RS4 MT Overhaul

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orcusomega

orcusomega

Well-Known Member
Messages
653
Location
Royersford, PA
Well, I got me an RS4 MT last week, and its pretty cool - but I don't like the SHORT run time, and I didn't like the .15 it came with.

RS4MT-05.jpg


So I swapped in an OS V .18!

RS4MT-11.jpg


Aside from just swapping in the engine, I also noticed that the clutch bells on the .18 and the standard ones we use on the Savages is the same - so I got rid of the 12T and dropped in a 13T - we'll see how well this runs! Last weekend I took it for a quick spin, and in literally 50 feet, the new spur was totally wasted. Lets hope this lasts longer :)

So the run time on this was also an issue - so I went wall-shopping at the LHS and found that the Revo 150cc tank is a pretty close fit in the stock tank location - so with a little grinding and some nlyon rod stock, I was able to shoe-horn in the 150cc tank - 3x the normal capacity!

RS4MT-06.jpg


Another thing that was ****ing me off was the terrible throttle linkage - it just plain sucked. So I did the Ofna Mod to the MT too:

RS4MT-08.jpg


I cut out the windshield so that I can refill the tank from the outside of the body in case I decide I want to bang on it at the local track - I can tell though, this thing is gonna be prolly too fast...All in all, I think it came out pretty well!

RS4MT-07.jpg


I still have a bunch of things to do - need to water-tight the RX, CA the tires to the rims (on the quick shake-down run, I threw the tires off all 4 rims within the first 20 feet), I am going to definately need to beef up the suspension and steering, but it should be a fun little truck :)

Here it is next to the Savage:

RS4MT-03.jpg


Hope this helps another MT owner!

Bob
 
looking good, obviously by my username, you know I'm a nmt fan, ive built over a dozen of these, big block conversions, onroad conversions, savage diff conversions, you name it
youll have fun with these trucks
they only make one spur gear size, so you can only change the clutch bell size, but you really don't need too on these
but anyways, have fun, and ask me any questions if need you too
but i doubt YOU will need too
you seem to exceptionally knowledgeable when it comes to RC
 
Well, let me get your opinion then!

I found that the center diff on the MT2 uses essentially the same slipper clutch parts as the Savage - so I am waiting for the parts to come, and I am going to convert the center MT2 diff to all steel spur - it looks like it should work, based on the exploded diagrams and part numbers from HPI. If I can pull that off, the world will get a whole lot faster :)

That said, this thing can clearly go fast, but I need to figure out a bumper, and how to toughen this bugger up. Obviously, the turnbuckles and the steering components need to go - the PO put in CVD front and rear axles but the OEM center dogbones are still in place. I would like to get more travel out of the suspension - recommendations on shocks and towers?

Thanks for commenting - I hope I don't annoy the hell out of ya with all my questions :)

Bob
 
i had the mt 1 yes the ornigal old bugger i had a hpi .18 5 galons old and it would be smokin my savage down the road
 
its been awhile since i messed around with a NMT
i had trouble with the turnbuckles and rods ends popping off, so i put some lunsford turnbuckles and dubro captured rod ends, solved that problem and made it alot more durable
gpm racing used to make a nice alum. front bumper for it..try asiatees.com or hobbyetc.com for the bumper or of course...ebay
as far as shock towers and shocks, there isnt much, i used the alum shock towers from gpm racing and alum shocks from hpi, never had any problems
i was going to try using the NMT2 towers and shocks, because the shocks are longer than the original NMT
also, as far as i know the slipper from the NMT2 and savage use the same parts...
i have an original hpi 2speed for the NMT thats extremely rare, i never could get myself to take it out of the package
i had one on my onroad NMT convo, and if you can get one of those 2speeds your speed cravings will be satisfied, also the 2speed can be rebuilt using savage 2speed parts
 
Wow great links - thanks! I was trying to find goodies for the MT, it is fast but doesn't look like it will survive me behind the wheel for long LOL

I was trying to find a parts interchange - I want a front bumper and the MT2 looks like a good idea - can I just use the front brace from the MT2 on my MT? (example) then put the MT2 bumper on that?

