Hey and hello to Part 2 of the "Anatomy of a RC Crawler" by Sabaot.
Previously, in Part 1 we discussed topic about radios, transmitters, receivers, other stuff related. Now we can move to next
part - what a RC Crawler is anyway?
A Crawler is a kind of a RC vehicle (a car or a truck) designed and build for a slow moving in a really hard terrain that
normal vehicles would stuck. And by hard terrain I mean deep sand, mud, water (streams), rocks, logs, tall grass, snow,
gravel, roots... you got the picture.
What makes Crawler so special? Well, its design. You will know you are looking at Crawler when you see one (sometimes
you can confuse it with monster truck as both designs share some common things). First thing are the wheels - they are
huge in comparison to overall model. The wheels are way bigger than in normal car, even as in a 4x4 Truck. They stick out
from the body providing a large base. Tires are deeply threaded to porvide maximum grip on a loose surface.
Next thing we notice is suspension. Model's body connects with those big wheels with large and long shocks. They move
quite easily and have a tremendous travel range (again, comparing to normal cars). This is due to fact that a Crawler
moves in very hard terrain and thanks to that flexible suspension design it can overcome deep/high obstacles simply by
driving over them without hanging/stucking.
As we are with hanging - Crawlers have their body very high above the groung which makes a large clearance between
ground and body. This also help running over obstacles (combined with large tires and long suspension travel), model can
pass it without a danger of hanging. To make it very clear, imagine that: ahead of you there is a road bump (speed limit)
and you drive Bugatti Veyron... you need to get over it very carefully while a guy in Toyota HiLux runs at top speed without
even noticing. Same with Crawlers - the greater clearance the bigger obstacles you can overcome.
Closer inspection shows interesting design feature - hard and fixed axles. One would thought that independent suspension
would be better. Well, I'm no an expert in that case (clarification needed) but I think that fixed axles affects overall
clearance. With independent suspension, while getting on an obstacle, only one wheel gets lifted while the rest of a
Crawler remains fairly the same level. So while wheel goes over obstacle the rest of a model don't and there is a danger of
getting stuck.
On the other hand fixed axles works as a lift for a model. While driving wheels go up and down, pushing shocks and
compressing them. But as one wheel goes up the whole Crawler tilts/pans and still have rahter large clearance. In my eyes
this the advantage of fixed axles over independent suspension.
What's next... propulsion. When you look at a Cravler from a side or from underneath you will notice weird sticks coming
from axles towards and up the center (more less) of a model. Those "sticks" are drive shafts and they transmit power and
torque from a motor to the wheels.
But why there are two shafts? Because Crawlers are vehicles equipped with all wheel drive system - names for that are:
4x4, 4WD (four wheel drive), less commonly AWD (all wheel drive). Typical car is a 2WD (either front or rear axle,
depending on design), some trucks and army/special units have 6x6, 8x8 drives. Ok, back to topic - all we need to know
that all wheels can move. This is vital for Crawler's ability to... crawl. Or climb. Or go thru mud...name it. 2WD drive will
either push or pull, 4WD does both at the same time. That's why we see two shafts, each transmits power to the one axle.
You can ask - why not to use simple and straight shatf instead of those "bent" ones. The answer is: movement. As Crawler
moves thru terrain its suspension works hard, moves up and down and so the torque transmitting shatfs. Without them the
whole suspension would be stiff and be more like a child's toy, bumpy.
Last but not least - steering. Simple Crawlers have a single servomechanism (small electric motor with some electronic,
encased in hard cover with sticking out moving arm that is able to move in a typical arc of 60 deg.) that is attached to front
axle and wheels via control rods. Arm's movement forces wheels to turn. Some Crawlers possess ability to turn both front
and rear wheels independetly. Tho it's possible to have front and rear move in the same time but opposite, but it's just a
theoretical option and I don't believe that anyone will try to implement it as a permanent solution.
And it would be all for today. Part 2 is over, stay tuned for next one. If you liked it - leave a comment. YOu found a mistake,
don't like something - feel free to comment as well. I try to pass all I know but I'm aware of my limitations and I don't have
a right for omni-knowledge. The more you correct me the more accurate and proper this work will be. So speak up, ask for
more. If I'd know I'll try to help.
