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mike_o

6WD 6x6 WR-01 / Wild Dagger project

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I have a few WR-01 gearboxes left over, and I decided to launch a 3 motor/gearbox snowmobile project. It will have narrow trackwitdth (TL-01 suspension arms and dogbones), but use 70mm wide, 135mm diameter V-pattern wheels. Steering of front and real wheels, but not the center pair. Wheel-set base identical. Overall wheelbase close to the Wild Dagger. I'll probably use 28x22mm low-KV outrunners to provide steering movement space for the big wheels. Also outrunners will lower RF noise level for better FPV usage.

Did anybody do something like this with the WR-01 gearbox before? (I did a search, but didn't find any)

And the $10.000 question: What body to fit on such a Frankenchassis??? The center wheel pair will make most ordinary bodies look out of place...

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post-34574-0-46886600-1451474602_thumb.j

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How about using a lorry cab up front, with a flatbed or box rear section? Lorries come in all sorts of configurations and wouldn't be completely unrealistic if matched to the proposed underpinnings.

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I saw a 6x6 blackfoot on ebay just before xmas, nearly posted a link but I was almost contemplating snaffling it myself!

I can't remember the steering setup. Would you not consider all three axles steering, like real trucks that have both sets of rear wheels turn. Would it not upset the steering in if the centre wheels don't turn but rears do? I guess you don't know until you try.

Good luck with it, sounds a real fun project. I was thinking maybe a hilux front cab and chop up two rear bed sections to accomodate the two rear axles, I'd personally extend the wheel base of the standard WR too to keep it all in proportion with the concept.

I look forward to whatever you end up producing, big fan of this chassis and it's great to see it being pushed.

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Did anybody do something like this with the WR-01 gearbox before? (I did a search, but didn't find any)

I made this a few years back, but shelved it due to lack of funds

6x6-1.JPG

6x6-2.JPG

6x6-3.JPG

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Thanks for the inputs, and to Twinset for sharing his nice build, which does raise the bar a bit too much ;). My previous WR-01 builds have been a bit less sophisticated, albeit still fun to run.

image.jpg1_zpshcmjbsyb.jpg

Since my center wheels will be in the, erm, center, the Mercedes type chassis will not work. But I'll have a look at the lorry cab idea. I probably need to build up the chassis to see how the steering servos, big wheels, and short suspension arms go hand in hand before finally deciding on the body

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Love the swb one above and what you've done with the track front/rear.

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I made this a few years back, but shelved it due to lack of funds

6x6-1.JPG

6x6-2.JPG

6x6-3.JPG

Stolly! 😜

For those not in the know... Alvis Stalwart amphibious military transport from the Cold War when it was expected NATO would be fighting across Europe and needing to ford many rivers.

16889742-1EB5-422F-8BD7-8209E274A55C_zps

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I made this a few years back, but shelved it due to lack of funds

6x6-3.JPG

Hey Twinset.. what wheels and tires are those bigger ones off of?

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I have received the wheels, but as TWINSET points out, the usual #50736 TL-01B uprights doesn't work straight out of the box with these big wheels. I found that the TA-05 parts can do the job with a simple 2.5mm washer (picture), but Bazai hobby is VERY slow and somewhat unresponsive in getting my parts shipped, so the snow is long gone before my project starts rolling.

20160131_1357381_zpshroc0scm.jpg

Meanwhile, I'v tried out the wheel on another frankenchassis, and it came out a little tractor like. Runs great, although it certainly doesn't suffer from oversteer - unless you run it backwards :)

20160131_1420461_zpsnw0bvgvy.jpg

I also decided against my original idea with steering front and contra steering rear wheels, and will go for steering (100%) front wheels, steering (50%) middle wheels, and fixed rear wheels like the Alvis Stalwart. I think this will handle better at any speed above crawl...

These days, I rub all my vehicles brushless, but the idea of triple ESC scared me into getting 3 RS-365SH "silver cans". they are only 28mm (D) x 33mm (L) so they will leve clearence for the big wheels. Rated at 35watts, they are not powerhouses, but with 3 of them at a low gearing, it should work out anyway.

rs_365sh_1.gif

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Trying to keep it compact, but still making room for the B I G wheels to turn/steer. Mounted one of the 365 cans and lined it up next to a 540 silvercan.

20160202_213834_zpsq4ga6o2m.jpg

I'm hoping to use short swingarms, but even with the small motors, it may not be possible....