Any help is appreciated - and if you want to part with that 2-speed, make sure you give me a call first :)

Bob
 
orcusomega said:
Wow great links - thanks! I was trying to find goodies for the MT, it is fast but doesn't look like it will survive me behind the wheel for long LOL

I was trying to find a parts interchange - I want a front bumper and the MT2 looks like a good idea - can I just use the front brace from the MT2 on my MT? (example) then put the MT2 bumper on that?

Any help is appreciated - and if you want to part with that 2-speed, make sure you give me a call first :)

Bob
Click to expand...
lol, i knew you were going to want the 2speed, i have two NMT's in boxes that ill put together eventually, ill probably use it one of those

as far as that brace goes,it looks just like the ones i have, minus the front brace thingy..this is the one i have..
http://www.asiatees.com/display.php?HPI-Nitro-MT-Parts-Hop-Ups&brand=HPI&model=Nitro MT&id=832&pid=1
it looks like the NMT2 one, so I'm sure it will fit and then just bolt the stock nmt2 bumper on..if it doesnt work, i suppose you could just send it back

I'm sorry if I'm not much help, like i said, its been awhile since i messed around with the nmt's, I'm just working on memory here and thanks to "mother nature", my memory isnt that great lol
back in the day, there was huge amounts of parts for the NMt
maybe, you will get me motivated to build one of my old ones, so ask away, i actually enjoy helping...the nitro mt was my first nitro ride..ahh, the memories :)
 
hmm, its not working,
just look at the nitromt catagory, i have the front braces, they look the same but don't have the front brace part
 
Well, I pulled out the MT last night, and put it up against my RS4 3 Evo - and there are a ton of differences!

Actually, that is a GOOD thing. I have this spare RS4 Evo, so I can use that to upgrade to the MT2 parts slowly a bit at a time. It looks like I can put the MT driveline on the MT2/RS4 Evo chassis and go from there. Biggest difference is the front of the chassis, where the front diff mounts to the chassis. On the MT2/Evo, there are 2 extra screws, and that is where the bumper mounts. The LHS has a bunch of MT/MT2 parts (in the 50% off bin woohoo!) so I am gonna go up there and see what I can get to get the bumpers and assembly at least - I need to figure out how to Bob-Proof this as much as possible. What I lack in driver skills I make up in ability to abuse :)

So - any reason I can't run the RS4 2-speed as an MT? Run smaller tires, and the .18 - should be not too bad. You mentioned that the 2-speed gears are the same as out of the Savage trans - mess with the gear ratio that way maybe?

Bob
 
i found a link in hpieurope site on how to put a two on your existing trans....but the drawback was no slipper. check out hpieurope's site or i can try to hunt down the list for ya. you'll be surprised what you find on their website...new how to's and everything
 
well, i don't know if the gears are the same,
what i do know is that hpi makes a rebuild kit for the savage 2 speed, it has springs and that little ball thingy and the plate...i used those same parts to rebuild the NMT 2speed
if you can your hands on a 2speed, that with the .18 engine will be all the speed you can handle...the main thing here is to "bob-proof" the truck
just get all the alum crap you can, that will make it tough
ive beaten the crap out of nitromt's, stock there fragile, but beef them up and they handle anything
i wouldnt put too much money into it, because you can buy a new NMT2 for like 250 bucks
 
Well, sorry for not putting up any updates - been crazy lately :)

So, I got another MT2 off eBay, and the initial intention was to use it for parts - I was looking for upgraded turnbuckles, etc and this rig had all the upgrades I was looking for:


What I did not know, was that the truck would come with 2 custom chassis that were drilled for a big-block conversion. I did not take pics, but I dropped my Picco 26 in it, and the thing was WAY too fast, even with low gearing... So I swapped my .18 back in, and then blew the motor :(

I did learn a few cool things along the way:

1) I am going to rebuild the old MT into an MT2, since I got a TON of spare parts, and will be able to make the conversion without buying anything more. This will give me the better radio box, etc.

2) I wanted to get the upgraded turnbuckles, but found a cheaper alternative. The Lunsford turnbuckles were $25 for the set, but did not include the rod ends. I went to the LHS, and found that the Stampede camber links are the same size - and only $7/pair WITH the HD rod ends. So I grabbed a bunch of those :)


3) Unlike on the MT where I used a Revo tank, I was able to find an Ofna tank that almost drops in place to go from the 75cc stock tank to 150cc. I spaced the front mount up about 8mm, then used nylon rod to build the rear mount. Took a total of about 10 mins total.


4) I don't like the rotary carbs at all. The arms are a weak point in my opinion, and if they snap, whatever the truck is GONE. I will get some pics of the Ofna throttle mod I did to keep the load off that rotary carb.

All in all, progress continues, but I will make a point to take more pics as I go along!

Bob
 
LOL! As a matter of fact, I did :) At our last bash, the motor let go :( So it was time for a new plan...

I decided that it was time to try my hand at brushless :) When I was looking at the price of replacing the motor compared to a brushless conversion, I figured it was worth the try.

I started off by stripping everything off the chassis but the bulkheads and center diff. Since the MT2 uses the same spur gears (literally) as the Savage, I just needed to find a pinion that matched. The Savage uses a Mod1 pinion, and since I went with a 1/10th scale motor, it had a 3mm motor shaft and not the 5mm shaft that the larger motors use. I also picked up an adapter to sleeve down the diameter of the Mod1 pinion - worked like a charm.

When I was at the LHS, they had a Dynamite ESC and 5800kv motor for $100 - DEFINATELY made it worthwhile - since I needed the motor anyways. Using a piece of clear plastic to make the template for the motor mount, I made an aluminum mount out of 2"x2" aluminum angle (1/8") and mounted up the motor:

One thing that had me worried was the fact that the MT2 uses a large radio box that supplies structural support by tying the front bulkhead to the center diff to the rear bulkhead. Well, this had to come out for the battery, etc. In order to keep the chassis rigid, I put in an old set of turnbuckles to replace this rigidity:

From there, I just added the steering servo (flipped, since it would otherwise interfere with the LiPo battery), ESC, etc. Last thing to do is build a way to hold the battery in place - but that should be easy! Here's how she looks now:


So I hope to be able to take it out tomorrow as the weather permits. I have a few more things to upgrade, namely turnbuckles, etc but I can do that as time goes on - I am looking forward to taking it out on 3S LiPo!

Comments welcome,

Bob
 
excellent bob, excellent! what a good job, i like the turnbuckle idea, should work well, let us know how she runs
i toyed with the idea of making one of my nitromt's brushless, looks like ill have to make that happen now!
 
Well, the pics were taken quickly, and at 1-2 AM so they suck :) I have more things in the works when time permits (it never does, thats why I work on them at 2 AM). There are a bunch of changes\improvements I want to make:
- I don't like the motor mount - I am going to make a new one that will allow for adjustment for different pinion and spur sizes, but this will work for now.
- The motor needs an additional brace in the rear - I don't know if it NEEDS it, but I want to support both ends to prevent deflection and damaging the spurs
- I need a good battery box :) For the time being I made an adapter to go from the Deans connector to a Tamiya (GAH - I know) since I have a bunch of NiMH packs I can play with while I work out little details. Then the 3s LiPo needs a home...
- The stock turnbuckles suck, and I keep forgetting to bring the damn thing with me to the LHS to measure them up to Traxxas units. I know, but Traxxas has a TON of super-strong turnbuckles hanging on the wall and they are easy to use, etc. Easier than making home-grown ones.
- I need a good place to mount the antenna, but need to see what else ends up getting moved around before I go down that road - who knows, might end up moving everything all over the place, so thats a real minor issue in the overall scope of things.
- I might also move the transmission... I was looking at the overall design, and MIGHT mount the transmission to its own plate, then move the rear dogbone to the front, front to rear etc to give the battery pack more room to be positioned more towards the middle - but I need to figure out how that will affect the steering servo, as well as the dogbone angle (the front bulkhead is slightly tilted up on the nose)

The best thing about all this is nothing is permanent - I can unbolt everything and go back to nitro if it doesn't work out - doubt I will tho :)

Bob
 
Will do :).

