CAT Grader in 1:14 with M-Series controls

[JensR]

Dear all,

as I'm new to this forum, maybe allow me to introduce myself. I've been building R/C cars for over 20 years now but only started with serious modifications and own designs when the Crawler craze (TLT-based) first hit.

I've always had a particular interest in earth-moving machines, particularly graders - from horse-drawn to the most advanced concepts.
I wanted to build one in about 2005 - but I wasn't quite there yet and it remained a rather hopeless CAD model ;)

In the meantime, there are now a number of grader models, often based on simple modifications of the Bruder Grader - I wanted something a bit more substantial with as many functions as possible - without going to the top-of-the-line like the 1:8 O&K in Germany or the CATs I've seen here. Wow!

No mill or lathe or budget for hydraulics obviously meant I had to cut back on something. As I wanted good operation, I threw scale realism pretty much out of the window.
It took a lot of planning, but I dare say that I have achieved my goal of building a relatively affordable grader with basic tools that still performs well.

'll post a few pictures, but if you want to see more, please follow this link to a gallery I have set up, it roughly goes along the build process:
http://flickr.com/gp/22070130@N07/13BERN

The grader uses the cab and bonnet (which will be extended eventually) of the Bruder toy. The machine itself is considerably larger, though. In 1:14.5 it is just within the 3m width-limit that makes it street legal in the EU without special permit. In 1:Tamiya, it has a few inches to spare and fits with the trucks quite nicely, I think.

http://farm6.static.flickr.com/5183/5664881586_c675a37057.jpg
http://www.flickr.com/photos/22070130@N07/5664881586/in/set-72157626598857828

The construction is based around aluminium profiles (as is obvious). As power tools, only a drill press, a mitre saw and a jigsaw were used. Everything is bolted together, mainly with stainless M3 cylinder head screws. The main frame is held by stainless M3 bolts with hexagonal heads in the hope that this gives a little bit of realism. The design is pretty basic - lots of right angles and M3 is of course not scale - but there's no way I will tap all these threads in M2 ;)

Drive is through four RB35 motors. Wheels and tires are from the Traxxas Slash 4x4 and offer a small rim diameter on the outside, but a large one on the inside, allowing more room. Initially I had planned 6x6, but couldn't do driven front wheels with wheel-lean and so went for non-driven front wheels with wheel lean.
I plan to cover the rims eventually as it looks too much like a sports car, but I am not quite sure how to do that - yet.

All functions are operated by electric motors, either in servos or as gear motors. I opted for the cheap MG995 servos. Their performance issues are not so much an problem for a slow machine as they are for airplanes. But the looseness in the gears is problematic. The 996R is much better, I hear. Might upgrade eventually.

I converted one servo to a spindle drive (to tilt the moldboard) and used a gear motor with a pinion-pinion transmission to move the moldboard sideways: The driven pinion has an M4 thread tapped into it and drives the brass M4 threaded rod. Works nicely and seems robust enough to cope with dirt - but this is clearly not ideal, so I will have to think about some kind of shielding.

http://farm6.static.flickr.com/5068/5664881070_701bc13f79.jpg
http://www.flickr.com/photos/22070130@N07/sets/72157626598857828/

The three servos controlling the drawbar position are operated through "hydraulic modules". These make the stick position proportional to the servos' speed, not their angle.

All in all, the following functions are integrated:

drive (RB35 ESC)
steer (servo)
wheel lean (servo)
articulation (modified servo, continuous rotation with secondary gear drive)
moldboard angle (modified servo, continuous rotation with spindle drive)
moldboard sideshift (gear motor with spindle drive)
drawbar left height (servo, hydraulic module)
drawbar right height (servo, hydraulic module)
drawbar horizontal position (servo, hydraulic module)
rotation of these three servos around the centre axis (gear motor with hollow gear)
circle rotation (gear motor with worm drive, infinite rotation of circle through four-pole stereo plug)
front blade (servo arm is lever)
rear scarifier (servo arm is lever)

