RC guys are smart, maybe powertool guys are smarter

With all the attention paid to the Dewalt A123 battery packs it seems that the Dewalt motors and gearboxes have been all but ignored by everyone but the battle robot guys. It seems a lot of the problems the RC guys are trying to solve have already been solved by Dewalt. Not only do we get the engineering, but we also get the cost reduction of mass production. Here's what the older model 24V motor and 2 speed gearbox can do when run at 36V (no tech details on the newer 36v motor & 3 speed gearbox other than the gearbox giving a 4:1 range, source http://www.robotmarketplace.com/products/dewalt_main.html)

24v Dewalt hammerdrill motor and 2 speed gearbox:

Motor RPM- 30,000+
peak efficiency- 81% (assumed at motor)
no load speed low gear- 675rpm
no load speed high gear- 3000rpm
peak torque low gear- 68 foot pounds
peak power- 2.2hp
no load current- 2.6A
nominal current- 68A
stall current- 190A
motor weight- 1.6 pounds
gearbox weight- 1.1 pounds

The circular saw version of the motor even has an electronic brake for, according to Dewalt, "longer battery life". To me that sure sounds like they have regen covered too! The motors are also blown to keep them cool. While the 24v hammerdrill is hard to find new, you can get the motor+gearbox for $113. The new 36v model and gearbox may be even better. I'd bet there are some guys around the forum who have them sitting in a box as leftovers from buying batts.

With 65 pages of discussion about using RC motors where solutions still have a lot of ???'s, how is it possible that a search turns up only 1 post and a couple of responses a year ago? At the very least these multi-speed gearboxes have a lot of potential for use with RC motors, since they're built for high rpm input and good power. I only have the 24V cordless circular saw, so I'm unsure if the gear shift is something we could easily rig to shift while riding.

For a bit of noise, it seems I can have my cake and eat it too. Cheap, simple brushed controller, multi-speed, powerful, less than 3 pounds, maybe even regen!!!!!!

John

Geeze, the three speed lends itself to the ridiculous possibility of up to 108 gears, if you have one of those crazy 36-speed bikes and a BB drive. :wink:

Link said:

Geeze, the three speed lends itself to the ridiculous possibility of up to 108 gears, if you have one of those crazy 36-speed bikes and a BB drive. :wink:

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I thought I only needed 2 for the motor, and bigger chainrings for me. The 3 speed box is interesting though, with 400-1200-1600rpm. 400 for steep hills, 1600 for fast cruising, and that 1200 may be perfect for grocery and/or kid hauling.

John

Sounds like a cheep Rolhoff! Way to go!!!!
otherDoc

John in CR said:

I thought I only needed 2 for the motor, and bigger chainrings for me.

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Thought. Past tense.

Link said:

John in CR said:

I thought I only needed 2 for the motor, and bigger chainrings for me.

Click to expand...

Thought. Past tense.

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I'm sure I could get by with a 2 speed, especially since most applications are single speed. That oddly spaced gear ratio in the middle has interesting possibilities. I was just poking around trying to find something off the shelf to use with an RC motor and retro-direct, then found something that may prove useful. It should keep me busy while I wait for my motors and controllers from Knuckles, and some multi-kw hub motors on the slow boat from several factories in China. I realize these probably couldn't stand up to the continuous use of a daily commuter, but I have the same doubts regarding RC motors. The brushes are only $5 and gearboxes are cheap enough to experiment, so I'm thinking a cheap little full suspension bike with 3lbs of motor, gearbox, and mounting bracket on the front wheel, plus the same on the rear, would make a fun to ride 2wd bike that could climb anything I threw at it, and still be capable of speeds requiring extreme care. Excluding batteries, it seems like a cheap bike could be turned into a high performance e-bike for under $400 (even less if I use drill parts for controllers and throttles) using parts I either have already or that I can purchase locally (a huge plus for me). No sluggish $400-500 20mph kits for me.

John

I suppose with a drill gearbox, you could use the clutch to prevent a total motor-stall.

Clearly, further testing is needed here. I wonder about the efficiency vs conventional ebike setups.

Hmm, it would be interesting to see what could be implemented while still retaining the warranty.
http://www.dewalt.com/us/warranty_information/popup_warranty_information.asp

Testing? The battlebot guys have already used them extensively, including hard data on the 24V model, not to mention the hundreds of thousands used around the world for their intended purpose. Being driven by a high speed brushed motors, I'd only expect brushes and gears to last in the hundreds of hours, so as the primary on a daily commuter I'd look elsewhere. On the other hand you could use a small hub motor on one wheel, over-volt it for high speed. Then add one of these to aid in takeoffs and hill climbing to turn that lackluster efficient commuter into a performance ride, using the hub motor only in the range where it is most efficient. Used in that manner, you could probably even use of most of the tool parts for motor, multi-speed gearbox, controller, throttle, and even batteries. Then all you'd have to do is figure out the mounting and add sprockets, freewheel, and chain. A simple and cheap solution for a non-kit, not to mention high power and multiple gears. BTW, the 36V hammerdrill (no batts)is going for $93 including shipping on EBay from a seller with 99.9% positive feedback and almost 50k sales.

John

No input from the RC crowd about whether the transmission is a viable multi-speed gearbox available directly off the shelf to use with RC motors?

John

Slick.....

http://www.youtube.com/watch?v=y8abvlYHK3Q

Trumpet said:

Slick.....

http://www.youtube.com/watch?v=y8abvlYHK3Q

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Wow, that is pretty cool! I'd bet one of these guys could adapt that drive system to a full size bike. They're not cheap but not ridiculous either at $629.

http://www.dpxsystems.com/ProductDetail.aspx?ID=184

Just saw this - the do it yourself drive system kit for $379

http://www.dpxsystems.com/ProductDetail.aspx?ID=199

Yeah I saw those CPX drives a while back and dismissed them for the price. If they really get 4mi of range, that's 20ah/mi. Not too bad considering the bike, power going to waste at only 14mph, and the extra gearbox with a 90° change in direction. Plus it's not taking advantage of the different speeds available in the transmission. This should calm eP's concerns about efficiency in the other thread to some extent. I'm going to try to take it into another realm of performance using 2 motors, better gearing, better controller, over-volting, less losses in the drivetrain, and making use of the multi-speed gearbox. Hopefully I can do better than shown in the video, but up a steep hill in low gear, but even if it's only 10mph in low gear, that would be 40mph on the flats in high gear using the 36v gearbox as in the clip...yikes.

John

I really don't think drills could handle the continuous loads of an electric bike or scooter. I remember mixing paint with my drill and feeling how scorching hot it got after wards, wondering if I damaged the motor. The robot guys only run like a total of 10 minutes of run time and replace parts almost every run so I really don't think their reliability is exactly proven. I think I would still rather go toward the RC side of stuff since they really put out crazy wattage numbers.

magudaman,

Agree, you are right, cordless tools of the last few years operate brilliantly for what they are designed to do making very usable alternatives to corded drills and are very reliable when used under typical site use. Read of lots of those motors being burnt out when mixing continuous use under load.

A gash power dill with duff batteries makes a potentially good source of a 2/3 speed transmission however with reduction ratios in the region of 10-40 ish.
http://www.chiefdelphi.com/media/papers/1592

I definitely appreciate that the motors can fail under heavy load since they'll go to high current with less ventilation. That's why I want to use the gear shift AND use 2 motors. I do have one question, what constitutes "continuous use" with motors turning 20-30krpm? It seems that just 10-15minutes would get you to the same point as over an hour continuous with a 2-3krpm motor. Without considering the higher power RC motors, I think you'd need to attach a blower to the RC motor before they become comparable, since in the designed use an RC motor has the prop wash for natural ventilation, and a blower is likely to reduce it to comparable efficiency. Then it's just down to the brushes.

Magudaman,
Digging through that link makes me even more excited try this, because at a minimum I'll end up with durable multi-speed gearboxes to attach to an RC motor. They highlighted durability with no failures, along with precise shifting on the fly. If the motors fail, then I get a pair of those $50-60 2-2.5kw RC motors and attach them to the gearboxes. Time to learn some RC stuff, so I can use a servo to change gears.

John

U may need a "sail winch" servo if the gear change is very hard to do. Another possibility is car door opener solinoids. Very high power.
otherDoc

docnjoj said:

U may need a "sail winch" servo if the gear change is very hard to do. Another possibility is car door opener solinoids. Very high power.
otherDoc

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Thanks Doc,

Perfect. Now which of my employees doesn't need his electric door locks?..hmmm

John

Great article about shifting the dewalt transmissions on the fly. Note that they are adapting the transmission for other motors.
http://www.okpreengineering.org/courses/2006_EDD_FIRST/03_Drive%20&%20Mechanical%20Systems/Team%20647_NothingButDewalts_Rev1_0.pdf

I think the car door opener solenoids are used by the custom car guys who shave off their door handles. Its not your run of the mill power door lock component. Some cars do come standard with these for the trunk tho- for the salvage yard rummagers.

Ted_Z said:

Great article about shifting the dewalt transmissions on the fly. Note that they are adapting the transmission for other motors.
http://www.okpreengineering.org/courses/2006_EDD_FIRST/03_Drive%20&%20Mechanical%20Systems/Team%20647_NothingButDewalts_Rev1_0.pdf

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Thats a really cool article,Ted! Do they mention any stats regarding h/p or torque for any of these motor combos?
otherDoc

In the article it says that there is no back drive option. I'm interpreting this to mean that the transmission doesn't turn, or at least doesn't transmit torque, in the reverse direction. If that's the case this transmission may not be usable for regeneration applications.

lepton said:

In the article it says that there is no back drive option. I'm interpreting this to mean that the transmission doesn't turn, or at least doesn't transmit torque, in the reverse direction. If that's the case this transmission may not be usable for regeneration applications.

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Hi,

I think it means with the no back drive pins in place it won't spin at all in the reverse direction.

I definately like the trnsmission idea. Great application!

My only concern was already mentioned------------- Long duration use.

That being said, there is no way of knowing untill someone buys one and tries it out. I think a good RC motor coupled to one of the transmissions could be a very good hybrid drive system.

Matt

The transmission does have "no back drive" pins, but they can easily be removed. I've used these transmissions before in hobby robot aplications.