CR01 first steps

[mrklaw]

Hi - really want to build a CR-01, and want to check a few things before I start out. Hopefully I've picked up something from reading up on here and other places.

I'm not looking for a comp crawler, just to have a bit of fun with. Scale-ish but not too fussy about applying some 'artistic license' with that.

servo: Thinking to buy the hitec 645MG servo as its not too expensive and has good comments from people. I'm assuming its easier to just buy two of them for 4ws, there are no size limitations for the rear set?

4-wheel steer: worthwhile to help with the bad turning circle with locked diffs? I have a spektrum DX3 (original, not 3.0) which can apparently be modded to give a full 3-position 3rd channel, so I'm wondering if I can get more control over the 4ws - eg 2ws/4ws/crab? Don't know what I'd need for that, so looking for some guidance on that. or should I just set it up with a simple y-cable (link to where to get one would be helpful!) and have it on all the time and use the 3rd channel for something else?

esc: I need recommendations for a decent (but not crazy expensive) esc that can handle driving two steering servos possibly off one channel via a y-connector (in case I can't get better control or I want the 3rd channel for lights/winch). needs instant reverse and preferably some drag brake.

paint: How about paints? The toyota seems to want 'normal' paint not spray for the wheel arches - what kind would that be, or can I just spray the aerosol into a pot and paint with that?

body in general : how easy to fit alternative bodies? Can I pretty much buy any Tamiya 1/10 (or compatible) and get it to fit somehow? For some reason the CR01 makes me want to try all kinds of bodies on it. I think something like the Lunchbox would go really well, or a small truck to make it like a monster truck, and I'm sure there are more.


Anything else I need to bear in mind when building it? Don't want to be heading back to the LHS during the build - want to make sure I have everything I need.

[mrklaw]

oh, and whats this about BEC I'm reading about? do I need one with 4ws? No idea what one even is - can't seem to find one on UK online stores either.

[skid]

My personal experience is the 645 servos will work, but still left me wanting more power. I am very please with the Hitec 7995's. $110 a pop, but worth it. And you'll most likely need a external BEC. Castle Creations makes a good one rated at 10 amps. Most speed controller's are only rated around 3 to 5 amps. For speed controller's, I love my Tekin FXR's. Very versital.

On the DX3, you shouldn't have to do anything for rear steer. Plug the rear servo into the 3rd channel and the button on the grip will controll it. It's a momentary with it returning to center. I ran the button with the side of my thumb when driving.

[mrklaw]

thanks.


so as standard (centre position on the switch) on the DX3, is that 2WS or 4WS?


Also, this BEC stuff confuses me. Can't find any mention in the UK of these, nor about wiring them in etc. Are there ESCs with them built in that'll handle two servos? If not, any recommended ones (guess I'll have to import)

[gordb]

Just my 2 cents, but I'd try it with 2WS first. Even with locked diffs, it's a huge amount of fun, and it's easy to add the second steering servo if you find you want it. With the single servo, you can probably get away without an external BEC, just go for a speed controller with 5amps on it (many of the Tekin and Novak ones have that).

And it probably fails you're "not crazy expensive" test - but I love my Novak Goat crawler setup in my CR-01. Worth every cent and if you luck out with a good Tower discount, they're not that expensive.

[mrklaw]

I'm in the UK so for example, a rooster is £90 over here - about $145. Or I can import one from ebay for about £55. Thinking of going with the rooster mainly because of the built in BEC being pretty good.

Is it easy enough to retrofit a servo later on? Its not something that needs to be done during a build?

[860Crawler]

I agree on the 645MG. I have that as well. Its pretty good in most situations but every now and then I'll be facing downward on the rocks with all the weight on the front tires and the 645 is a little too weak to move the tires.


Also, that Lunchbox body is going to be a bit small on the CR-01 since the LB is considered to be a 1/12 scale and the CR is 1/10.

The rear fender paint I used was regular Pactra model paint in black it worked fine and hasn't come off. You dont need to paint a perfect edge around the fender since Tamiya provides some black stickers to line the upper edge to make a perfect looking fender.

Also, if it hasn't been explained the BEC helps supply sufficient voltage that your ESC alone would not be able to provide if you are running 2 servos.

[gordb]

Originally Posted by mrklaw

Is it easy enough to retrofit a servo later on? Its not something that needs to be done during a build?

It's relatively straight forward to do after the fact. The fact that the axle is 4-linked means you just twist off a few links/shocks and you can work on the axle assembly just like at build time. The servo mount/servo screw right onto the axle itself, so it's then just a matter of running the wire back and sorting out the eletrics on top of the chassis.

Worst case you might have to undo a few screws on the axle - but it should be pretty minor.

[quickster47]

Here is an example schematic from Castle Creations that shows how to wire up their BEC. It is pretty self explanatory and can be applied to most BEC wiring.

Carl

[mrklaw]

but if i get something like a novak rooster crawler, surely that has enough of an internal BEC to handle 2x hitec 645s?

And i'm still confused by the dx3. Does switch A physically move the rear servo full left/right/centre, or does it mix with the steering input so the rears move proportionally with the fronts? The manual makes me think the first one. If so i might stick with 2ws for now

[860Crawler]

when you click the 3rd channel button, its going to turn the front in conjunction with the rear.

[Golic]

With regards to building the kit, two invaluable tips I picked up from reading this forum both relate to the drive train. 1. The screw pins that lock the front and rear diffs will make the axles bind if screwed all the way in. 2. The two large bearings that fit onto the spur gear in the centre transmission need to be pressed all the way on. If they are not seated properly the transmission will be tight when the cover plate is screwed on. Thanks to the people who posted these tips (you know who you are) if I find the articles again I'll post the links.

[mrklaw]

thanks for that one.

Going to take me a while to pay for all of this - worked out it'll cost about £500 all in, with a DSM receiver, couple of 645 servos and a rooster esc, so i'll take it easy and absorb some more information

in the meantime I've bought a losi mini rock crawler to have some fun with

[mrklaw]

I'm thinking of painting it yellow, but I don't know which yellow to use - are most of the yellow ones on here bright yellow (PS6), or camel yellow (PS19)?

so 1 can of white for the roof, 2 of yellow for the body, (I have some black for the fenders), and 1 smoke for the windows (do you try and make it translucent, or completely opaque?).

I think the manual mentions silver, but I don't know what for (grill?) - should I buy a can (what colour) or just some enamel paint and a paintbrush.

[TrickyNickro]

That smoke for the windows is going to be very runny, keep that in mind and go light when you're painting. One or two coats should do it, unless you want them very dark.

[mrklaw]

thanks, i'm going to need to practice my technique to get a smooth coat too

[m&mkrawler]

Very nice custom scaler...made me do a double-take when I saw/heard the video. I'm not a big fan of the 'Bronco' body but I like yours...nice job...

[krapulax]

While most of your questions are legitimate I think you're fretting way too much.

About paints.

First you need to know they're not compatible, so one paint may actually peel off the other one. I had this bad experience. Check first.
Painting with a spray can paint sprayed in a little jar and using a brush does not work because spray can paint is very diluted and it'll run like crazy all over the place. Some companies make polycarbonate paints they sell in little jars for use with an airbrush. Again, some are already diluted to be sprayed, so you need to check that (as explained above they can be very diluted). Tamiya paints (that come in jars) are not diluted so they're good to paint with a brush straight out of the jar.

About esc.
All current escs on the market have some decent BEC componentry. It is common these days they can hold up to 6A which is enough for powerful servos. I use a Novak rooster crawler which has the drag brake feature as well and it didn't cost the earth. It can also drive two JR 8911 servos which have each about 25kg of torque (this means that if you lock the wheel in a crevice so the wheels can not move, the servo will actually swing the truck around the wheels, this is how powerful they are). They are the most expensive servo on the market, but worth every penny.
You need twin steering, otherwise you won't be able to manouver in tight spots at all. As simple as that. In competition this will cost you valuable points but even when just having fun it is very annoying not to be able to go ahead and having to manouvre back and forth to line the truck up for the next obstacle. This is not always possible, so double steering is a must.

Hitec servos are useable, but quite weak. I used them in my Ford F350 and it could not even shift gears if the truck is not moving. No problem with the JR.