That's 13 functions, and assorted cables...

http://farm6.static.flickr.com/5264/5664879730_e0421cbdd7.jpg
http://www.flickr.com/photos/22070130@N07/sets/72157626598857828/

Everything is controlled via two modified Turnigy 9x 2.4GHz transmitters, these are 7.5 channel transmitters. This means I have one proportional and two on-off channels left). Currently I run the standard software, but calibrated the custom sticks I use. They started their existence as Cyborg V.1 flightsticks for flight simulators. Added onto those are Playstation thumbsticks, partly modified to give friction (non-returning) operation.

http://farm6.static.flickr.com/5096/5526362522_22892647a1.jpg
http://www.flickr.com/photos/22070130@N07/sets/72157626598857828/

Also modified are the two remaining sticks of the original transmitter. Their vertical axes are the only ones left operational - one has been modified with parts from the other transmitter to give friction operation. This allows easy operation of the two attachments. Driving the machine happens with the left flightstick, so the right hand is free to operate the attachments.

http://farm6.static.flickr.com/5227/5664879276_a6f1560319.jpg
http://www.flickr.com/photos/22070130@N07/sets/72157626598857828/

The Bruder model is a slightly older model, but I went for the new user interface of the M-series, hence the crossbreed of flightsticks with thumbsticks ;) This comes closest to the original user interface, without the use of foot pedals or advanced electronics. Here's a video of the real deal:

http://www.youtube.com/watch?v=2NkATUsfK7Y

As it's pretty much done, apart from improving some areas, I cannot provide the joy of a build thread, but if you have any questions, I would be very happy to answer your questions - we need more graders on the parcours :)

Best wishes
Jens

[Iron Art]

JensR, With the tools you used and the skill that you put your grader together, Well Done!! Welcome. Fred

[RCTech9]

WOW Im Speechless!!!

[mototodo]

:eek:

[TheMachinist]

Way cool! I lover the great improvising of parts. The ripper mechanism is really slick:cool:

[fuzzy]

great build with simple tools.

[kerst]

Great engineering!

Kerst

[Lil Giants]

Quite the Frankenstein! :eek:

But that is just unbelievable engineering of the radio gear/joysticks! :cool:

Looking forward to seeing the upcoming videos of it in motion. :)

[rc_farmer]

:eek: I have to second the afore mentioned comments. You have some serious electronic skills there!

[SmallHaul]

Cool machine! looks like a blast to operate.

[doodlebug]

Hey Jens, welcome to the forum, You've made a big impression already!
Looking forward to seeing more of your project's!
Later, Neil#2 aka doodlebug.

[JensR]

Wow, thanks very much folks :)

> Quite the Frankenstein!

#hahahaha#
Yes, I have sourced bits and pieces from "everywhere". Lots of modified parts from R/C cars (Tamiya, HPI, Traxxas) or circuit-board accessories (spacers and these threaded "stands") and lots of parts from Conrad and some from robotic companies as well as DIY stores.

Glad you liked the ripper/scarifier, The Machinist. I changed the design slightly for the front.
http://farm6.static.flickr.com/5110/5664880862_54cd1f8231.jpg
It is a bit more sturdy, but wouldn't easily fit on the rear.
The monstrosity that is the lever is rather terrible, in either case:
http://farm6.static.flickr.com/5143/5664877298_466c05abe4.jpg
I was thinking of using a low profile servo and sinking it into the 30mm square tube so that only the servo arm sticks out. But these are rated at only half the torque of the full size servo and I am not sure whether I should give it a try.

As to the controls: They work great - but I am still learning them. It's not easy to control so many functions. Also I had to set up my transmitters properly so that the controls aren't too twitchy. If you let the servos run at full speed, even a slight twist of the stick will completely change the position.
I also added a mixer so that leaning the front wheels still leaves them pointing forwards.

BTW, I don't think I'm skilled with electronics - all of this is simple electrics only: Cut the wires to the transmitters' potentiometers, crimp on servo plugs (tedious, but easy), extend cables to joysticks' potentiometers which also get a crimped servo plug and you are done.

I've already done a few videos. But they are all pretty bad and flickr's compression does not help.

Test in corridor, with improvised controls:
http://www.flickr.com/photos/22070130@N07/5190391463

55 seconds of grading:
http://www.flickr.com/photos/22070130@N07/5524641557

This one is sped-up, showing what I did to the beach ;)
http://www.flickr.com/photos/22070130@N07/5525285576/

Cheers
Jens

[grumpygrady]

very nice i really like it
i like that you built it with what you had or could get
i think that some folks forget that this hobby started out with what you could build as there was nothing for sale any where
please post more of your equipment and your other RC's
thanks again for posting

[JensR]

Thanks! :)

I have the utmost respect for people using advanced tools, but there are still plenty of models to be built and fun to be had with simple tools and what we used to call "kitbashing".

Thanks very much for your interested in further models, but I don't really have anything else to show.
Two crawlers and an unfinished crawler as well as some flat-surface racers. Not even good as a load on a truck...

[modelman]

JensR-sorry for the mis-name.:o I do know the difference between a grader and a scraper. Have you had your model in the dirt yet?

[JensR]

No worries ;)

Yes, once in sand at the beach and twice in compost.
Works very well, but controlling it is a real challenge.

Must get myself a youtube account, uploads to flickr are rather low quality, I assume due to recompression(?), plus I need to cut my videos together.
You can find some basic videos from my first test drive at the link above.

So, here's my first Youtube video...
http://www.youtube.com/watch?v=SZS9mkeum5I

I'll have to learn to edit videos, I guess.

Cheers
Jens

[JensR]

I folks!

I thought an update would be in order :)

Youtube videos here:
http://www.youtube.com/user/YensR
Also shows my Arduino-based project to make a transmitter myself.

Build pictures here:
http://flickr.com/gp/22070130@N07/13BERN

Lots of small things amounting to some progress:

Needed to crossdrill the wormwheel to prevent it from slipping.

Crossdrilled the motor shafts to install 2mm pins and standard 12mm hexes,
as the old grub-screw hexes proved unreliable.
Then tapped the motor shafts (internal M3) to mount the wheels, as the old fixture
with a grub screw collar was really bad.
http://farm7.static.flickr.com/6083/6137680699_44853179e4.jpg

Modified the Slash wheels:
http://farm7.static.flickr.com/6157/6137680597_1d7a66a17f.jpg

Modified the front and especially the rear implement mechanism:
http://farm7.static.flickr.com/6152/6138227048_761e2b3351.jpg

Modified the hood/bonnet
http://farm7.static.flickr.com/6082/6137681483_a55d69889e.jpg

Added mechanical floating positions for both circle lifts:
http://farm6.static.flickr.com/5183/5882615373_3b78d015cf.jpg
complete with new switches on my joysticks
http://farm7.static.flickr.com/6162/6137680277_8e300df577.jpg
(The red switch is the dual rate, which gives me two driving speeds.)

Improved the articulation joint with thrust bearings

Currently I am working to get my driven front axle going, it's looking promising:
http://farm7.static.flickr.com/6120/6221570069_b70b25eb95.jpg

Cheers
Jens

[Espeefan]

Wow! Very impressive! I always like seeing what people can create with the most basic of hand tools. You've done a great job, with the bare mininum, and you should be very proud. It might not be 100% scale, but it runs like it's supposed to!

The joystick control is equally amazing. I can see you have some great electrical abilities!

[Lil Giants]

Timelapse video was way too fast!!! Can you cut the speed of the vid in half or more plz? :confused: I'd like to see you work the controls. :)

[JensR]

Thanks guys!

The timelapse videos are of course only intended to give an idea how the terrain is changed by the grader.

I uploaded two new videos.
Here's the control of the grader:
http://www.youtube.com/watch?v=Kz77vpSWsjk

And here's the driven front axle with wheel lean.
http://www.youtube.com/watch?v=VjHcA7xACFU

I think this is the first model of a motor grader that combines 6x6 and wheel lean :)
I wanted to do this straight from the start, but did not find motors short enough.
Took quite a bit of CAD to get the dimensions right - plus my jigsaw complained about the 10mm aluminium...
Looking forward to giving this a whirl in the dirt!

Cheers
Jens

[FreddyGearDrive]

Wow! Now this is slick!:eek: I'm totally blown away with the radio configuration! But then again, The whole machine is SWEET!
Nice job!
FGD

[JensR]

Thanks again :)

I was at the beach, testing the new driven front axle - works very well.
But then the steering servo stopped working. It came back to life for a few seconds later. Not sure what happened.
I finished the day steering with just the articulation.

Back home I managed to squeeze in a standard-size servo.

I made a video, too.
http://www.youtube.com/watch?v=pjL3S6gX6h0

Not as good as some of the stuff I see around here, but hopefully still fun to watch.

Best wishes
Jens

[Lil Giants]

That's fun to watch! You're becoming quite the pro at operating it. :cool:

Can you dial in EPA for your throttle ch? Just a thought, maybe cut the forward max to 50% so it doesn't lurch while you're blading... maybe less.

That last 15secs, that was a great viewing angle, do you have some one helping you film? Be great to see more footage from that view. ;)

[JensR]

Thanks :)

You are right about the lurching.
I did have Dual/Rate programmed. (That's the red button in my earlier video of the controls.)
However, for whatever reason, I cannot get the ESC to behave. This means if I get proper D/R in forward, I hardly get any speed in reverse.
Not sure what is happening here. So I disabled it for the moment.

For realism, the steering speed is also too high. I cannot change this on my current radio, though. Might put it in one of those Turnigy servo-delays.

The viewing angle as the end is done by me - I'm sitting on the ground and driving the grader with my left and aiming (more or less) the camera with my right.

Cheers
Jens

[hauler_10-4]

WOW ;)

[rc_farmer]

Glad to see you grading some sand, its very impressive.

[rc_farmer]

Thanks :)

You are right about the lurching.
I did have Dual/Rate programmed. (That's the red button in my earlier video of the controls.)
However, for whatever reason, I cannot get the ESC to behave. This means if I get proper D/R in forward, I hardly get any speed in reverse.
Not sure what is happening here. So I disabled it for the moment.

For realism, the steering speed is also to high. I cannot change this on my current radio, though. Might put it in one of those Turnigy servo-delays.

The viewing angle as the end is done by me - I'm sitting on the ground and driving the grader with my left and and aiming (more or less) the camera with my right.

Cheers
Jens

Help me to understand why you chose to use D/R for fwd/rev or am i misunderstanding whats happening.

[JensR]

Thanks guys :)

D/R on the forward/reverse gives you a much finer-grained control on the stick.

With D/R the full stick movement means only half (or so) of the speed, so it makes finely-controlled driving easier.
This obviously requires motors that are strong enough with the lower voltages. But if you have that, it's almost like a second gear. Well. Almost.

I hope it's just a setting problem and I can get it back to work and maybe even get it to work better than before.

Hope this makes sense?

Cheers
Jens

[JensR]

Wow, cannot believe it's been another year!

In the meantime I have done a lot of things and still need to do some more.
Given it's my first project of this size, I don't mind, but I really want to get it done - but not rush it too much, either.

I have painted the machine and as it's my design, I decided to go with my "corporate" colours ;)
I made a larger mouldboard and did a better, more dirt-resistant mouldboard side-shift, including a rubber skirting to prevent dirt to fall onto the .
The front blade was increased in size, the ripper servo-saver stiffened up.
The floating mechanism for the circle lift was improved - less drain on the servos, better clamping force.
Circle sideshift was converted from servo to M6 threaded spindle.
Articulation is controlled by a sail servo now, allowing comfortable steering modes.
Improving the saddle rotation is my biggest worry currently. The sail servo does not cooperate with my "hydraulic module" (makes servo speed proportional to stick position, as opposed to servo position proportional to stick position). I know the real machines do not have an active drive on it. Rather they use the main cylinders to force the saddle to rotate. I might have to do that, or will have to look into other alternatives.
I also put a lot of weight into the machine, now at 9.6kg and therefore still slightly lighter than a 16M would be in 1:14.5, but it has helped with traction a lot, especially as the machine is 6x6 (which the 16M doesn't offer ;) ).
The circle drive was improved by having a proper worm&wheel and not mis-using a worm on a regular gear.
I also managed to improve the geometry/kinematics of the whole thing so that I can lift the mouldboard a bit higher.
And lastly, I installed some lights :)

Here's the collection of images going to through the building stages

http://flickr.com/gp/22070130@N07/13BERN


and here are a few selected ones showing the "recent" stage:

http://farm9.staticflickr.com/8002/7505298820_3b3354884e_z.jpg


http://farm8.staticflickr.com/7273/7578549466_e2e12c2685_z.jpg
from
http://www.flickr.com/photos/22070130@N07/7578549466/in/set-72157626598857828

http://farm9.staticflickr.com/8462/8038027471_1f40f7486a_z.jpg

http://farm9.staticflickr.com/8037/7990392962_d0f30df65a_z.jpg

Cheers
Jens

[dabears]

Looks Awesome!!! Very cool!

[doodlebug]

I like the color scheme! nice progress.

Cheer's, Neil.

[Hemi1966]

Jens, I really like the color. It's nice to see something else than yellow:)

[Stefan]

Looking great, Jens. Very cool! At some distance you hardly notice it´s not 100% scale. Especially when the lights are on.

Stefan

[Dieselchopper]

Very cool good job.

[JensR]

Thanks everybody! Much appreciated :)

Did a bit more detail work, painted the new blade and rotation mechanism, installed a better ESC and just these last two weeks built and installed a new better floating mechanism.

Managed to shoot a bit of video, again, not very high quality:
https://www.youtube.com/watch?v=_nXoehdzEL0

Updated pics at the usual location:
http://flickr.com/gp/22070130@N07/13BERN

[Espeefan]

Great updates! Glad to see this machine is still alive and kicking, with some improvements to make it better. I do like the fresh paint and working lights. From the right angle it looks nice and realistic.

[rc_farmer]

Very well done.....:D

[JensR]

Thanks folks! :) :)

Has it really been over a year again?!
Looking at the photos, it seems hardly anything has changed!

http://flickr.com/gp/22070130@N07/13BERN

But behind the scenes, I did a lot of time-consuming improvements on the floating mechanism, serviceability and reliability of the mouldboard sideshift and have converted the saddle-drive with a saddle-clamp, similar to what the 1:1 graders have. The torque generated from the forces on the mouldboard to the variety of gear motors I had used before was just too high. I still think a motorised saddle would be neat, but it would require quite a bit of re-engineering, fitting a larger gear motor and most importantly a sturdy worm drive...

Recent (and ongoing) improvements include converting the front motors to brushless motors with considerably more power. That's done now, but I need to hide the dual ESCs and extra wires inside the frame.

For the next year or so I have a few improvements planned for the main drive as well, plus a whole list of electronic features. All of these will be tested on a wooden mock-up - if they work, I'll transfer them to the real machine.

This will allow me to use the grader while I work on those gadgets. I've been out driving a few times over the last weeks and have done a few youtube videos, which you can see on my youtube channel

https://www.youtube.com/user/YensR/videos

Hope you enjoy these!

Best wishes
Jens