels looked soooo cool, but they don't stand up to the new motor and battery.

View attachment 155873

Can't find anything monster trucky with a 3" inner diameter, and definitely not a 3" inner diameter and a 6.8" outer diameter.

I found these bad boys on amazon for a decent price, so we're gonna try them out. In the meantime, my kid still wanted to drive the thing so I raided my parts drawer and... well, I'm not proud of it, but it made him happy enough:

View attachment 155874

But an interesting thing happened- I realized I had a different problem. With the large tires, this thing couldn't get out of its own way on the low end. If it rolled to a stop in thick enough grass, it would sometimes glitch out and not have enough low end to get going again. I've got a 2000kv motor in there with a 4s, so I was suspecting gearing. This confirmed it. It ripped with small wheels. I currently have a 15t gear on the motor and a 46t(largest this conversion will fit without hitting the chassis) gear on the center diff. The motor gear (pinion?) is 5mm 1p and it was difficult to find anything smaller than 15t available, but I think I managed to find a 11t, so I was going to try that. Would that make much of a difference? I have a lot of experience with the 1:1 4x4 world and normally we would go lower gears in the diff. Is that a thing on RCs? Will I be hard pressed to find lower gears for such old diffs or are they pretty much universal?
Genrally on RCs the gearing is done through the pinion and spur. Some kits you might find some pinion gear for thats a different tooth count maybe even a ring ring but its not terribly common. I would think a 2000kV motor with a 3.06 gear ratio would run just fine even with the big MT tires. What is the exact motor, ESC, and battery combo you're using?

As for tires, heres a whole bunch of MT tires that should work although IIRC you'll need some 17mm hex adapters to make these work. At least most of them, some may have other hex sizes but most are 17mm
 

olds97_lss

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Oh right on, thanks for the info. Fingers crossed I'll actually be able to drive up a curb with the 11t. It chokes with a 15t, but hauls hairy butt on the top end down the street. If it's not that, then maybe my cheapo amazon ESC I bought sucks.
What motor/esc do you have?
 

HarryJohnson

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I would think a 2000kV motor with a 3.06 gear ratio would run just fine even with the big MT tires. What is the exact motor, ESC, and battery combo you're using?

What motor/esc do you have?
I wasn't sure if my kid would like this type of setup or not, so I went amazon cheapo.

Motor is a Surpass hobby black 4076:
https://a.co/6BccoP1

ESC is a Surpass 120A brushless ESC
https://a.co/fzboxdR


I figured if they played with it enough, we'd upgrade
 

olds97_lss

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Last edited:

HarryJohnson

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Yeah, you would have wanted a 150A esc. 120A is what's used in something the size of the stampede 4x4 or outcast/kraton 4s 4x4. The motor should be fine though.

The 8BL150 is a fairly cheap esc, similar to the blx185 that arrma used to use in their 6S stuff.
https://www.amazon.com/Hobbywing-QuicRun-Waterproof-8BL150-Brushless/dp/B09FYPW65D

Can get them off ebay for $100:
https://www.ebay.com/itm/295040859358

Less if you go with aliexpress and wait a month.
Ah, that explains it! 150A here we come
 

olds97_lss

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That's still not an overly robust esc, but should work better for you with that size of motor. With the other esc, I'd stick with 36mm motors vs a 40-42mm motor. 36mm motors are usually for smaller/lighter vehicles, unless you go with a long one (3680+) like the TP motors. Although, those motors like a LOT of amps...

The MGT is on par with the savage/savage x/savage flux in size/weight, so a 150A esc should do ok in it. It now runs an ELH-6S which I think is similar to the 8bl150. It does run a higher kv motor though, but it's a 4074 sized can. They used to run castle based esc's, but I think they run hobbywing quickrun based now.

If you really want to beef it up, you can go with a hobbywing max6, but not sure you care that much. lol!

I thought associated/thunder tiger made an e-version of that at one point. Not sure what motor/esc they used if they did.

Looks like the thundertiger mt4 came with a similar esc in it:
https://www.dollarhobbyz.com/products/thunder-tiger-1-8-k-rock-mt4-g5-ace-blc150c-brushless-esc

https://www.bigsquidrc.com/thunder-tiger-k-rock-mt4-g5-monster-truck/

Also appears that they deviated quite a bit from the "MGT" structure... lol
2022-1121-thunderTiger-mt4-g5-roller.jpg



More info about that one:
https://shop.thundertiger.com/produ...uck-k-rock-mt4-g5-brushless-6406-f-rtr-no-ess

The roller showing the photo I found:
https://racingcar-store.myshopify.c...k-rock-mt4-g5-complete-roller-rolling-chassis
 

HarryJohnson

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That's still not an overly robust esc, but should work better for you with that size of motor. With the other esc, I'd stick with 36mm motors vs a 40-42mm motor. 36mm motors are usually for smaller/lighter vehicles, unless you go with a long one (3680+) like the TP motors. Although, those motors like a LOT of amps...

The MGT is on par with the savage/savage x/savage flux in size/weight, so a 150A esc should do ok in it. It now runs an ELH-6S which I think is similar to the 8bl150. It does run a higher kv motor though, but it's a 4074 sized can. They used to run castle based esc's, but I think they run hobbywing quickrun based now.

If you really want to beef it up, you can go with a hobbywing max6, but not sure you care that much. lol!

I thought associated/thunder tiger made an e-version of that at one point. Not sure what motor/esc they used if they did.

Looks like the thundertiger mt4 came with a similar esc in it:
https://www.dollarhobbyz.com/products/thunder-tiger-1-8-k-rock-mt4-g5-ace-blc150c-brushless-esc

https://www.bigsquidrc.com/thunder-tiger-k-rock-mt4-g5-monster-truck/

Also appears that they deviated quite a bit from the "MGT" structure... lol
2022-1121-thunderTiger-mt4-g5-roller.jpg



More info about that one:
https://shop.thundertiger.com/produ...uck-k-rock-mt4-g5-brushless-6406-f-rtr-no-ess

The roller showing the photo I found:
https://racingcar-store.myshopify.c...k-rock-mt4-g5-complete-roller-rolling-chassis
That's some good info! The new chassis definitely looks lighter and more nimble. I'm currently running mine at 4s since primarily a 5 year old is going to be driving it and it was easier to lay everything out without thinking about running dual batteries.
 

Greywolf74

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Sounds like Olds has you on the right track. My first thought that prompted me to ask you what ESC/Motor?battery you're running is because it sounds like you're experiencing some cogging issues. If thats what the problem is then a proper 1/8 scale ESC is needed.
 

HarryJohnson

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Sounds like Olds has you on the right track. My first thought that prompted me to ask you what ESC/Motor?battery you're running is because it sounds like you're experiencing some cogging issues. If thats what the problem is then a proper 1/8 scale ESC is needed.
I had to look up what cogging was. Yep, that's definitely what's going on right now.
 

HarryJohnson

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So this thing is turning out to be an impressive learning experience for me. Got my new esc, got lower pinion gears just in case I need em, got my new wheels buuuut.... New wheels don't fit. They're 17mm and I assumed that's what this truck had since I only saw 12mm and 17mm wheels being sold. Turns out my truck has 14mm hex hubs?? Anyway I can't find any adapters for 14mm to 17mm, so I'm guessing/hoping that they use the same axle size and I ordered some 17mm hex hubs to try and slap on there.

I'll find out Tuesday if my gamble was right.. I think at this point though, I'm probably into this thing for the same amount as if I bought a new 4-6s 1/8 rtr basher new and I haven't even bought radio gear for it yet (been running a spektrum setup that I stole from my sct). Learning a lot though, so I've got that going for me I guess?
 

cbaker65

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So this thing is turning out to be an impressive learning experience for me. Got my new esc, got lower pinion gears just in case I need em, got my new wheels buuuut.... New wheels don't fit. They're 17mm and I assumed that's what this truck had since I only saw 12mm and 17mm wheels being sold. Turns out my truck has 14mm hex hubs?? Anyway I can't find any adapters for 14mm to 17mm, so I'm guessing/hoping that they use the same axle size and I ordered some 17mm hex hubs to try and slap on there.

I'll find out Tuesday if my gamble was right.. I think at this point though, I'm probably into this thing for the same amount as if I bought a new 4-6s 1/8 rtr basher new and I haven't even bought radio gear for it yet (been running a spektrum setup that I stole from my sct). Learning a lot though, so I've got that going for me I guess?

The 21 & 4.60 versions were 14 mm an the 8.0's were I believe to be a 23 mm hex!
 

Greywolf74

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So this thing is turning out to be an impressive learning experience for me. Got my new esc, got lower pinion gears just in case I need em, got my new wheels buuuut.... New wheels don't fit. They're 17mm and I assumed that's what this truck had since I only saw 12mm and 17mm wheels being sold. Turns out my truck has 14mm hex hubs?? Anyway I can't find any adapters for 14mm to 17mm, so I'm guessing/hoping that they use the same axle size and I ordered some 17mm hex hubs to try and slap on there.

I'll find out Tuesday if my gamble was right.. I think at this point though, I'm probably into this thing for the same amount as if I bought a new 4-6s 1/8 rtr basher new and I haven't even bought radio gear for it yet (been running a spektrum setup that I stole from my sct). Learning a lot though, so I've got that going for me I guess?
Maybe this will help

https://www.rctalk.com/forum/threads/mgt-17mm-hex-hubs.108113/
 

HarryJohnson

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So I ordered these: https://www.integy.com/st_prod.html?p_prodid=6008&p_catid=29

I didn't want the extra 6mm spacing, so I *think * I got what I needed. They show up next week sometime
1669923216463.png

I also did some math. Mistakes with guessing and checking parts (and ordering new ones to fix the mistakes) have landed me right about the cost of just buying an RTR Rival... lol.

BUT- I learned a ton and got to work on it with my kids, so I'm still pretty happy with going this direction.
 

Greywolf74

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So I ordered these: https://www.integy.com/st_prod.html?p_prodid=6008&p_catid=29

I didn't want the extra 6mm spacing, so I *think * I got what I needed. They show up next week sometime
View attachment 156249
I also did some math. Mistakes with guessing and checking parts (and ordering new ones to fix the mistakes) have landed me right about the cost of just buying an RTR Rival... lol.

BUT- I learned a ton and got to work on it with my kids, so I'm still pretty happy with going this direction.
Its all about the adventure :)
 
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