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A customer sent this message:
Hi,
We are planning on buying one of your wheeled robot, the 4WD All Terrain Heavy Duty Robot Platform – IG52 DB
We would require it to move a payload of about 180lbs, at a speed of 170 ft/min, and it would need to be autonomous for 5 hours.
Compared to the standard configuration, we thought about using the higher torque IG52-04 24VDC 136 RPM.
We would surely also need to use other type of battery (like Li-ion) as we fear standard lead batteries won’t be efficient enough.
The robot would move indoor on a flat, sleek surface (concrete), and would mostly go on straight lines, with only 15 180° turns to do.
What do you think about this configuration, will it be enough for the intended use, or do you have any recommendation ?180 lbs is pushing it, but will likely be OK. If it’s smooth surfaces and 136 RPM motors, it will have a better chance. Should also chain couple the left axles and the right axles, so the two motors per side can work tougher (an option under assembly on the item page). Lithium batteries are recommended for the reduction of weight. Running autonomous usually works the motors more. Make sure you monitor the motors’ RPM compared to power input and prevent overload or stall conditions which will burn the motors. We would recommend keeping a temperature of each motor too if running for 5 hours. Autonomous motors will try to do what they are told, so they need feedback if worked too hard. Turning is the main issue with needed power for a skid steer. The more weight, the more friction, the harder to skid and turn… The HD chassis itself is more than capable of handling the weight. We also have 80 RPM IG52 motors, which would provide more torque, but lower speeds.
Customer replied:
OK, thank you.
Alas the 80 RPM motors are a bit too slow for us (we need to run at 150 ft/min, and with the 80 RPM we computed a speed of 140 ft/min), so I think we will stay on the 136 RPM. But maybe we could use another mean of reduction … Is it possible to choose another chain drive reduction (standard is rated at 14:21) ?
About the battery, I didn’t found Li-ion battery of enough capacity (i.e. at least 18 Ah for 12 V) on your website. Would it be possible to use batteries from another provider ? Can we buy an assembled robot without batteries ?Thanks for your reply
Yes we can change it some. no more than 14 to 24. 14 is the smallest that will fit on the motor shaft. 24 is going to be real close to rubbing the chassis with the chain. Just let us know when you place the order what chain reduction you want and we can make it happen. no cost impact for the non standard chain reduction.
As far as the batteries, the K2 batteries are great. You can run two 24V batteries in parallel to get ~20Ahr. we are out of stock right not, but have more than 60 on order, should be here in a week or two. http://www.superdroidrobots.com/shop/item.aspx/k2-25-6v-lifepo4-battery-pack-9-6ahr/1140/
we also have these that work well too. they are lighter, but its straight Lithium Ion versus LiFePO4 and will set you back a little more $. they can also be run in parallel, http://www.superdroidrobots.com/shop/item.aspx/high-power-polymer-li-ion-module-22-2v-10ah/969/
After having read the battery term, I’m a bit concerned about the shipping of the Lithium batteries. We are in France, so what whould be possible for the shipping of these batteries, and if it is possible, what delay for the delivery should we expect ?
I have another question about shipping: for the entire robot, what are the shipping options, their cost and their expected delays ?
Lithium batteries have a lot of potential (good and bad), To date they are not taking into account the many different chemistries of the batteries. All are just lumped into Lithium Battery category. LiFEPO4 is a lot more stable than staring Lithium and can take more defects and abuse before causing issues. However, we as the shipper have to treat them all the same. International shipping, forces us to use air shipping, which is restricted for Lithium Batteries. It can still be done, just more handling, making sure it doesn’t get on a passenger plane (cargo only). They recently require the batteries ship in a <30% energy state, which is easy to comply with, just have to discharge the batteries prior to shipment. There are also different regulations for batteries if they are shipped loose or installed in equipment. How many batteries, etc. So until we finalize the order, where its shipping to, etc. we can not provide a real impact other than there may be one up to including that we can't ship it no matter what via air.
All our robot kits provide the option to deselect batteries. We can still assemble it and test it, you would just need to install your own batteries that you get local. This may be the cheapest option because just the weight of the robot will be less, so shipping cost will be less. Sometimes it does not cost or delay anything additional, other times the batteries have to be split up in separate overpacks or can't ship at all. Sorry, best bet is not selecting a battery if you know air shipping has to be involved.
Wish it were easier,,, The regulations are constantly changing too.
Here are some links if interested.
http://www.iata.org/whatwedo/cargo/dgr/Pages/lithium-batteries.aspx
http://www.iata.org/whatwedo/cargo/dgr/Documents/lithium-battery-update.pdf
https://www.ups.com/media/news/en/ca/intl_lithium_battery_regulations.pdfThe best way to get all the costs down, etc. is just add what you want with the configuration options of the robot kit. Use the online shopping cart. Checkout. There are many areas during checkout for comments for addition things you want (like custom chain reduction, etc.). The cart may or may not calculate shipping depending on address, weight, size, etc. If it does not there will be a option to check for calculate and add to the order later. Don’t make a payment. Select quotation as the payment option. We will review, adjust, etc. the invoice and get it back to you with all the details you need.
About the torque problem, I’ve thought about another solution : use the 6 inch tires, and opt for a 14:18 ratio.
With this and the 136 RPM motor, the speed computer gives us 165 feet/min, 15 more than what we need so theoretically we are OK, with a good margin, and with the maximum torque we can have using the IG52 given our speed constraint.
So my question is: Is using a sprocket with 18 teeth on the gears possible with this robot ?
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