Bravin Neff
12-07-2002, 12:40 PM
Great little car!! Pretty quick, and the engineering involved is mostly sound. Here are some initial observations and criticisms, to aid in improving it:
1. Changing the front caster causes a tiny interference between the front knuckle and the lower front a-arm. This is minor, and could easily be modified for the proper clearance. I noticed this interference only occured on one of the arms, not on the other, and is just the result of tiny tolerances stacking.
2. Changing the front caster causes the steering arm to be a little out of wack with the steering servo. The stock position works fine, but in the alternate caster setup, it is not as effective.
3. In my opinion, the steering setup is the weakest design of this car, and it would be cool to devise some kind of tiny turnbuckle/ball-cup arrangement, though the parts would have to be so small it is hard to imagine finding the appropriate parts that would actually work. The stock steering does work well, though, and it tracks neutrally. The steering is quick and accurate. And the straight steering connector arm has enough flexibilty so as to appear to cause no interference with the front suspension's ability to work.
4. The diff-units on my car have a noticable amount of out-of-concentricity, or "run-out," between the outdrives and the spur gear. Consequently, since the outdrives are immobile, hard-located between their bearings, the spur gear will not spin a perfectly circular path, but will follow an eccentric and elliptical path instead. Fortunately the gear mesh has enough clearance to all but compensate for this. Technically, all gears have a degree of this, and can be ignored if sufficiently small. With these diffs, it is visually noticeable. The real reason I care about this on this car: you need to be able to turn one wheel, watching the opposite spin backwards, in order to adjust the diff. Usually this works fine, but if you do this when the spur gear's eccentricity catches itself on the high spot of it's rotation, the friction becomes too great and will catch causing the opposite wheel to turn WITH the wheel you are turning, and you will cause the motor to spin instead. It causes me to wonder how effective the diffs can be, as this run-out is tantamount to making the diff alternate between soft-stiff-soft-stiff during its rotational motion. I have NOT disassembled the diff yet, so it may just be a case where the parts need to be realigned. At any rate, for a car so small, I realize I am nitpicking here. Really, it's splitting hairs, and it appears to have no obvious effect on the car's performance when I drive it. The diffs do work as advertised, and I am amazed a car of this size has ball diffs at all.
5. Part fitment. I was amazed at how well most of the tiny parts fit together. I was expecting more slop, particularly between the a-arms and their tiny hinge pins. If you are familiar with how injection molding works, you know that it is not perfect, and no where close to a competent machining process. On my car, the clearance between the hinge-holes in the a-arms, the holes in the chassis, and the hinge pins seems to be as good as one could reasonably desire. If you could enlarge this car to, say, 1/10th or 1/8th scale, the fitment here would probably be better than any other car out there.
6. On the other hand, the clearance between the uprights and the wheel bearings is too great, as is the clearance between the axles and the bearings. It causes an unnecessary amount of slop in the parts. This seems to be something that would be easy to improve.
7. The stock suspension springs are too stiff, as I suspected by reading other's comments. I bought the optional spring set and installed the softest ones. They work well, and seem to provide a good load ratio to the car's weight. I ran the car on my shaggy carpet, and it has creases in it large enough that would normally cause a car this small to bounce around. The suspension soaks the bumps fine. This tiny suspension really is quite effective. But do put the soft springs in.
***
Please do not take my comments as disparaging. My aim only is to draw attention to the car's potential shortcomings, in the interest of improving the car, or helping others, or having someone prove me wrong and help ME understand better. This car is fantastic, really, and it causes one to wish it were perfect, given the fact so much engineering was devoted to such a small car. I would have killed for something like this when I was a kid, and it's still very cool as an adult. Now on to some questions I have for everyone...
1. I could not get the esc to setup properly, and I tried dozens of times. The directions claim that, after the red light stays on and the green light goes out, to pull the trigger all the way full-throttle until the green goes on and the red goes off. Then move the throttle full reverse until the motor beginss spinning in reverse. This never worked for me, and the car only seemed to run well after I turned it off and just turned it back on, without attempting to set it up. Even then, reverse never really works well (full forward works fine, but it just sputters in reverse, and very slowly). I tried every combination of throttle-channel reversing, messing with the throttle trim, and so on. I am suspecting that the radio I'm using (I'm using an AM airtronics blazer temporarily) is just not compatible with the receiver, as I notice people are having good luck with Futaba's and those Perfex ones that come with mini-z's. What do you all think? Is the red light supposed to come on during full forward throttle, which mine does, or is the green supposed to, as I would have expected? Perhaps the esc is accidentally wired backwards to the motor (I can't tell, since the motor doesn't have any marks to distinguish between + and -)?
2. After 3 batteries, I burnt out the motor. I noticed it got very hot, but just ignored it as nobody seemed to have any problem with this. There is an enormous amount of clearance between the long side of the armature and the motor's bushing, but I figured this was just sound engineering as the motor easily could bind if the alignment was not perfect (which it can't be, given the fact the shaft is so long). What do you all think about this?