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As you see from the time since last post, my project hasn't moved much forward, and with the challenge of very little room for the big wheels to turn and little spare time in general, the build came to a stop. In anticipation of snow to come and with a little more time at hand, I have taken it up again and re-evaluated the turning issue.

What I have come up with is another idea: To build all three motor/gearbox/suspension assemblies identical with fixed (non steering) uprights and instead turn the entire assembly instead: Central fixed motor assembly with frame/battery/electronics/servos plus forward and rear motor/gearbox assemblies turning on a vertical shaft.

[frontmotorassy]---[central motor/frame assy]---[rear motorassy]

Clearly, this is no good for high speed turning, but the 6x6 is intended for snow-crawling, so it might work. Or what? Any inputs / ideas?

 

thanks

 

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Might I suggest you have a look at my skidder build:

which has an articulated chassis. From your above post I take it that you're thinking about a double articulated chassis.

My experience of my own skidder is as follows:

 

1. Articulated chassis can be very manoueverable and has an excellent turning circle. A double articulated chassis is likely to have even better turning performance, but it might be mechanically simpler to use a single hinge between the front and middle axles and  make a solid connection between the 2 rear axles.

2. You'll need a lot of power to operate the steering. I used a custom made system which was essentially a servo powered by a 540 motor.  I think you'd want at least 2 servos on each hinge to operate the steering, possibly even 2 1/4 scale servo for max power.

3. As you don't have to transmit drive power through the hinge as I did with my design, you can make the hinge move through more than +-40degrees, which could make for a fantastic turning circle, but the differing wheelbase on each side of the vehicle can make it unstable if you're trying to go sideways across a slope.

4. It's sometimes possible to wriggle the vehicle out of tight spot with the steering as the distance between the wheels changes on each side as the steering is operated (For example being able to drag a wheel out of a hole), which you can't do with conventional steering.

I say give it a go. Articulated steering chassis can be tricky, but it you want to use as a crawler I think you'll be happy with the results. You might also want to go the whole hog and build something similar to the chassis design of an 8x8 forestry forwarder (google them and have a look at some videos on youtube), which is basically 2 4x4 without steering attached through a articulated chassis steering hinge :)

 

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Madinventor,

 

thanks for the comments and the link. That is one intimidating build! I was hoping the reduce servo load by having the pivot point just over the axles, but I sense the challenge.

After fiddling a bit more with the suspension and the wheels (and looking at your build), I may even go back to the original idea of the Stolly / Stalwart configuration. Worst case, I'll have to change the wheels or at least swap the foam inserts for taller, more narrow ones.

 

Still no snow here, so I might make it this year :P

 

Happy New Year all! 

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I missed this thread first time around but it seems like a really cool concept.

If I was doing this I'd be sticking with conventional steering and having the rear axles located together at the back and the front axle further out front, like a conventional 6x6 tractor truck.  For better handling at low speed I'd have steering on the rear axle but at a reduced throw, as the rear wheels won't need to turn as tight if it's pivoting around the middle wheels.  With a Spektrum handset you have an option to disable steering on the rear axle, so it could be more stable at speed.

But I'd do it that way purely for aesthetic reasons, because that's how I like my trucks to look.

I'm not sure an articulated chassis will work too well with a 6x6 design if the axles are equidistant from one another.  If you have a single central pivot, the middle axle will try to move laterally when you turn and at low speeds that might put far too much load on the servo.  Even you have two pivots, mounted half-way between each axle, you'll still have some lateral movement.  The closer you move the pivots to the front/rear axles, the less lateral movement you'll get.  I'm not good enough at geometry to work out exactly how much lateral movement you'll get but there's probably a simple way to work it out.

If you pivot the front and rear axles rather than the chassis, you have no lateral movement in the middle of the chassis.  However when stationary your left and right wheels will run in opposite directions, so you'll drag the tyres at low speeds if you have locked diffs - but with 3 independent gearboxes you might find traction is good enough without needing to lock the diffs.

I was wondering if you could rotate the gearboxes through 90 degrees to get more space (they're a bit cumbersome for this application, IMO) then you'd lose the independent suspension and you'd have to hang them on suspension like a Clod gearbox, which would be even more cumbersome!

Will watch with interest :)

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Edited: The one ESC for several, sync'ed brushed motors didn't work in real life. I tried on the desk several times, and I think it would work on a plane, but I beleive that the mechanical coupling (via the ground) between the motors prevents them from sync'ing up nicely.

