hi I'm Ronan and I'm John
in this video we'll be giving you more information about lifts and extensions for FTC
we will discuss different mechanical options for extending and powering
along with how to detect that the lift is retracted and how to install wiring
this is a follow-on to our first lifts and extensions video and
we would recommend that you watch that first if you haven't done so
there are many different properties to consider when comparing these options
including the size, how wide and deep each option is, and its weight to length ratio
for this we will weigh different options
with the standard extension of 36 inches or roughly 90 centimeters
we will also measure how stable it is by extending
it horizontally and putting a one kilogram load on the end
aluminum extrusions such as these by REV robotics can be connected to
each other using these double-sided Delrin sliders
this assembly is 82 millimeters wide but is very light 490 grams per 90 centimeter extension
with a load they bend 4.5 centimeters in the forward direction and 10.8 centimeters sideways
there some friction when extended or retracting due to the rubbing
of the Delrin sliders against the aluminum
if they are impacted while extended most of the force is against the
Delrin plastic pieces which may not hold up against extreme force
to power them with strings REV provides small bearings which can
be screwed into the aluminum extrusion and then attached to a motorized spool
however 3D printed bearing covers are needed to prevent the string from falling off
to extend to 90 centimeters this requires five slides
which can be bought for about forty dollars total
on the REV robotics websites which is one of the cheaper options out there
aluminum drawer slides such as these Misumi SAR230 slides can
be connected to each other with these 3D printed or CNC pieces with bearings
they provide a compact and light solution only 41
millimeters wide and 520 grams per 90 centimeter extension
when extended to 90 centimeters it droops 9.5 centimeters in the
forward direction and 2.5 centimeters to the side
these drawer sides have very low friction when compared to
other options due to their roller bearings
they are hard to mount due to their limited number of holes
you may need to drill additional holes for mounting to a kit chassis
3D printed parts are also required to attach the bearings for stringing
this option is expensive though adding up to about
75 to 100 dollars for 90 centimeter extension from the Misumi website
there is a discount to 15 per slide if you buy more than five
aluminum xrails such as these by actobotics or gobilda are
connected using these end caps and use a classic pulley system to extend
they are very smooth and easy to mount due to this design
there is very little friction while extending and attracting
it is difficult to maintain all of these wheels
at the correct tightness which can lead to reliability issues
when extended 90 centimeters with a one kilogram
load it droops about five centimeters forward and 8.5 centimeters sideways
and weighs 700 grams so they are one of the heaviest options
also measuring 88 centimeters wide
this fully prepared system costs about 75 dollars from ServoCity
now we'll talk about some other options that aren't used as often
these linear rail slides sometimes called mgn rails are made of steel
and have a roller bearing block which moves along
the movement is very low friction because of
the ball bearings and the steel structure makes it very strong
we didn't connect these together to measure droop but we suspect the droop will be very
low because of the rigidity of the steel and the tightness of the blocks
they would be difficult to mount and you will probably need to
drill extra holes into the steel to connect them to your chassis
additionally you need 3D printed parts to attach multiple slides and bearings
enough of these mgn12 slides for a 90 centimeter extension
weighs 1250 grams making it the heaviest option
the cheaper option can be bought on eBay for 17 dollars each
you have to be careful when removing the blocks to avoid having the ball bearings fall out
similar options from Misumi or Igus can be 100 or more per slide
in summary this table shows you the main properties of the previous options
this is a lead screw style lift
it works by utilizing a spinning lead screw to move a platform up and down
it is incredibly strong and supplies a rigid platform without much flex in either direction
we and many other robots utilized this style of lift in the Rover Ruckus year to hang our robot
when joined with a high RPM motor it can move at a moderate speed
another advantage is its simplicity as it does not require a lift string
a major disadvantage is its limited range it can only extend the distance of the lead screw
another disadvantage is its speed it takes about
three seconds just to travel the length of the lead screw
there are several ways to power a lift the most common method is to run strings
through to a spool connected to a motor in a continuous path
we discussed this in our first lifts and extensions video
to enhance the control of your lift a pull down string
is highly recommended even for vertical lifts
they increase speed going down and keep the pull-up strings on the pulleys
sometimes they can have varying levels of slack throughout the lift
using a spring attached on the end will solve this issue
it's very common to use multiple motors to power the lift
when doing so it's important to mechanically connect the two with either gears chains or belts
if you are extending horizontally another option to power it is with a linkage as shown here
this is the fastest method for powering linear movement
make sure to keep the motor axiss and the pivot
axis perfectly linear to push the slides out as the motor rotates
the linkage also serves as a return method for the extension
be careful with the motor or servo that you choose as it will need a lot of torque
lifts require a way to stop so they don't go down too far and
risk strings falling off the spools especially if there's no return string
sensors are the best way to do this
this is a REV magnet sensor it detects the
magnetic fields of a magnet and returns a true or false
it requires a strong magnet but is easy to mount and doesn't need contact
this sharp analog distance sensor sends infrared rays out and then
measures the reflected IR values after bouncing off of something
it needs a large object to detect when a lift is at the endpoint
these are easy to mount and do not require contact
limit switches or touch sensors sense physical contact
we have found that the lift is prone to bouncing when hitting a limit switch
limit switches are also harder to mount due to the non-standard hole layout
in summary here are the pros and cons of different options for sensing that the lift is down
to power the electronics at the end of your ellipse cable management is required
this coiled cable is easy to mount but comes in a set number of wires and lengths
it is prone to catching due to every retraction having a slightly different path
a cable drag chain as shown here can protect any number of wires and is fairly easy to mount
it only comes in some set lengths but can be extended
the downsides are that it takes more room than
the other options and removing or adding wires is difficult
this video shows a wire loom it can be any length
and any number of wires but it is hard to mount and perfect
once it is functioning properly the extension
retracts perfectly every time and is easy to take out wires
the final option is to create your own large coil
as we did for skystone this takes up a lot of space and is hard to set up
it allows for many lengths and numbers of wires
in summary here are the pros and cons for the different options of putting wires through a lift
we hope you found this information useful
as always you can contact us via Email Discord Instagram or leave a comment below thank you