Thanks for your time,
Bravin Neff
1. Changing the front caster causes a tiny interference between the front knuckle and the lower front a-arm. This is minor, and could easily be modified for the proper clearance. I noticed this interference only occured on one of the arms, not on the other, and is just the result of tiny tolerances stacking.
2. Changing the front caster causes the steering arm to be a little out of wack with the steering servo. The stock position works fine, but in the alternate caster setup, it is not as effective.
3. In my opinion, the steering setup is the weakest design of this car, and it would be cool to devise some kind of tiny turnbuckle/ball-cup arrangement, though the parts would have to be so small it is hard to imagine finding the appropriate parts that would actually work. The stock steering does work well, though, and it tracks neutrally. The steering is quick and accurate. And the straight steering connector arm has enough flexibilty so as to appear to cause no interference with the front suspension's ability to work.
4. The diff-units on my car have a noticable amount of out-of-concentricity, or "run-out," between the outdrives and the spur gear. Consequently, since the outdrives are immobile, hard-located between their bearings, the spur gear will not spin a perfectly circular path, but will follow an eccentric and elliptical path instead. Fortunately the gear mesh has enough clearance to all but compensate for this. Technically, all gears have a degree of this, and can be ignored if sufficiently small. With these diffs, it is visually noticeable. The real reason I care about this on this car: you need to be able to turn one wheel, watching the opposite spin backwards, in order to adjust the diff. Usually this works fine, but if you do this when the spur gear's eccentricity catches itself on the high spot of it's rotation, the friction becomes too great and will catch causing the opposite wheel to turn WITH the wheel you are turning, and you will cause the motor to spin instead. It causes me to wonder how effective the diffs can be, as this run-out is tantamount to making the diff alternate between soft-stiff-soft-stiff during its rotational motion. I have NOT disassembled the diff yet, so it may just be a case where the parts need to be realigned. At any rate, for a car so small, I realize I am nitpicking here. Really, it's splitting hairs, and it appears to have no obvious effect on the car's performance when I drive it. The diffs do work as advertised, and I am amazed a car of this size has ball diffs at all.
5. Part fitment. I was amazed at how well most of the tiny parts fit together. I was expecting more slop, particularly between the a-arms and their tiny hinge pins. If you are familiar with how injection molding works, you know that it is not perfect, and no where close to a competent machining process. On my car, the clearance between the hinge-holes in the a-arms, the holes in the chassis, and the hinge pins seems to be as good as one could reasonably desire. If you could enlarge this car to, say, 1/10th or 1/8th scale, the fitment here would probably be better than any other car out there.
6. On the other hand, the clearance between the uprights and the wheel bearings is too great, as is the clearance between the axles and the bearings. It causes an unnecessary amount of slop in the parts. This seems to be something that would be easy to improve.
7. The stock suspension springs are too stiff, as I suspected by reading other's comments. I bought the optional spring set and installed the softest ones. They work well, and seem to provide a good load ratio to the car's weight. I ran the car on my shaggy carpet, and it has creases in it large enough that would normally cause a car this small to bounce around. The suspension soaks the bumps fine. This tiny suspension really is quite effective. But do put the soft springs in.
***
Please do not take my comments as disparaging. My aim only is to draw attention to the car's potential shortcomings, in the interest of improving the car, or helping others, or having someone prove me wrong and help ME understand better. This car is fantastic, really, and it causes one to wish it were perfect, given the fact so much engineering was devoted to such a small car. I would have killed for something like this when I was a kid, and it's still very cool as an adult. Now on to some questions I have for everyone...
1. I could not get the esc to setup properly, and I tried dozens of times. The directions claim that, after the red light stays on and the green light goes out, to pull the trigger all the way full-throttle until the green goes on and the red goes off. Then move the throttle full reverse until the motor beginss spinning in reverse. This never worked for me, and the car only seemed to run well after I turned it off and just turned it back on, without attempting to set it up. Even then, reverse never really works well (full forward works fine, but it just sputters in reverse, and very slowly). I tried every combination of throttle-channel reversing, messing with the throttle trim, and so on. I am suspecting that the radio I'm using (I'm using an AM airtronics blazer temporarily) is just not compatible with the receiver, as I notice people are having good luck with Futaba's and those Perfex ones that come with mini-z's. What do you all think? Is the red light supposed to come on during full forward throttle, which mine does, or is the green supposed to, as I would have expected? Perhaps the esc is accidentally wired backwards to the motor (I can't tell, since the motor doesn't have any marks to distinguish between + and -)?
2. After 3 batteries, I burnt out the motor. I noticed it got very hot, but just ignored it as nobody seemed to have any problem with this. There is an enormous amount of clearance between the long side of the armature and the motor's bushing, but I figured this was just sound engineering as the motor easily could bind if the alignment was not perfect (which it can't be, given the fact the shaft is so long). What do you all think about this?
Thanks for your time,
Bravin Neff