Untill next time.
Previously, in Part 1 we discussed topic about radios, transmitters, receivers, other stuff related. Now we can move to next
part - what a RC Crawler is anyway?
A Crawler is a kind of a RC vehicle (a car or a truck) designed and build for a slow moving in a really hard terrain that
normal vehicles would stuck. And by hard terrain I mean deep sand, mud, water (streams), rocks, logs, tall grass, snow,
gravel, roots... you got the picture.
What makes Crawler so special? Well, its design. You will know you are looking at Crawler when you see one (sometimes
you can confuse it with monster truck as both designs share some common things). First thing are the wheels - they are
huge in comparison to overall model. The wheels are way bigger than in normal car, even as in a 4x4 Truck. They stick out
from the body providing a large base. Tires are deeply threaded to porvide maximum grip on a loose surface.
Next thing we notice is suspension. Model's body connects with those big wheels with large and long shocks. They move
quite easily and have a tremendous travel range (again, comparing to normal cars). This is due to fact that a Crawler
moves in very hard terrain and thanks to that flexible suspension design it can overcome deep/high obstacles simply by
driving over them without hanging/stucking.
As we are with hanging - Crawlers have their body very high above the groung which makes a large clearance between
ground and body. This also help running over obstacles (combined with large tires and long suspension travel), model can
pass it without a danger of hanging. To make it very clear, imagine that: ahead of you there is a road bump (speed limit)
and you drive Bugatti Veyron... you need to get over it very carefully while a guy in Toyota HiLux runs at top speed without
even noticing. Same with Crawlers - the greater clearance the bigger obstacles you can overcome.
Closer inspection shows interesting design feature - hard and fixed axles. One would thought that independent suspension
would be better. Well, I'm no an expert in that case (clarification needed) but I think that fixed axles affects overall
clearance. With independent suspension, while getting on an obstacle, only one wheel gets lifted while the rest of a
Crawler remains fairly the same level. So while wheel goes over obstacle the rest of a model don't and there is a danger of
getting stuck.
On the other hand fixed axles works as a lift for a model. While driving wheels go up and down, pushing shocks and
compressing them. But as one wheel goes up the whole Crawler tilts/pans and still have rahter large clearance. In my eyes
this the advantage of fixed axles over independent suspension.
What's next... propulsion. When you look at a Cravler from a side or from underneath you will notice weird sticks coming
from axles towards and up the center (more less) of a model. Those "sticks" are drive shafts and they transmit power and
torque from a motor to the wheels.
But why there are two shafts? Because Crawlers are vehicles equipped with all wheel drive system - names for that are:
4x4, 4WD (four wheel drive), less commonly AWD (all wheel drive). Typical car is a 2WD (either front or rear axle,
depending on design), some trucks and army/special units have 6x6, 8x8 drives. Ok, back to topic - all we need to know
that all wheels can move. This is vital for Crawler's ability to... crawl. Or climb. Or go thru mud...name it. 2WD drive will
either push or pull, 4WD does both at the same time. That's why we see two shafts, each transmits power to the one axle.
You can ask - why not to use simple and straight shatf instead of those "bent" ones. The answer is: movement. As Crawler
moves thru terrain its suspension works hard, moves up and down and so the torque transmitting shatfs. Without them the
whole suspension would be stiff and be more like a child's toy, bumpy.
Last but not least - steering. Simple Crawlers have a single servomechanism (small electric motor with some electronic,
encased in hard cover with sticking out moving arm that is able to move in a typical arc of 60 deg.) that is attached to front
axle and wheels via control rods. Arm's movement forces wheels to turn. Some Crawlers possess ability to turn both front
and rear wheels independetly. Tho it's possible to have front and rear move in the same time but opposite, but it's just a
theoretical option and I don't believe that anyone will try to implement it as a permanent solution.
And it would be all for today. Part 2 is over, stay tuned for next one. If you liked it - leave a comment. YOu found a mistake,
don't like something - feel free to comment as well. I try to pass all I know but I'm aware of my limitations and I don't have
a right for omni-knowledge. The more you correct me the more accurate and proper this work will be. So speak up, ask for
more. If I'd know I'll try to help.
Untill next time.