Today, I had to charge my LiPo battery for the first time since I bought the equipment for the OpenRC car about a year ago or so.
This thing is crazy fast with the metal drive train!!! (Not that I have anything to compare it to…)
One thing I have notice, the wheels seem to want to collapse in on the back end. When I push down on the frame, the wheels are straight up and down. Do you think the turnbuckle needs to be longer to prevent this?
For the wheels to stay vertical, the top and bottom links need to be the same length and parallel. Also, you don’t want the mechanism to travel to a place where slop in the linkage lets you get near a toggle (over-center) position. Look up four bar linkages for things that can happen. In the case of vehicular suspension, there is probably a performance reason to not have the wheels always upright with regard to the chassis, or it may be a design compromise. In other words, I’m not sure it’s a problem, since you shouldn’t be spending any significant time at full extension.
I’m not sure it’s a problem to be solved. This geometry should be designed so that tire grip is maximized. That usually means the tires are vertical with the suspension neutral or squatting slightly under acceleration, and tipped in a bit at the top when compressed (as when the chassis rolls during cornering). Deflection of the tire will complicate all of that, and it’s all very difficult to predict.
I’m not familiar with all of the geometry of the truggy, so I can’t tell you what link should be longer or shorter. If it isn’t handling the way you want, then you’ll need to study it in motion to see how the tread meets the ground. From there, experimentation will reveal what works best. Different links, different tread, or maybe different geometry of the tire carcass.
Hey Brandon, making the camber link longer will actually give you positive camber, which is bad! In the 20 years I’ve been racing off-road rc cars we have always ran between -1° and -2° camber. This has the top of the wheels pointed inwards slightly.
To set this length properly with adjustable turnbuckles, you’ll have to first set ride height. A good rule of thumb for this is to start with the dog bones level in the rear of the car. You do this will a fully weighted car (meaning battery and all commoners installed you’ll be running) and by adjusting the shock collars. Once the rear is done do the same for the front, but this time adjust the shock collars to level out the chassis.
Now that you’re at a proper ride height you can use a camber gauge to help you adjust the camber link length. It’s pretty easy, just set the gauge to the desired setting (-1° is a good place to start) and push down on the car and let go before the chassis contacts the table. This settles your car into proper ride height position. Now place the camber gauge on the table and move it next to the outside face of the tire. Then adjust the length of the camber link till it matches the gauge. You’ll have to reset your vehicles ride height often during this and should even be done during ride height setup.
There are two types of foams! Open cell, which are the standard white foams and closed cell. Open cell is very soft and will easily compress, especially if there is extra area in the tire/rim cavity. Closed cell foams are more rigid and will not easily compress. However, they also require a specific tire/rim cavity to function properly.
In my experience, rims take too much abuse to print them from standard materials (abs and pla). It’s no fun gluing up a set of ties only to have a rim break on you! I mean you could bake the tire off the rim, but it usually kills the foams and alters the tire compound.
Hi Brandon, apart from the motor continuously coming loose I am running a stable mechanical car design now (with all metal drive). I would strongly suggest changing the steering stabilizer as Daniels original design i’m afraid is just not up to the job. I can point you in the direction of a better stabilizer if you wish and it doesn’t impact on the design (in terms of changes) you just need a longer m3 countersunk head screw and m3 nut to go with it.
@bcrazycramer where was the post from bitfrost about the steering components, would love to see that, haven’t tried to handle that part of the remix yet
I actually got to take it out for a test drive today! I ended up getting wild with it and one of the tires fell off and I rolled it. I broke the shock holder thingy and turnbuckle. I’m not sure if I’m supposed to glue the tire on the rim or not?
I’m still not happy with the way the tires set. I think I might try printing longer turnbuckles to see if that helps.
I need to get some M4 screws to hold hold the front piece that holds the wishbone to the frame. That pulled itself out and caused the wishbone to come loose and break the parts I mentioned above.
I had a good time racing it around for about 5-10 minutes. That’s a first for me!!!
@bcrazycramer you were using the steering components from the remix correct, not the original model? i tried to get the original one working with the remixed diffs and it was hitting it, still trying to get mine assembled
@bcrazycramer Did you end up solving this, mine is the same is yours. i also have an issue with the axles coming out of the rear differential when driving they aren’t in the metal couplings by much. This thing is crazy fast when it can run
