Converting my CRT .5
 

First off, hi. I am Eric. This place seems to be full of knowledgeable people and I hope to learn a lot here.

With that out of the way let's move on to what I came here for. I'm going to convert my CRT .5 since I'm tired of nitro. I'm going to be using the RCBros conversion kit, a Mamba Max, and a Medusa MR-036-050-3300V2-5. I got most of it sorted out. Except for one thing, gearing. I know I'll be using the stock spur so I'm going to need to know what pinion I should use. The truck will be run on 3S LiPos and use the stock 2.2 wheels.

Welcome! Your setup sounds almost exactly like mine, except for the conversion kit used (I made my own mount, ESC/rx tray, and batt tray) and I stuck with stock size tires. I think you'll be very happy with your proposed combo. As far as gearing goes, I have mine using a 14T pinion, which sets the top speed at around 35mph. Seeing as you are using 2.2" wheels, you may want to gear down a little more, probably 12T or 13T because the larger tires will have a higher roll-out; that will keep you in the ~35mph range.

BTW: There are some R/C calculators (link in my signature) that may help in choosing the right gearing.

Thanks for the reply. I've already ordered the kit and it should be here in a few days. Is there anything I've missed that I should know about the conversion?

I assume you're gonna stay with the steel spur? If so, a hardened pinion is a must (Mod1 pitch).

Not related specifically to the conversion, but you might want to check the diffs. In stock form they come pretty much empty. Some people have also upgraded the shocks; Revo shocks with jato springs in the front, and front 8th scale buggy shocks in the rear. Makes for a better ride from what I noticed.

I was looking into the shocks. And I heard that with brushless you should run a higher weight fluid in the centre differential. Is this true?

I do. There is so much torque that the fronts balloon like crazy otherwise. Personally, I like 120k, but most people think that is wayyy too thick. But, I mostly bash so the extra snap is nice. 120k is just enough so you can wheelie when you want to, but more controllable than a locked center diff. For racing, you'd want more control, so thinner fluid would be better (probably around 30k).

I only have 10k in my center diff and I can still wheelie from a stop, sometimes it flips right on its lid. I run a RC-Monster motor mount, homemade aluminum battery tray to hold the lipo on it's side. I run a Medusa 36-50-4800 on 2s 5000mah 25C, Mamba Max esc, still have the stock shocks with 50weight, and 10th scale buggy rear tires(essentially stock, same size, just have differest tread). I gear for no more than 35MPH to keep it sane but have geared it for over 40MPH, esc gets a bit warm though. I have also run 10th scale truck tires but I like it better with the stock size.

In both my crt.5 I run 5-15-7 and I bash so this set up works well for me. I also have 1/8 ofna front buggy shocks in the rear and Revo in the front w/blue jato springs

Mag do you mean 7 (f) 15 (c) 5 (r) - normally its is lighter oil in the rear I thought...

Yup....another example of my 40 yr. old mind working backwards!:whistle:

What size screws do I need to use to mount the motor?

m3X8's work fine, just check the depth before locking it down and running it.

Thanks.

Also, what 1/8th shocks wrok best on the rear? Anything extra I have to buy does it just bolt on?

I use 1/8 buggy front shocks from Ofna .......http://www.amainhobbies.com/product_...ed-Shock-Set-2 just assemble and go!

Also, the Revo shocks on the front work great as well so much stronger and smoother than the stock ones....here is a thread on them....http://www.rc-monster.com/forum/show...t=crt.5+shocks

Or if your a cheapskate like me and a few others you can run the Jato composite shocks.

CRT.5 has to be one of the most widely owned RC's on the forum.

I'm running the composite GTR's on the front. I need something for the back.

1/8 front buggy shocks. Just about any will work. You'll want to use light springs, whatever you can find.

I like the ofna lx front shocks with yellow springs for the rear of the crt.5. I just trimmed 1 coil off the spring to get the ride height correct. I ran a l can and a 3s, so my truck was heavier than some.

I heard the Turnigy LiPos have enormous wires. Would I still be able to solder Deans ultra plugs to them?

Sure thing. Just make sure you have a good iron and you can make some clean solder joints.

Can I use these shocks on the rear?
http://www.amainhobbies.com/product_...ucts_id/139648

Maybe too big normally just use the 13mm shocks

http://cgi.ebay.com/NEW-OFNA-Front-S...360167370970QQ

I use Mugen front shocks on the rear and it's a perfect fit, I just had to dremel the ball edges a bit to fit in the a-arm. So, whatever is around that length should fit. Be careful though, if you get "big bores", the bore diameter may be too big to clear the upper turnbuckle.

BTW: I would look at some ebay chopshops for a set of new shocks, probably be quite a bit cheaper.

Which Mugen shocks do you use?

Eric,
Brian uses front mugen buggy shocks on the rear, and probably revo or jato shocks on the front...

Yes, Mugen fronts on the rear, and Revo shocks in front.

These are great cheap shocks for the rear of your crt.5:

ebay link to shocks

i use nothing but deans and have great success soldering to a deans. larger heat shrink might be needed.

Eric,
Go for the ofna lx one shocks that everyone is suggesting. They are cheap and work very well. The 13mm bore is perfect for the crt.5. I would say its safe to assume a good 80% of us use those exact shocks ever since go-ride posted the shock mod in this forum. I have no complaints with them.

Thanks.

Any ideas on where to mount my antenna? And how? Also, I got a version 1 Medusa and I would like to know how much of a flat spot I should grind on the shaft.

Now I'm mad because the stupid hexes that hold on the centre diff bulkhead have stripped. I really don't want to cut into the chassis plate...:grrrrrr:

Try to find a small easy out or a small left handed drill bit.

Take a dremel cutoff wheel and cut lots of stuff with it until it has worn down to about 3/8" diameter (or smaller). Then you can cut slots in the heads of the screws (to use a flat blade screwdriver) without cutting the chassis.

I save all my worn down cut-off wheels for just this reason.

I already got them out...I still need to know how much of a flat I need to grind into the shaft on my Medusa.

Flat spot doesn't need to be very big. It only needs to be enough for the end of the set screw to sit flush against. As for rear shocks, I went with a set of Jammin CR 13mm fronts on mine. Here's what mine ended up looking like


[YOUTUBE]TixENpf1Lns[/YOUTUBE]

Cool. Where did you mount your antenna?

Here's the thread on my build. You can check out pictures there. The mount is a Tekno antenna mount. It's the same a the Mugen antenna mount. It allows you to put your antenna just about anywhere.

Ofna has a conversion kit comming out and, from the sounds of it, the OFNA SCRT10 short course truck will utilize crt.5 parts. (or mini Hyper ST parts)

The SCRT10 sounds pretty nice (10th scale 4wd) so I will most likely be getting one for my b-day :intello: