Converting an HPI RS4 MT to MT2SC, but a little different.
 

A couple weeks ago, I won a HPI RS4 MT on eBay, before I knew CKRC made a conversion kit for the MTs, with the intention of throwing a brushless on it, and just having a fun basher. Now that I have seen the MT2SC kits, I decided to build an SC basher instead.

Here's what it looked like when I got it. (Pictures from ebay ad.)

http://img.photobucket.com/albums/v2...MNm1i9U_12.jpg

http://img.photobucket.com/albums/v2...myM1iEg_12.jpg

http://img.photobucket.com/albums/v2...myBg9bg_12.jpg

So, it came with almost everything aluminum, but it was missing a bunch of stuff (not really a roller if it can't roll... right?) but that was ok. I set a target budget on this build of $300, which is far less than any of the other 4WD SC's out there, especially with as much aluminum stuff that I will be keeping.

I quickly learned I probably should have started with a MT2 roller, but I had the RS4 MT now, so I decided I will upgrade the drivetrain to beefier MT2 stuff. To do that I needed to switch out the arms and some other stuff.

First thing I did to it was get MT2 arms, and since it was missing a couple bearings and ball ends, I got the bearings and upgraded to firestorm ball ends (M3 thread 4.8mm ball, vs 4-40 thread 4mm ball) to go with the titanium turnbuckles that came with the roller (BNIB). While I was at the LHS looking through the parts bin, I found some heavy duty diff outputs, but they only had one pair. I got them anyway intending to order the other set online.

After I put the MT2 arms on, I found that the hinge pins on the outer parts of the arms were different between the MT and MT2, and the LHS was out, so I went to ebay for the rest of the parts I needed.

I got the diffs apart to see what I was working with. The ring and pinions on the MT were the crappy pot aluminum type, so I knew if I was going to upgrade the drivetrain, that would be the first to get upgraded, so I ordered up these:

http://www.horizonhobby.com/ProdInfo...I86329-450.jpg

These are the HD steel ring and pinion gears made for the NRS4 3 Evo (Touring car version of this truck) and are 36/14 vs the 38/13 stock gears. I probably should have gone with e-savage HD gears to keep the stock ratio, but who doesn't want more speed?

This makes the overall ratio with an 11t pinion, ((52/11)*(36/14)) = 12.16:1. If I throw on a 12t pinion, I'm at 11.14:1, and a 13t would be 10.29:1. I think I'll start with the 11t pinion, and see if I want more speed or not. If I need less speed, the only room is to go back to 38/13 R/P, which brings the ratios to 11t (13.82:1), 12t (12.66:1), or 13t (11.69:1) I just want to make sure that whatever motor I get is enough to get things up to speed without melting down.

I couldn't find another set of the HD diff outputs, so I got some stock MT2 diff outputs for the front, and ordered up some GPM front and rear CVDs, and whatever hinge pins I needed.

http://img.photobucket.com/albums/v2...ild/7abd_1.jpg http://img.photobucket.com/albums/v2...ild/7a66_1.jpg

As far as the chassis is concerned, I emailed CKRC to see if they would sell just the chassis plate, and they had a used one just sitting at the shop, so I ordered that as well.

If you haven't seen the build that CKRC did, it's on their website, and a couple other users here have done the conversion too. I want to do a few things different though, and that's why I ordered just the chassis only.

Plans on how I will build this different to what CKRC intended:

- Mount the center gear slightly off center to balance the battery and motor on the chassis better. This will also allow me to mount the battery away from the spur a little bit. I'll need to make my own chassis brace for this, and I will have to figure this one out. I will play around with some CAD files to get it the way I want.

- I will fabricate my own motor mount from 1/4" delrin. I was going to do this anyway for the basher brushless upgrade, and I've already got the theory figured out, I just need a motor to take measurements from to get it just right. Luckily the roller came with the aluminum gear box, which has spots that are perfect to mount everything to, and I don't have to worry about drilling out the bearing holes.

- I will just use Axial pinion input shafts, that are already 5mm, so I won't need to grind anything down. Really I wonder why these aren't included in the CKRC kit. Either these or the E-savage 5mm shaft will save the end user from having to grind the shaft down or drill out the yoke. I emailed them about it, and they are "looking into it."

- I want to use a blitz rear bumper and nerf bars. I haven't seen any of the other conversions do this, so I want to find out how hard it will be to do it. I also want to use either the Slash 4x4 front bumper or something other than the SC10 bumper.

- Not sure on the body mounts, but I will probably just use Blitz mounts.

Other things I need to complete this:

Find some decent basher tires. (I likely won't race it, but want something that can hold up in case I do) I have been scouring eBay for some cheap stock SC wheels/tires, but I might just get some Pro-Line Switches (2.2) and throw them on my custom narrowed axial 8-hole rims. Willing to take some suggestions here; I want to keep my 2.2s but if I can find a decent set of SC wheels/tires for about the same price as just getting 2.2 tires, I would consider it. The 2.2 goosebumps or suburbs look interesting as well...

Get the brushless motor, and/or ESC. I have a sidewinder that I can use, but I would need to re-solder the third wire back on, but I don't know if my iron is up to the task (those wires are basically welded on.) For the motor, I plan on getting something fairly mild. I have the gearing for a high-torque motor, so I will probably get something between 1800kv and 3300kv motor. I have seen some good things about the turnigy orange can motors (5mm shaft to fit a mod1 pinion) and for the price, if it sucks, I can find a good use for it. Need some help with what KV to get, I've never done brushless, but I also don't know how fast this will be on even a brushed motor.

Fabricate some battery hold-downs. I will just use a few pieces of scrap 1/4" delrin, and some velcro straps. Lightweight and easy. I plan to use my 3S 3600 30C lipo, which should be more than enough current capability.

Need a body. I like the Pro-Line Silverado body, but I also like the Dare body. I want a used beat up basher body to use as a "practice" body though...

So, almost enough words, I will try and keep an updated budget status, so that others considering this can see what I did. Of course keep in mind you may see higher or lower prices than this, and your fabrication capability will help save a ton of money.

So, as of today, here's what I have spent to the penny:

$72.33 - MT roller with shipping.
$54.45 - eBay parts (CVDs, HD gears, hinge pins, diff outputs)
$32.55 - LHS parts (Suspension arms, HD diff outputs, bearings, ball ends)
$23.22 - CKRC MT2SC chassis (This was the only used one they had, they usually go for 30 or 40, according to the email I got)
$182.55 so far.

Still plan to spend:

$30 - 35ish - Motor + heatsink
$25 - 35 - Tires
$35 - Body
$90 - 105ish? (would put me at $270 - 285 total)

Had I started with the MT2, I wouldn't have had to get the arms, or the diff outputs, and might have waited on the CVDs. I plan to sell the RS4 MT parts that I didn't use to try and recoup some of this cost, but since it's not a guarantee, I won't count it yet. Also trades and or donations :wink: will help with overall cost.

Comments? suggestions?

More pics, less talk.

I got some of the parts in, so I started getting everything transferred over to the new chassis:

The rear has an aluminum case, and I upgraded to the heavy duty outputs. I rebuilt the shocks with 30wt, and put some Mobil 1 Synthetic gear grease in the diffs (in hopes of a semi-limited-slip effect.) Aluminum hub carriers and titanium turnbuckles, along with the HD r/p and outputs should make the back end nice and tough.

http://img.photobucket.com/albums/v2...d/S5003964.jpg

http://img.photobucket.com/albums/v2...d/S5003965.jpg

http://img.photobucket.com/albums/v2...d/S5003967.jpg

I didn't get the other HD R/P yet, but I started to transfer the front end over as well. I have a spare Axial diff input shaft that I will use for the front so I can use some crawler driveshafts. The HS645 is just a placeholder to check clearance. I'll be tossing a 180oz-in digital servo in it.

http://img.photobucket.com/albums/v2...d/S5003971.jpg

http://img.photobucket.com/albums/v2...d/S5003973.jpg

http://img.photobucket.com/albums/v2...d/S5003977.jpg

For the center diff, I wanted to move it a little over to make some room for the battery, as well as balance it better. The bottom shot shows how far I moved it, with the chassis front on the right side of the pic. The spur still clears the cut out. Now I won't have to worry about the spur eating up the battery.

http://img.photobucket.com/albums/v2...d/S5003969.jpg

http://img.photobucket.com/albums/v2...d/S5003976.jpg


So, I still need tires, body, motor, bumpers, and to fabricate the battery mount, motor mount, and top plate. So there is still plenty to do.
One thing I really like is this thing is lightweight. I think the battery will almost double the weight of the ready to run weight of the truck. I also need to get some lighter springs for it now that it's not carrying around a fatty nitro motor.

