2010 talk:Mechanical 2 01.23
Extensive Email discussion on Drive and Weight considerations
-----Original Message-----
From: Dave Vadas [1]
Sent: Friday, January 22, 2010 5:05 PM
To: 'Lewis Jr, Larry'; 'Mike Wolf'; 'Thomas Kanzler'; 'Cavaliere, Thomas M'; 'Dal Santo, Tony'; 'Jeff Downs'; 'Gannon, Joshua'
Subject: RE: Worldwide Electric Corporation - Aluminum reducers
Larry,
Again... it needs to be worm drive reducer so that it does not back drive when in the cocked position. You get that for free with a worm gear... and it is mechanically fail safe
Even a planetary at the high ratios will not do that. With using just a planetary of any type would either require using either a one way over turning clutch (commonly called a conveyor back stopper), an electronic brake or a catch trigger... or you could try to play a risky balancing game and attempt to PWM stall the motor against the load holding it back... but that will burn up a ton of juice and produce a lot of heat and when power is dropped the kicker will fire... totally not safe.
We planned to use either 1/2 timing belt or chain. V-belts were just easy and cheap to implement in the prototype with off the shelf stuff.
You are somewhat right regarding V-belts... but also they are the prime choice to be used in varying and impulse drive situations, they take shock loading well. Chain is not recommended in those cases... they beat the heck out of roller chain... Chain called silent chain is used in those applications... Timing belts are ok and you do see them used in drag racing motor cycles.
The kicker by design is an instantaneous impulse mechanism, releasing all the energy stored in the surgical tubing (the system) instantaneously... by design, the drive does not see all the huge impulse because of the mechanical advantage of the drive going to infinity as it moves to the trip point... what the drive sees is a large varying load from 0 inlbs. to 500 inlbs. and back to 0 inlbs. during the 180 degrees of the pull back stroke.
We will discuss all of this in detail tomorrow. TGIF...)
Best Regards,
Dave Vadas
VP Professional Services & Solutions
www.AssurX.com
mailto: dvadas@assurx.com
Phone: 408.778.1376 x713
Fax: 585.486.6520
-----Original Message-----
From: Lewis Jr, Larry [2]
Sent: Friday, January 22, 2010 4:00 PM
To: Dave Vadas; Mike Wolf; Thomas Kanzler; Cavaliere, Thomas M; Dal Santo, Tony; Jeff Downs; Gannon, Joshua
Subject: RE: Worldwide Electric Corporation - Aluminum reducers
Dave,
I guess I am still a little concerned using the gear reducer that you want to use. Maybe you can go over it more in fine detail tomorrow to make sure I understand.
In the meantime, I did find this on banebots website.
http://banebots.com/pc/P80K-nnnn-0005/P80K-4433-0005 <http://banebots.com/pc/P80K-nnnn-0005/P80K-4433-0005>
It is the same gear box we are using for the drive but at a 144:1 reduction. Moreover, it weights 3.75lbs. In addition, if that ratio will not work they have a 192:1 version. The nice thing about these is that they are made to interface with the CIM motor where the reducer you are looking at I am not as sure about.
Also, are we going to be using V-belts on the pull back mechanism? I don't know if that is really the best application for them. Usually I see V-belts in applications that are high-speed low torque, but chain on the other hand is used more in low speed, high torque scenarios. I am concerned that we may have the belts slip when pulling back the device. Maybe I am just a little jaded from last years V-belts. I don't mind us using it for prototyping but I would prefer chain in the actual design if possible. I think that the sprockets may be lighter than the pulleys as well.
I feel a little better about the weight breakdown but 5lbs hear and there really adds up when we still don't have a majority of the robot weight and parts accounted for. I guess I would like to start to see a BOM with a weight budget once we start to cad up items.
Does anyone else have any thoughts on this?
Larry
________________________________
From: Dave Vadas [3]
Sent: Fri 1/22/2010 3:39 PM
To: Lewis Jr, Larry; 'Mike Wolf'; 'Thomas Kanzler'; 'Cavaliere, Thomas M'; Dal Santo, Tony; 'Jeff Downs'
Subject: RE: Worldwide Electric Corporation - Aluminum reducers
Larry,
Not a problem... were on it:)
The prototype no way represents the actual real design regarding component
that will be used.