I actually got it running last night -
[youtube]6cozgwQYeq8[/youtube]

This is with a 7.2v NiMH 2500 mAH battery zip-tied to the lateral supports - i still need to work out the battery location for the LiPo. Turns out i will definately need to relocate the trans to the left or the balance us WAY to the right. I have 2x2 aluminum angle so I am going to see if i can make a one-piece trans plate with motor mount without making any changes to the trans in case i need replacement parts i don't want to have to make my own spares. I am also going to try to flip the dogdones to move the motor/trans forwards to make tons of room for the battery - need to grab a cvd tho - angles are tight!

For the record, Traxxas 3644 turnbuckles can be used to replace the crappy stock ones - you need 3 sets (6 total) and you will need 4 misalignment spacers for the front.
 
Last edited by a moderator:
Sorry for the "Blair-Witch" video quality, but it is hard to drive and shoot video at the same time :)

I did not take it off the deck yet, since the grass was very wet, and it is not weather-proofed yet - just making sure everything was working!

If you look at the video at 1:30 or so, you hear me say "What?" - for some reason the ESC reset itself - when you reset the ESC, it does the steering left-right, then makes some tones -I figure I have a wire loose there somewhere or the ESC might be in trouble already (HOPE NOT!)

hpinitromt said:
if you end up with a nice motor mount, make two and ill buy the other one off you :)
Click to expand...

I found some motor mounts on fleabay, and I have two coming - we'll see about how strong they are, but they are pre-machined for the adjustable pinion size, etc. Worst case scenario, I figured that they would work as a template to machine out the 1/8" stock I have - they should be here in a few days, and I can add that to the pile of things to be done in the next 2 weeks :)

Bob
 

After running nitro for a while, I have to admit, some of the nuances are getting annoying. It is a pain to tune, keep tuned, replace glow plugs, yada yada yada. Not to mention fuel (nitromethane) is $40/gallon!

So I was running the MT2 a few weeks ago, and the motor lets go. OS .18 motor, the truck was a SCREAMER. Unfortunately, even if I had a new motor to put into it, it takes forever to break them in in order to be able to run them...<!--more-->

So I was at the local hobby store looking at possible motors, and they had a Dynamite Fuze electronic speed controller and 5800kv brushless electronics set on sale for 2/3 the price of a replacement engine - so it came home with me :)


To start the process off, I removed all the stock turnbuckles and steering rods and replaced them with Traxxas units. There are a lot of aftermarket turnbuckles, for like $25 for the rods PLUS $20 for the ends - but they are not as good as, or as easy to get ahold of, as Traxxas units - nearly every hobby store carries Traxxas gear! So for the record, the proper Traxxas part is #3644, and they run about $6.50 a pair, and you need 3 pair (front and rear camber links and 1 pair for the steering links).



With that taken care of, it is time to strip down the chassis. I removed everything except the front and rear bulkheads. Since the battery is so large (3S LiPo muahahah) I need to move the transmission over to the right and forward. So I flipped the front and rear dogbones around to move the trans forward, and moved the trans to the right using a custom aluminum plate. It was pretty easy, actually, and made a TON of extra room.



Once the trans was relocated, I moved the motor mount back in line using a custom motor mount I made out of 2"x2" aluminum angle.



An important note: the MT2 uses the same spur gear as the Savage, and it needs a Mod-1 pinion to properly mesh, which has a 5mm motor shaft. In order to put the needed pinion onto the 1/10 motor, which has a 3mm shaft, you need an adapter, available from MyAtomic (among others). I started with an 11 tooth pinion and a 53 tooth spur - mostly because I don't know how much torque the Fuze motor has.