FYI the universals you have will take a shit in .5 seconds. See if you can find the MT2SS cvd's

What is the weak point in these? The Pins? That's an easy fix with the right diameter drill rod or piano wire... I tried to search for info on them before I ordered and didn't see any bad info... We'll see how it goes once I get the rest of the parts I need to finish the build. They seem sturdy enough though.

kick ass! i love HPI, and DIY projects so this is just sweet. nice job. keep us posted.
go with the silverado body for sure ;)

Ok, so would you guys rather have stock Slash 4x4 tires not S1 compound or m2 Switch tires?

I've got a deal on a set of stockers from the Slash 4x4, but what do you guys think will be better for overall bashing?


@Stang Killa SS - Ya, I'd love the silverado body, and from what I find, a clear stocker is going to run about the same. I've got a crazy paint scheme bubbling in my head too, as long as I can get the paint masking custom cut...


I am fromt the "built not bought" kind of thinking. I hate building things the way they are supposed to be built, so this is right up my alley. (Look at any of my other builds, no stock honchos, no stock anything really.) Also, my sig says it all: Always modding something...

Hows this project coming along Jens? I like it, looked good when I seen it at BC.

Got some basher Blitz bodies (2 of them, one is in a more bashed state than the other.) and some Masher tires I am going to narrow along with narrowing the Axial beadlocks I have. This is a basher, so these bodies and tires will suit their purpose for the time being.

I am just about to order the motor, and then I will need to fabricate the motor mount, the top plate and the battery blocks, solder the third wire back in to the sidewinder, and then this thing will be ready to fly!

Oh yeah, I also have to get an HPI82020 diff input shaft since the Axial one won't work.


So, for the budget, I spent an additional:

$20 - LHS - 10t Mod1 Pinion, wire for the ESC, and IC2000 for narrowing the tires (will be used for other projects as well.)
$25 - BST forum purchase - 2x Blitz basher bodies.
$21.73 - Ebay - Tires
$66.73 - total spent this round

$182.55 spent before
$249.28 Total so far to date.

I will have to readjust the budget to cover the motor and the material for the top plate and for the diff input shaft. I might still be able to come in under $300, but the motor is going to be most of the remainder. Oh yeah, I also need a little bit to cover getting blitz bumpers and nerf bars, and slash body mounts. That shouldn't be too much, but all the little things add up.

When I am done though, I will have a very nice basher, that is durable (we'll see how the universals do, Gula has me a little worried now), lightweight and quick.

Progess!

Got the M3 Mashers in the mail, and right away went to cutting them to narrow the tires and foam, and I also got the black chrome axial beadlocks narrowed as well:

http://img.photobucket.com/albums/v2...d/S5004002.jpg

http://img.photobucket.com/albums/v2...d/S5004005.jpg

This puts the width at 12" in the front, and a little over 12 at the rear. This would be too wide for an SC body, so I am going to get some SC wheels and tires soon. CKRC recommends slash offset wheels, but I want to "try on" a set to make sure everything tucks, and looks good. For now, the mashers will be my basher tire, to go with my proline Revo Crowd Pleazer 2.0 body.

Next I got to work on the motor mount. After some careful measuring, some delrin, a little speed saw and dremel work, and this is what I came up with:

http://img.photobucket.com/albums/v2...d/S5003997.jpg

http://img.photobucket.com/albums/v2...d/S5003994.jpg

I don't have the motor yet, but the slots are measured for a 36mm motor, and the mount holes are spaced according to what the manufacturer listed as the screw spacing. This is measured so the can sits directly on the plate, hopefully to help keep the motor cool (I'll also have a heat sink and dual fan to help) and keep it stable in the jumps.

I also made the "battery box" out of delrin. I basically set the battery down, marked it's edges, and cut the delrin to length. All sides of the battery box are 30mm tall, which will connect to the top plate (when I make it) so everything will be nice and contained and the chassis and diffs will be nice and stiff.

http://img.photobucket.com/albums/v2...d/S5004000.jpg

So here is how it sits, nice low center of gravity, good proportion of width to wheelbase, and nice and lightweight. (I will weigh it when it's all done.)

http://img.photobucket.com/albums/v2...d/S5003992.jpg

Comments, suggestions?

It looks awesome I think. I cant wait to finish mine, I also plan on using some M2K's with similar wheels, But I will use a different body on mine.

Re: Converting an HPI RS4 MT to MT2SC, but a little different.
 

Bringing this one back from the dead...

A little more than a year ago, I got another MT2 with quite a few aluminum parts already installed in a trade. The plan was to do something similar as above, but with some changes to make things easier.

