Mwe's mrc turned mini monster build

[JBcustoms]

still have some of the 3" wide aluminum plate I used when building my first crawler, thinking of doing another now that I have better fab skills. I built my first with a jigsaw, drill, and large file like you have. I totally understand being on a budget and not wanting to spend money, just use what you have laying around. Just keep at it and you will be happy with the final results! Here is my first build for ya if you want some more ideas, building a chassis from scratch isnt too difficult.

first crawler project (Ebatch)

Anyways, keep up the good work, cannot wait to see it finished!

[mwe-maxxowner]

Not as much as I am! The thing is, I'm not trying anything that can't be undone here. So, we shall see how it goes. If it isn't ideal, I'll drop back and punt...after I've finished it. Lol. Once the shocks arrive I can really get to work. I have a body and tires I can slap on it for now, but they won't be what I want. Those things will come later.

[mwe-maxxowner]

What is it about a chassis that can control torque twist? I think I recall someone saying they used the hr chassis and it eliminated the torque twist for them. It doesn't use the stock lower plate though, so no go for me.

[JBcustoms]

I think its the link geometry that helps prevent the torque twist, but im not 100% on that. I do know the upper link design on the mrc doesnt do so well and thats why most go for a true four link design. The pivot at the axle on the stock upper link just allows it to flop around.

I was originally drawn to rc crawling by the customization that can be done. Make something and try it out, if it doesnt work then try something else! No two crawlers are alike, each has their own personality and capabilities.

As for yoir earlier qiestions on axle gearing, whether or not to do the overdrive, I would say keep them stock for now and see what speeds you get from the trans swap. I know those have two gearing options internally, start with the low option and if it isnt fast enough for your tastes go for the higher gearing, and if that still isnt enough start playing with pinions and spur gears.

Keep it up, I havent wrenched on mine in a minute, I need more funds!

[mwe-maxxowner]

Well, if I remember correctly, this tranny with the gears flipped is even lower than the mrc tranny stock. So I think that's a no go. I do like, however, that if I wanna go back crawling, if lowering the pinion/spur isn't enough, I can flip the tranny gears and lock the diff and be right back to it. I did like crawling this thing, but I just haven't in a while, and like yo change things up now and then.

I also kinda wanted a foffer. With paddles and horsepower, this'll pretty much be a foff truck.

As to the 4 link, I can see that. I can see how the single pivot point on the axle would make it twisty. That may be my next upgrade. I think the sticky about common upgrades has some information on an easy 4 link upgrade. Not sure if I can find places on the axles, however, to mount shocks, four links, sway bars, and the suspension links. Maybe time to make a truss?

[JBcustoms]

Copied from a merv tech site: Stock E-Revo Trans gear ratio is 1.94 to 1. If you swap the input gear and idler gear, the trans ratio is 3.74 to 1.

The losi trans is 7.5 to 1, so the losi trans is lower than the merv trans in both setups.

This obviously doesnt take into account the pinion or spur gears, but if you had the same p/s and motor on each trans, and ran the lower 3.74 ratio, the driveshafts would be spinning almost twice as fast than a stock mrc, which will increase speed considerably.

[mwe-maxxowner]

Ahh okay. Dunno why, but I was under the impression it was more like 9:1 with the gears flipped. Not sure why.

[JBcustoms]

Was just doing a little research into the pinion/spurs. The mrc runs a 14/60 combo stock, and the merv runs a 28/50 stock.

So, stock losi ratio at p/s is 4.29 to 1 stock merv at pinion spur is 1.79 to 1.

Stock losi through p/s and trans 4.29x7.59=32.56 to 1
Stock merv through p/s and lower trans 1.79x3.74=6.69 to 1

According to these calculations, this thing is going to haul a$$! You may want to try a smaller pinion and larger spur.

[JBcustoms]

That just reminded me of doc brown talking to marty in back to the future, "when this thing hits 88mph, you're gonna see some serious $h!t!!!"

[mwe-maxxowner]

Haha. I think the stock 50 spur is still on there, so I was gonna start around 9 or 10t pinion on 2s, then try 3s. I'm also going to run everything through the speed calculator at rcscriptasylum to see what I'll get before I test it out. I may also seriously limit punch and torque until I see that everything holds up okay.


Traditionally, I would have tossed in a 3s with a 4 pole motor, programmed to 100% power in all aspects, nailed the throttle, and watched it torque twist itself into a pretzel . I guess I'm getting older :/.