Once the motor was in, and the motor mount in place, it was time to reinforce the chassis - and this was initially a head-scratcher. The original MT2 used a radio tray that tied in the front bulkhead to the center trans to the rear diff - but I can't use that anymore since I need the space for the electrical components. So, instead I used turnbuckles :) From the rear bulkhead to the trans, I used the turnbuckles from the HPI Savage - they worked like a dream. From the front bulkhead, I used Traxxas 3744 turnbuckles. One of the nice things about using turnbuckles is that you can set them to be the exact length you need, without all the measuring and drilling, etc :)

With the center trans in place, and tied into the front and rear bulkheads, and with the motor in place, it is time to mount the steering servo and receiver box. For the steering servo, I used aluminum uprights to move the servo in closer to the front driveshaft and forwards from its original location. I had to do this for 2 reasons - #1 I am still trying to make room for a large battery tray, so the servo needs to be as far forward as possible and #2 the original angle of the steering rod to the actual bellcrank is gradual in the original manufacturer's configuration, but with all the moving around, it becomes quite steep, and a lot of throw was lost to vertical angle between the servo saver and the bellcrank. To somewhat compensate, I used a M3x20mm screw to go through the rod end, then a M3 locknut on the other side before going into the bellcrank - this elevates the mount level and make the steering more crisp. For a servo, I used an HPI SF-2 I had lying around on the workbench, and trimmed off the rear most post from the front steering support plate. If you look (right-most picture), the servo is VERY close to the driveshaft - this was inevitable in order to make the steering functional :)



(continued in next post - hit the character limit LOLOL)
 
Now that the steering was setup, it was time to get the receiver in place and figure out how to make it as weather resistant as possible. So I used an RPM radio box that is typically used in Savage Mid-Tank conversions, and dropped it in right in front of the motor. This worked out well, since the motor bracket extended forwards, and the RPM box has a leg underneath that I was able to shave off to make everything level. Only problem was an antenna mount, which I made out of 5/16" aluminum square stock and bolted to the top of the box. I don't like the way it looks compared to everything else, but I can certainly revisit that later if it bothers me enough :)



Right behind the motor, I installed the ESC. I did not use the foam tape they supplied, though. Since I am forever tinkering with my RC's I needed something that would hold tight and still be removable. I used, instead, high-strength fastening tape from Grainger, similar to the stuff they use to attach EZ-Pass'es to the car window - works like a CHARM! I zip-tied the wires in place to make sure that there was no way they would get into the rear drive-shaft, and ran the wire to the receiver.



Last but not least was the battery tray - the whole reason why the chassis had to be revamped. Using more of the 2"x2" aluminum angle, I fab'ed up a 3-sided box that will hold the battery in place. I did not add the 4th side, or the top, since I am going to use a Velcro-strap to hold the battery in the box onto foam padding. I had to do it this way to accommodate many different sized batteries. This will work for now, I am waiting for my Flux battery boxes to arrive.



So how does it run? In a word- AWESOME! It needs some tinkering to get the balance and suspension tweaked but all in all it is a blast! The gear mesh ended up spot-on (not sure how LOL), and the ESC combo works great. I may put in a 3500kv motor to get some more torque out of the setup and put the 5800 into a street RS4 Evo, but that's another project for another day!



Comments, as always, welcome!

Bob
 
that is looking nice, i was going through all my nitromt stuff the other day, i tink ill be doing this project too, since all the hard work was done by bob!
 
That truck rocks with power.

I like how quiet it is caz it won't interfere with my ipod :jamout:
 
I have been waiting to really open it up - weather has not been good. When I did take it out into the street, i ended up losing a tire and the pinion and sleeve - thank GOD I was able to find them!

I don't like the battery box - there are two screwheads in the bottom, and I don't want the LiPo anywhere near them - so I am waiting on the Flux battery boxes - should be here tomorrow...

The Vorza motor mount is NICE - if you are looking at a buggy conversion, it looks like this will work beautifully :). I am going to try to make an adapter plate that will mount the Vorza mount on it so that you can use the chassis mount sliders for adjustment to different pinion sizes - we'll see how that goes, prolly not until after the world finals though.

Bob
 
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