Here’s an image of my concept. It’s basically one half of the chassis. My idea was to use a lightweight approach. I’m using a 5 amp motor on each wheel for a total of 20 amps maxx. A 540 style motor draws around 20 amps max, so it a power to weight ratio thing. Of course it’s still far from complete, but I had a few spare minutes last night so I started fiddling things together. Now I realize having the steering on the SES tube will be less effective as the tube becomes more horizontal. I’m still considering putting the steering servo on the motor and keeping it level with a dual arm setup. Anyway don’t be too critical as it’s just the first stage of what is sure to evolve as I go.
Oh I forgot to mention the beast will be controlled from a single SyRen 10 because it uses Ackerman style steering (sort of) we only need a single channel motor controller. You could even make it 4 wheel stering. The top of the chassis, the “U” channel, is the top of the vehicle. There’s no need to carry more than a LiPo battery, the SyRen 10 and the RC receiver. So it’s not going to be much larger than it currently is.
It’s an cool and interesting design! It reminds me of the chassis build with the GEARS educational set, where it has a pivot at the top of each wheel assembly that allows it to easily go over many obstacles.
That motor should give the rover some zip and power to spare. I have one of the Stinger motors, which I believe is a 540 size motor, a friend gave to me.
I think the dual arm setup would definitely work better in your design, with the steering servo at the motor.
It’s really cool how each of us can come up with a completely different design for a rover with suspension, and each design is very good. Now, we just have to build our respective rovers! You are way ahead on that, with your easy access to the entire toystore.
The motor is in the “hit me” path. I would rather see the motor mounted above the wheel, linked with indirect drive. That way the motor isn’t jutting out to be hit by rocks, etc.
The steering limitation, as you have mentioned. A parallelogram setup is much better. Not to mention easier to add shocks too!
On the single motor controller, do you have a way to wire the motors up so they draw different currents? I may be overengineering, but as you go around curves, motors on the outside of the curve will be doing more work then motors on the inside of the curve. Hence, the reason cars have differentials
Ok, but if you compare it to a traditional crawler wich has that annoying differential knob in the center of the axle it’s a step in the right direction. I also forgot to mention that I want to make a shorter hub to nest the motor more inside the wheel rim.
I know, but I don’t think there is any difference when adding shocks. It’s just a swing arm either way.
It’s the voltage that you control, not the current. But I hadn’t given it any thought as rock crawlers traditionally lock the diffs and do have difficulty turning. I will build it up hopefully this weekend, just to see how it performs. It’s fun anyway.
That’s incorrect. Real rock crawlers (and my scale one) can disconnect the rear drive and turn very sharply, sharper than even 4-wheel steering using 2 servos. Obviously a differentially steered vehicle can turn in place, and my design uses diff steering.
Larger diameter wheels are the best way to get more ground clearance. Your design looks like it’s going to tip over very easily on rough terrain. I’ve seen plenty of crawlers with a too-high COG suffer this problem.
I admit that my interest in this is new and I don’t know everything. I got the impression that they routinely lock the difs by reading many modification sites where the purpose was to convert an RC MT to rock crawling. Obvoiusly real crawlers can lock and unlock the difs.
They do always lock the diffs. I wasn’t referring to unlocking the diffs. Many real crawlers actually disconnect the rear drive axle from the transmission to turn sharply. Hope that explanation makes more sense.
The crawler is posed in it’s highest position. The shocks aren’t even installed, so it’s a little early to tell if it’s top heavy at this stage. Jeeesh I said don’t be too critical as it’s early in the design process.
Nested would be better then exposed, but I still think a ‘brush guard’ of some sort is needed. The motors of the crawlers I am familiar with are all protected, only exposing a cheap diff. It would be cheaper to replace a SES component rather then a gearhead motor.
And sorry for being so critical already, despite you telling us not too! friendly hug
That makes no sense whatsoever. In order to turn sharper then a 4 wheel steering vehicle, (with fixed axles, so not skid steering,) it seems to me that the entire axle assembly has to be on a pivot. To me, that seems stupid as it would sacrifice a lot of structural integrity. Otherwise, how do you turn sharper then a 4 wheel steering vehicle?
(I am of course assuming that differentials are used, as they should be in all fixed axle vehicles, and that the diffs are not locked to cause undo friction)
I know I know, I was trying to keep the weight to an absolute minimum and direct connect was the way. I know it’s a weak lnk. I did have fun sanding the hub-08 so it could mount to the HMSH-01.
I’m not really sure what you are trying to say either. A 4WD vehicle with the rear drive disconnected is just a front wheel drive vehicle. I don’t see how it can turn with a tighter radius than a 4 wheel steer vehicle…
It does. My buddy’s crawler is 4-wheel steering, and mine has a disconnect. They are both the same size, and mine turns sharper. I’d like to post a video, but prolly won’t be able to. Sorry, not sure what else to say. This is well-understood among the rock crawler crowd.
Edit: Ok, maybe I can attempt to elaborate. When I say it turns sharper, I mean a smaller radius. Keep in mind these vehicles can’t turn unless they move forward (unlike a diff-steered bot). I probably should have mentioned that in addition to disconnecting, it also locks the rear drive shaft so that the rear wheels can’t rotate. Mine just drags the rear wheels around in a tight circle. Better?
This is interesting… I think it’s a possibility to check out… It needs development, but if we stay with always the same things, we eon’t advance. I’d likle to see it full with srpings, it would be nice.
I still don’t believe you. I just built a vehicle from lego that has the option of being either a 4 wheel steer, or a front wheel steer. It has diffs on both front and rear axles, and a solid shaft connecting front and rear axles.
In Front Wheel Steer only mode, it turns completely inside a circle with a 18.5" diameter.
In Four Wheel Steer mode, it turns completely inside a circle with a 15" diameter.
I really don’t know what to say, but based on the little empirical data I just got, I would have to say that four wheel steering is the way to go.