[mwe-maxxowner]

Where is it that you fellas find things like 3mm barrel nuts, or coupling nuts, or whatever you wanna call 'em?

[T_Tank]

usually find things like that at ace hardware for me at least, other hardware stores should have metric hardware to.

As for things like standoffs amazon is a good place to look hotracing has a good variety of long standoffs you can use for links or chassis braces and if you can't find the length in hot racing's selection axial usually fills in the gaps other then that a careful use of a dremel can get the exact length you need or use a couple of washers. I prefer the dremel method for strength an less things to go missing when doing rebuilds.

[mwe-maxxowner]

Fastenall and ace neither have stuff that small, or metric. I'd need enough washers to span between the chassis plates, lol. And some very long screws. I'll check out hot racing's standoffs and see about ordering some stuff. They had 3mm standoffs for my extended Merv chassis in various sizes in the kit.

[89redranger]

Another option for cross members and standoffs, buy K&S 3/16"x0.049" aluminum tube, cut to the length you need, then tap the ends to M3. Works great. Obviously, for M2 you'll need smaller tube. For cutting fluid I use the thinnest oil I can find in the house. Aluminum already likes to gall, and doesn't need any help with "sticky." The better the chips fall out, the better the cut, and the less taps you get stuck/break. A friend of mine tells me that alcohol works better for aluminum because it's less-than-water viscosity flows well, and alcohol oxidizes the chip (makes perfect sense if you know what alcohol does to aluminum...). I personally work indoors, am deathly allergic to alcohol, and haven't tried it.

If cutting threads isn't your thing you can use K&S 3/16"x0.035" tube with M3 or 4-40 all thread through the tube and chassis, and nuts on either end. I did this on my daughter's car to retain the factory side mounted body posts. I simply drilled them out, and threaded them over the M3 threaded rod till they hit the nuts on either side of the chassis.

For your applications, a combination of both styles of standoff may need to be used. That's your call. Regardless, nice to see a real attempt at an MT. I threw in the towel when I had a pile of parts that didn't seem to cooperate no matter what configuration I tried.

[mwe-maxxowner]

Would the m3/m2 taps be available at a regular hardware store, or an auto parts store? I'm not afraid to cut threads. M3 is what's used in the stock "nut" between the upper shock mounts, right? Where is the k&s tube found?

I like either one of these options, because it allows me the custom length I need without splicing multiples together. I dunno how readily I can find 3" coupling nuts wherever I look.

[89redranger]

I buy the smaller metric taps one by one from my local hobby shop. They are fairly high quality, kind of expensive (like $8 each with the matching required drill bit), but are the only ones that seem to last and cut nice threads. The ones sold in sets are usually mass-produced by the 1000's, and often are a little lower quality.

The tube I buy at the same LHS or Ace Hardware. My local Home Depot and Lowes stopped carrying aluminum and K&S products.

And yes, that "threaded standoff" between the shocks is M3. Another source for pre-made standoffs and spacers is MCS Direct. The smallest they stock is M3, but I find a lot of neat stuff through them every time I get on their site. Their standoffs and spacers are sold in different lengths, can easily be trimmed to the length you need, the threads chased with a tap after, and used.

Oddball projects lead to oddball requirements for hardware sometimes...

[JBcustoms]

I was getting my m2 and m3 hardware from the Ace my gf was working at, but not all Ace's carry all the available hardware as they are independently owned. If you can speak to the manager or owner about talking to their Hillman or serv-a-lite hardware distributors, you may be able to order a box or two of the size you are looking for on a special order.

[mwe-maxxowner]

School me on taps please. I'm looking on MSc industrial right now, and figure if I decide to order standoffs, I'll get a tap also. There are several styles. Plug, bottoming, and taper. What style will I want? Or rather, what is each style desired for?

[89redranger]

Without typing a book this is the best you're gonna get-

Taper Taps have 7 to 10 thread chamfers to distribute cutting action over many teeth and the taper also acts as a guide in starting.

Plug Taps, with a chamfer over four threads, is most widely used in through holes and where there is sufficient room at the bottom in blind holes.

Bottoming Taps are made with just enough chamfer for starting in the hole, only 1 to 2 half threads. As the name implies, it is designed to thread blind holes to the bottom.

Taper taps are what you will want for 99% of our parts and builds.

[mwe-maxxowner]

Gotcha!