I just made an interesting discovery today: I have always assumed that you could not run more than one (non-sensored) brushless motor on one ESC due to the specific timing and EMF feedback circuit. But it is actually possible, and you even get the benefit that the two motors will run perfectly syncronised. To see for myself, I hooked up a pair of NTM 3836mm 910kv motors on a single 18A ESC and switched it on. The ran just flawlessly and the ESC didn't seem to suffer.

It turns out that the motors actually help each other to stay in sync; If one looses out, the slight timing advance of the other will transfer energy to the other, thus helping the ESC. Of course the ESC rating has to follow the sum of the motor ratings, and there is some losses under certain loads that will increase, but this basically very good news for owners of the Twin Motor series (Wild Dagger, Twin Detonator, etc) and for my 6x6 project.

I was worried about the mechanical stability, gear / ratio selection, and power output of my 365 size brushed motors, but now it all goes away. I've purchased an extra NTM 3536 motor and three 4mm/3.17mm stepped shafts, so all the mentioned worries are gone. I did have to get an 80A ESC, but the waterproof version were on sale at HK, so it went into the cart along with the NTM and the shafts :)

 

Will post pictures when the build progresses.

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55 minutes ago, mike_o said:

I just made an interesting discovery today: I have always assumed that you could not run more than one (non-sensored) brushless motor on one ESC due to the specific timing and EMF feedback circuit. But it is actually possible, and you even get the benefit that the two motors will run perfectly syncronised. To see for myself, I hooked up a pair of NTM 3836mm 910kv motors on a single 18A ESC and switched it on. The ran just flawlessly and the ESC didn't seem to suffer.

It turns out that the motors actually help each other to stay in sync; If one looses out, the slight timing advance of the other will transfer energy to the other, thus helping the ESC. Of course the ESC rating has to follow the sum of the motor ratings, and there is some losses under certain loads that will increase, but this basically very good news for owners of the Twin Motor series (Wild Dagger, Twin Detonator, etc) and for my 6x6 project.

I was worried about the mechanical stability, gear / ratio selection, and power output of my 365 size brushed motors, but now it all goes away. I've purchased an extra NTM 3536 motor and three 4mm/3.17mm stepped shafts, so all the mentioned worries are gone. I did have to get an 80A ESC, but the waterproof version were on sale at HK, so it went into the cart along with the NTM and the shafts :)

 

Will post pictures when the build progresses.

Good to know. Did you swap one of the cables over to get one motor running backwards?

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Nobbi,

in my build, the gearboxes are oriented in the same direction, so the motors spins identically. But swapping two wires will make that motor run in the opposite direction. I did test that on a two motor set-up. 

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1 hour ago, mike_o said:

Nobbi,

in my build, the gearboxes are oriented in the same direction, so the motors spins identically. But swapping two wires will make that motor run in the opposite direction. I did test that on a two motor set-up. 

Might have to get a China cheapy to play with :-)

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I decided to skip the articulated chassis and go stolly-style. The chassis is almost done, missing servos, BL motor mounting and some track width adjustments, but I'd like to share a few pictures:

 

image.jpeg

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Failed upload on 2nd picture, am I only allowed a certain MB per day/thread/post???

image[1].jpeg

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Winter is forecast for next week, so I have accelerated the Stolly build. The platform is now running, albeit with small wheels (clearence problems with the 135mm ones) and small RS-365 Mabuchi brushed motors. Still it works very well, and I'm surprised how smooth it is.

 

 

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I've driven a bit more and I'm very pleased with the chassis. Need to use a thinner shock oil, as thing get a bit bumpy at speed. Also, I managed to break the stock servo saver spring ring. Fortunately, I got two more, as I got 3 packs of the plastic parts containing these. I use a smaller servo for the middle wheel, as they turn less ans has a lower gearing. This servo has no saver, though, as I reckoned the middle wheel are fairly protected...

 

Finally, I decided to go with the 130mm Wild Dagger spike tires/wheel. I have 4 new ones from above biuld, and I ordered a pair for the reamining axle.

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That looks great - good work!  What shocks are you using?  They seem to work well in the video.  Love to see that independent articulation.  In fact the whole thing looks better than I imagined it would, I might have to build a copycat project in the future :D

It actually reminds me of an idea I had for an amphibious RC some time ago - could be a good starting point ;)

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