The "brand not to be mentioned" chassis above was the starting point, but there were some major changes I wanted:

Maintain the use of the stock transmission, but push it further to one side to allow a standard sized stick pack battery to fit on the other side of the chassis.
Make it an easy swap over with easy to find parts. One center drive shaft was kept from the MT2 (86mm dogbone), and one borrowed from the EXO (94mm dogbone).
Make it strong and durable - with the spine and brace design, this mimicks bridge truss design to keep everything super strong.

Problem was this build was thrown to the side, waiting for the chassis, and one prototype chassis is pretty expensive to get cut. Recently the waterjet company I work with had a sale on one-off 1/8" Aluminum parts, so it was the perfect time to get this going.


http://img.photobucket.com/albums/v2...ps6fd4bd76.jpg

http://img.photobucket.com/albums/v2...psfe51a574.jpg

http://img.photobucket.com/albums/v2...ps36dfa211.jpg


The chassis came out looking great, and everything fits well. I still need to get the rest of the spine braces, a new motor (brushless, of course), servo, esc (probably use one of my sidewinders), wheels/tires, bumpers, body mounts, and a body for it, but the base structure is there.

For wheels and tires, I am thinking the HPI Trepadors look pretty cool, and since this will be a basher, I think they will work fine. For the body, I am thinking about the Proline "True Scale" Silverado body for it. (Notice above I was thinking about the other silverado body 3+ years ago...)

I'm considering offering this conversion kit for the MT2, but I have to get pricing together.

More updates to come in the next few weeks. (Rather than more than 3 years apart...)

Re: Converting an HPI RS4 MT to MT2SC, but a little different.
 

Very nice, love modding these platforms. The chassis work looks great. I can say I'd be super interested in a motor mount. I got around it with my projects, but would love a single mount like a 1/8 buggy.

If you get bored of the truck set-up, they make killer rally cars too.

http://i472.photobucket.com/albums/r...06081112-1.jpg

Re: Converting an HPI RS4 MT to MT2SC, but a little different.
 

I love modding the RS4 based stuff, I've done quite a few projects over the years with the platform, and have never been disappointed. I have something crazy up my sleeve that I am working on that uses the drivetrain from the RS4. Keep an eye out for that. "thumbsup"

I designed this to use the motor mount from the Exceed 1/8th scale cars:

http://ep.yimg.com/ca/I/yhst-1419739...7_2270_1778016

The mounts are inexpensive and also provide a heatsink, so it made sense. I initially tried mounting this type of mount to the stock chassis, but there were already so many holes, it became swiss cheese pretty easily.

Plus, I wanted to stretch the wheelbase for the SC bodies as well as get the motor a little more outboard to make room for the battery on the other side.

Like this?

http://www.rccrawler.com/forum/rally...rally-car.html

I actually was originally planning to make this into a rally car using the proline SC sized Focus ST Rally body. I bought one, and painted it up, but the paint was not done correctly, and looks like crap. I may try to salvage the body with some paint on the outside and cover it up with "sponsor" decals.

I have one of the Exceed 1/8th scale platforms as well, so if I get the rally body looking decent, I can put the Silverado Body on the Exceed.

Re: Converting an HPI RS4 MT to MT2SC, but a little different.
 

look at my PRO 4 build where I'm using the front diff from the MT2 "thumbsup" ....

http://www.rccrawler.com/forum/non-c...o-4-build.html

Re: Converting an HPI RS4 MT to MT2SC, but a little different.
 

Hey jens anything happen with this lately? Im about healed up now and going to start something similar with my mt2 and a savage flux 2350 motor and esc.

Re: Converting an HPI RS4 MT to MT2SC, but a little different.
 

Not a whole lot since the last update. I am going to try to get something on this done by the end of Jusne

Re: Converting an HPI RS4 MT to MT2SC, but a little different.
 

"thumbsup" You better update soon. A guy locally is basically giving an MT2 roller away and I had the exact idea. Maybe I missed it, But what are you using to connect the center diff to the front and rear diffs?

Re: Converting an HPI RS4 MT to MT2SC, but a little different.
 

No center diff in this rig ! Simplest method would be using stock rear shaft and a maxx slider for the front.

Re: Converting an HPI RS4 MT to MT2SC, but a little different.
 

I actually used one of the MT2's existing dogbones and the other came from the EXO. Keep spinning mass down, and leave more room for everything compared to a sliding shaft universal joint.
I designed the chassis to place the center gear where those two dogbones would fit. From post #11 above: