Big Rock budget big rock 4S BLX

[maddmatt02]

So the other day I thought it would be cool to record my emaxx blasting through our pumpkins in slow mo as it flew off of the jump. First round was a success but the 2nd pumpkin was just too solid still so now I need a chassis and braces for the maxx. Also I kinda hate working on it these days because there's just so many screws and hard to reach nuts (RPM bulks, etc) that I decided for now to sacrifice the truck to build something else. I also smoked the cheap esc that was in the senton mega the other day. Landed after jumping over my truck again and just made a big ol smoke show and the 120A I had in the box as a spare is pretty crappy. once rolling there is no delay in additional throttle but from a stand still there is a TON of lag before it gets going. so instead of 2 crap trucks I'll build one good one.

I went over the exploded views of the big rock and senton to see everything that was different. I am going to skip plenty of it for now but heres what I'm thinking, anybody think I should do anything else? (this is the short list because it's trying to be "budget")

*HD 17T input gear on the rear (might go to the 13/37 setup front and rear when not back-ordered/if needed)
*BLX driveshaft/center bearing (haven't checked if I have the provision to mount it but both chassis has same part number but I'm guessing maybe old ones didn't new ones do... just like the new/old front skid having same part #s) And I cant tell from pics if they spline count for the shaft/inputs are the same...
*BLX 32P spur/slipper (If I can find it anywhere in stock...)
*Granite/Big Rock body posts
*MAXX chevrons on 14mm RPM stablemaxx wheels (probably need to)
*Fast Eddy rubber sealed bearings everywhere

I am going to try and fit the pro line c10 thats on my MAXX, think it will work the senton body sits on the maxx and looks like a huge SCT... wheelbase lines up pretty good. going to steal the waterproof 120A 4S esc and 2250kv 4074 out of the maxx.

for wheels and tires I have some stock old maxx wheels with the chevron tires and then I have some 23mm hexes and MGT 8.0 wheels I currently run on the MAXX but I don't think either offset is any good so I'll probably get some 14mm stablemaxx wheels and swap over the chevron tires.

eventually will either get the springs for the big rock or swap over to different shocks like the alum HSP ones on ebay that I think Megasty linked to on this site elsewhere. front shocks leak bad and if I try and tighten too much the o rings bunch up/pop out so I either need new cartridges/o rings or new shocks or something.

Will run on 3S until I get some 4S batts that will work. my pair of 2S I run in the maxx uses bullets and it might be tricky to make both work in the senton chassis. I have an idea but not sure it will work yet.

 

[bicketybam]

Go with the BLX diffs and input gears. I think you will trash the mega ones.

 

[Jerry-rigged]

Go with the BLX diffs and input gears. I think you will trash the mega ones.

X2.

The mega 17t/47 won't hold a 1/8 motor on 4s.

 

[ptr1ck]

Mega stock won't even hold up to 3s.

 

[maddmatt02]

Is it the ring or the pinion (input or diff in RC speak I guess) you're breaking? I thought everybody breaks the input and they have a HD 17t input for the megas. I can't get the 13/37 right now at least not from amain I thought they said backordered. I'll ask the LHS when he could get them when I head there later. Ours is a mild brushless setup(read: cheap) and it's held up to 3s fine so far.

 

[bicketybam]

Is it the ring or the pinion (input or diff in RC speak I guess) you're breaking? I thought everybody breaks the input and they have a HD 17t input for the megas. I can't get the 13/37 right now at least not from amain I thought they said backordered. I'll ask the LHS when he could get them when I head there later. Ours is a mild brushless setup(read: cheap) and it's held up to 3s fine so far.

For me it was the teeth on both the 17t input gear and the Mega ring gear that would chip or break.

 

[Jerry-rigged]

Yes, the shaft will snap, with mild power. But a 4s powered 2050kv 4074 will blow the teeth off the 17t pinion after a few run.

 

[ptr1ck]

Mine has wrecked both the front and rear inputs on 3s, 3000kv. I now have the HD input shafts in there. Hope they hold up.

 

[maddmatt02]

Yeah like I thought I could get the diff but not the input. That one's out til 12/28 I think he said so I'll have to try the HD inputs and just put the punch at level 1 and hope for the best for a month or so.

 

[maddmatt02]

I wonder if the plastic/composite gear itself is any tougher on the HD input gear... maybe it's the input breaking first then one that's damaged the leftover pieces and/or damaged input gear itself is what takes out the diff ring gear? Wishful thinking I know but we'll see. Ordered my stuff today but I leave for cali again for work Wednesday so I won't get back and actually build the truck until about dec. 3rd...

 

[bicketybam]

I wonder if the plastic/composite gear itself is any tougher on the HD input gear... maybe it's the input breaking first then one that's damaged the leftover pieces and/or damaged input gear itself is what takes out the diff ring gear? Wishful thinking I know but we'll see. Ordered my stuff today but I leave for cali again for work Wednesday so I won't get back and actually build the truck until about dec. 3rd...

Wishful thinking for sure.

 

[maddmatt02]

I understand but I have no other option until the parts are available. I'm actually going to see how long stock everything will hold up tomorrow because even if I break it I won't be home to care for a while. Still running sct wheels though because like I feared the maxx offset doesn't come close to working. It's not even "not optimal" it just "won't work" lol. Luckily I can still find some old stock of the 14mm stablemaxx wheels.l but I have to re-learn what that offset is to make sure they'll work.

 

[ptr1ck]

The correct offset is same as 2wd Stampede front, which I think is front or rear of a 4x4 Stampede. Just run some 12mm hexes like the Duratrax https://www.towerhobbies.com/cgi-bin/wti0001p?&I=LXHADZ . I have Teknos 12mm that work OK because they clamp even though they fit a little loose on the pin. I may run the Granite Voltage wheels https://www.arrma-rc.com/part/AR550014 next time I buy some. The tires are a little bigger than what comes on the Mega but is 12mm hex.

 

[maddmatt02]

I have the duratrax adapters on my list. Have a 2wd pede set also I'll check out for one end to try. I hope when the granite body mounts show up they have longer posts that drop into the bulks. Swapping senton posts front to rear makes my body sit level because the hood is higher on my bed but I wish the body could sit a little higher because I have to notch both ends for the bumpers.

 

[maddmatt02]

Alright well I got it all setup with stock everything, 48P gears and all. Running 5400 50C 2S packs, ended up running the 6 pole 2650kv 4268 with a 28T pinion. I had to make 2 new holes for the motor though because any way of mounting it using even one included hole seemed to hang the can too low for the module to slide in. I lowered punch a bit and went out and just gave it a test run and man this thing RIPS! On 4S I can go about half throttle and any more it seems (at least sounds like and it's too dark to see) the tires are ballooning and hitting the body. I would have to say I was easily doing 35-40 around 60-70% throttle though. Seems reasonable since same gearing on a 2600kv 3660 does 39 on 3S.

Here's a few pics of the setup (ESC is mounted better now). I thought I might get to finally use my top kick but I don't think it'll work. I think I might try and get something closer to the width/height of the sct setup because while I like the look with the MT tires, I like the more scale look of the smaller wheels, even though when you lift your actual truck you don't install 12" wheel spacers...

 

[Jerry-rigged]

I wonder if the plastic/composite gear itself is any tougher on the HD input gear... maybe it's the input breaking first then one that's damaged the leftover pieces and/or damaged input gear itself is what takes out the diff ring gear? Wishful thinking I know but we'll see. Ordered my stuff today but I leave for cali again for work Wednesday so I won't get back and actually build the truck until about dec. 3rd...

I think the plastic is the same between the 17t/47 and 13t/37t. The main difference is the 13t/37 has bigger teeth, which makes it stronger.

The HD denotes the shaft of the input is metal. The Mega input is all plastic.

 

[Jerry-rigged]

I run that same motor in a 2350kv in my Typhon. Motor has some serious power, and likes to run a bit hot. my 40** barely fits in my Granite, I am surprised you were able to get the 42** can to fit.

 

[maddmatt02]

I didn't take a pic of it but imagine you are looking at the pinion, it's usually pretty centered up/down. Along the bottom going around the holes c-clockwise I added one more hole to the right and higher up then I had to make a notch in the upper holes I had already slotted. Raised the motor a little more than needed though. Might glue in a shim to support the end of the can if it seems like it will cause a problem. Going to try and speed test it and see how she flys later today. But I have a toddler and also have to pack for 3 weeks today.

 

[bicketybam]

I didn't take a pic of it but imagine you are looking at the pinion, it's usually pretty centered up/down. Along the bottom going around the holes c-clockwise I added one more hole to the right and higher up then I had to make a notch in the upper holes I had already slotted. Raised the motor a little more than needed though. Might glue in a shim to support the end of the can if it seems like it will cause a problem. Going to try and speed test it and see how she flys later today. But I have a toddler and also have to pack for 3 weeks today.

You are going to strip your spur. Be really careful.

 

[maddmatt02]

Oh yeah, it already didn't look too happy with the 3660. I have the punch turned down and ease into it slowly. I get on a plane at 5am tomorrow anyways so if I break it today or not I wouldn't play with it for weeks.