About the third channel.
On a wheel radio the third channel is like the auxiliary on heli radios. It will give you an "on-off" switch on a third (or extra) channel. In aero, they're used to pull the landing gear up for instance. Not sure how you'd use the rear steering feature with it, since it doesn't have a proportional control or even left-right control.
Having to switch to twin steering I decided to try a heli type radio (which I already had, I admit) which offers more channels than you'll ever need for a crawler. I don't have any extra features like winch, etc on my rig (nor do I plan to) but the heli radio has enough channels to give you for that if you want them. On top of that, the heli radio is so much better at everything than the wheel radio for the crawler, I will never go back. You can for instance use the throttle stick (on heli radios that doesn't spring back) to hold a very low constant (indeed proper crawling) speed when going down steep slopes for instance and jerkiness on the throttle can flip the rig easily, especially with speedos with drag brake. It's pretty much like in a real 4WD going down slope with "driver assist" or engine brake in low range (if you're familiar with real 4WDs). Or you can even set up the throttle to give you more forward than reverse stick travel if you want.

One more thing. Your DX3 uses DSM1 which can lose contact every now and then and is bound to line of sight control. This is not a big problem but it can be if the receiver comes unbound (loses connection) for a fraction of a second at the wrong time. I know, because I have the same radio and I use it in on-road racing. There, we have line of sight all the time to our cars, so not much of a problem, but I still had some close calls coming fast into corners.

One real problem I had with the CR01 was the crappy phillips head screws which have to be screwed using lots of force and strip heads so easily it's not funny. This problem can be mitigated to some extent if you use a japanese standard phillips screwdriver (JID) which has a different design to all other phillips screwdriver tips (it is designed to bite in the screw head rather than jump out when the screw bottoms out). Even so, some of the screws are in such an awkward position it's impossible to get a screwdriver square in the head, so you're bound to destroy them. Get some decent allen head screws and a ball end driver (many options here).

And if looking for upgrades, I can recommend only one as a must, and that's driveshafts. Get some decent ones (many options here from Tamiya or other companies) because the stock plastic affairs that come in the kit are just crap. Even with the stock silvercan motor they pop out, they twist, and one of mine had a bad joint from factory so couldn't even be used (one of the steel cross joints had one arm shorter so it popped out ad nauseam). Poor QC from Tamiya I guess, but still annoying to me. I modified some traxxas joints initially (I had them lying around the house) but eventually I went to tamiya steel joints and had no problem ever since (the traxxas modified shafts were good too but induced a more acute angle at the diff end, limiting the amount of downtravel I can use before I had driveshaft binding).

About bodyshells not many will fit without modifications. One that fits even better than the Tamiya shell is the proline bushwhacker shell which has the correct wheelbase for the rig (the Tamiya shell doesn't, surprisingly enough). Don't know about the other shells tamiya makes for this chassis.

All this I have found out on my own, (I read later that a lot of people had the same problems), so I would encourage you to stop fretting and go ahead, buy the kit and take it from there.

Good luck.

[mrklaw]

Many thanks for a great reply. Yes, I am probably fretting too much, but thats just me - new area of interest plus need for too much detail

I think I'll just get on with it then


BTW, are there standard drop in replacement driveshafts now then? I'd read about the plastic ones twisting so that makes sense to upgrade while building.

bodies I think I'll make up the Land Cruiser as the box image and then worry about new ones.

[krapulax]

The Tamiya upgrade shafts (different front and rear) are of course drop in as you'd expect. I expect likewise from other companies' products intended for the CR01.

Anything else (products not intended for the CR01) would probably need modifications (the Traxxas shafts I used had to be shortened and the output/input holes had to be rounded as they come with flats).

The stock bodyshell will rub everywhere and generally be absolutely hopeless. Looks a treat though. People cut it progressively until it ends up looking like the comp rig shells (i.e. not much shell left). I made some extra high flexible body posts that raise it about 40mm (yeap, that's 4cm) above the highest setting you can have with the kit posts, and it finally clears the wheels in some sort of reasonable way. Still rubs occasionally though, but then again my suspension has such a long travel and allows for so much twist that I had to cut the sides of the bull bar or the wheels would have been stuck in it.