See the attached... we are planning on using an aluminum series size 40 with
a 10:1 reduction. Its weight is 5 pounds:) The box on the prototype weighs
approximately 35 pounds:)
Additionally, the prototype steel drive dog pulley, 2 steel pillow blocks,
steel shafts, steel drive dog arm probably weighs 20+ pounds and all the
80-20 and brackets probably weighs 20 pounds... with the 35 pounds of the
worm gear box that's an approximate total of 75 pounds... also remember
there is plywood for the prototype controls board... no where what the real
design will be... say that will be 1/4 of the prototype... that's like
approximately 20 pounds...) What did we figure for the kicker weight
allocation?
Relative to the kicker operation...
Using the mentioned aluminum worm gear reducer in conjunction with the CIM
motor 12:1 reducer and the pulley ratio from the worm gear output to the
drive dog pulley of 1.25 will result in a total reduction ration of 150:1.
With CIM motor rpm rated at 5000 rpm that will result in a drive dog
rotation of 33.33 rpm or 1.8 seconds per 360 cycle.
Remembering that the home position of the kicker is just prior to the "trip
point"... and that it requires approximately 60% of the drive dog rotation
to retract the kicker toe to back inside of the drive frame vertical plain
after it fires... that rpm will result in the kicker toe being outside of
the drive frame envelope for approximately 1 second... which is 50% of the
specification allowed 2 seconds.
Remember the purpose of the a worm drive is to provide reduction and at the
same time to prevent back driving of the kicker when it is pulled back in
the cocked ready to fire position, holding back the large firing force
(40-80 pounds?)
Larry, does that eliminate your concerns?
How did it drive last night?
Best Regards,
Dave Vadas
VP Professional Services & Solutions
www.AssurX.com
mailto: dvadas@assurx.com
Phone: 408.778.1376 x713
Fax: 585.486.6520
-----Original Message-----
From: Lewis Jr, Larry [4]
Sent: Friday, January 22, 2010 2:22 PM
To: Dave Vadas; Mike Wolf; Thomas Kanzler; Cavaliere, Thomas M; Dal Santo,
Tony; Jeff Downs
Subject: RE: Worldwide Electric Corporation - Aluminum reducers
Dave,
Isn't that gear reducer really heavy? Can we get the same effect using a
transmission and a CIM motor where the turns ration is relativly high like
27:1? We weighed the robot last night and it was 126.6lbs!!!!! I know it
isn't our final design but there really is not much on there other than the
kicking mechanism and part of the drive train. I am getting really
concerned with weight right now since we haven't even added all the parts on
the drivetrain yet and we still need to add the hanging and self righting
mechanisms. We need to start to put together a weight budget and look into
some lighter materials. I know it is just a prototype but we need to start
thinking about these things now.
Larry
________________________________
From: Dave Vadas [5]
Sent: Fri 1/22/2010 2:17 PM
To: 'Mike Wolf'; 'Thomas Kanzler'; 'Cavaliere, Thomas M'; Dal Santo, Tony;
Lewis Jr, Larry; 'Jeff Downs'
Subject: Worldwide Electric Corporation - Aluminum reducers
Tom and all,
Here is the link to the WWE product PDF... Aluminum series starts on page
23.
http://www.worldwideelectric.net/Brochures/Gear%20Reducer%20Products.pdf
Here is their man site.
http://www.worldwideelectric.net/
the guy in the picture in the upper left corner is the one who is taking
care of us... and supplying us with whatever we need for little or no
charge... great guy... his name is Mike Bennett... he works directly for the
2 founders shown on the web site...
Unbelievable that they built this company based in Rochester to a 60+
million company in 12 years selling non precision gear boxes and motors...
Best Regards,
Dave Vadas
VP Professional Services & Solutions
www.AssurX.com <http://www.assurx.com/>
mailto: dvadas@assurx.com <mailto:dvadas@assurx.com>
Phone: 408.778.1376 x713
Fax: 585.486.6520
