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Old Aug 08, 2008, 05:50 PM
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Integy Lathe Motors

It seems hard to find good info on the popular Integy lathe motors, so I thought I'd collect some here.

These motors are intended for driving slow speed armature lathes. 500 frame size, with good bearings, replaceable brushes, etc, like any nice RC car motor... but they are wound with high turn counts of finer wire, meaning they turn slower for any given voltage than "hot" motors. Outside of lathes, they've proven popular for RC rockcrawlers and Springer tugs, amongst others.



Integy offers them in 35, 45, 55, 65, 75, and 85 turns. But they give no specs for KV, the number that reveals the free-running speed on any voltage. I asked on their tech forum, but got a totally bogus answer... So how to figure out which one will come close to direct-driving my 45mm prop at the desired 7000 rpm on 12v? I'm clueless! I hate clueless, so I bought one and measured it.

How to measure? Chuck it in a drill press that gives a known speed. Run it and measure the voltage generated across the tabs (yes, spinning a motor turns it into a generator). Calculate KV = drill press rpm / generated volts.

I bought a 55T. Ran it at 3100rpm and got 2.86v. 3100/2.86 = 1084 = the KV value.
How fast on 12v? 1084 rpm/v X 12v = 13,000 rpm. Too fast!

So now I have an 85T on order.
Anyone else have any others they can do this on? I'll list them here!

Integy Lathe
Motor (3 pole)___KV_____RPM on 12v
35T____________1730______20,760 (estimate)
45T____________1358______16,296
55T____________1084______13,000
65T_____________930______11,160 (estimate)
75T_____________806_______9670 (estimate)
85T_____________714_______8571

VacUBoat 545:____424_______5090 (5 pole)



Note: More turns is NOT like gearing down- it doesn't give higher torque! It's likely to be a slower AND weaker motor! But props on slow scale boats (not racers or planing boats) don't need much torque.
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Old Aug 08, 2008, 08:35 PM
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Links:
Integy Lathe stuff: http://www.integy.com/cgi-bin/webc.c...tml?p_catid=26
But a better price at: http://www.rcplanet.com/SearchResult...ch=lathe+motor
Vac-U-Boat 545: http://www.vac-u-boat.com/KitsParts.htm
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Old Aug 08, 2008, 08:52 PM
Grumpa Tom
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Pat, I recently saw some 100T motors advertised for sale. When I find them again I will post it here.
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Old Aug 08, 2008, 08:59 PM
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Remember it's not just TURNS (number of wraps around each pole of the armature). The VacUBoat specs hint that their 5-pole motor might have 75 turns... which says "slow" on 12v (it's designed for moderate speed on 24v)... but the wire gage used also is a factor. Finer wire, same number of turns, offers more resistance so will yield a slower motor yet.

Integy also has a "V11" series with high turn counts, but stronger magnets... which could increase torque (and maybe speed?) for the same turns.
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Old Aug 08, 2008, 09:19 PM
Grumpa Tom
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Yeah yeah yeah blah blah blah

I'm just lettin' ya know someone is making a 100T motor for sale.
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Old Aug 08, 2008, 09:22 PM
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I mentioned getting a desired prop speed above... and what speed should that be? Well, as I've pointed out numerous times, www.raboesch.com 's prop catalog lists max recommended speeds for their scale props (racing props: whole another story...). It doesn't seem to matter which style of their prop, it just goes by diameter. Don't know if it's a hydrodynamic thing (onset of cavitation?), or just the speed where their soldered blades are no longer safe .

But just for reference, here it is.

p.s., Do I like Raboesch especially much? Nah... their stuff is nice and is readily available-- BUT they are the only outfit that actually thinks we're smart enough to give us real data...


10/2010 edit: Now I have less reason to like Raboesch... they dropped the speeds from their catalog! I wrote a letter of complaint to them, got no reply... But hey, I still have the old data...
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Old Aug 08, 2008, 09:23 PM
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Engineers are like that.
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Old Aug 09, 2008, 12:24 AM
NeverAgainVolunteerYourse lf
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Point of interest, Ive got a 40 mm raboesch and 2 75mm, the 40mm is really good at 5000 rpm (springer) I've ran it at 10 000 rpm, its ridiculous. the 75 mm props are great below 3500 rpm, Ive spun them at 10 000 rpm as well and got huge current draw.
Newer bubblejet printers have a 550 size can motor in it wound for 24 or 36 volts. They have a rpm of around 2500 at 12 volt. the printers are c**p so readily get ditched and can be had for free. Only drama is the pile of useless junk you then have to get rid of.
Nick
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Old Aug 09, 2008, 02:32 AM
Grumpa Tom
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Funny, I thought I posted a link a couple of hours ago. Hmmm.......

Well, here it is again. A link showing motors up to 100 Turn:

http://www.rcmart.com/rc-rss/2008/07...or-gear-ratio/
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Old Aug 09, 2008, 08:16 AM
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Nice find, and another source- AND they list speeds! On 7.2v. For 12v speed, just multiply the given speed by (12/7.2). BUT, they're 50% wrong when they say:

" "T” means “Turn”. A lower turn value produces less torque but higher speed. A higher turn value produces more torque but lower speed."

Wrong. Lower speed AND less torque is what you'll get. One befuddled rock crawler wrote how his Integy 85T was worthless- gave him nice low speed, but it stalled out on the smallest hill. Duh. And even there, someone responded: For TORQUE, use lower turns (faster motor), and gear it down for torque. Again, a high turn, low speed/low torque motor CAN be fine for a scale prop which doesn't demand much torque. But a prop which does demand torque (like my 4" tug prop) will just need a bigger frame size motor with high turns to deliver direct drive low speed torque. That's why I put the huge American Bosch motor in my tug.
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Old Aug 09, 2008, 09:28 AM
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There's no single characteristic of a motor that determines it's torque, or power, or the amount of work it's capable of doing. Several of those characteristics have to be considered 'together'. The same holds for the 'speed' of a motor, the number of turns isn't the only consideration. In either case, it isn't exactly a simple thing to figure. But, it's all physics, and if you want to go through the whole 'figuring' process, the amount of 'strength'/torque, and 'speed' can certainly be calculated. (It's been something like 40 years since I had to do that in college, so I know it can be done. Didn't say I was any good at it, and since I haven't used it since then, don't even think about me trying to do the figuring thingy, too lazy! )
All the above will do is give you the 'numbers' for what will be available at the motor's output shaft. Says nothing about what happens when you connect the prop to it, or how. That requires another step of two in that 'figuring' process. (A spread-sheet program ought'a make that a sort of 'plug-n-play' thingy... hint hint for those 'spread-sheet' guru's out there?)
The number of variables in that programming will probably take a few days...oops!... years(?) to gather. (~I~ don't even wanna thing about that part!)
The simplest, most often 'wrong' but still close 'fudge factor' type advice is 'bigger is better' to some absolutely ridiculous point. Then you gotta power the thing, and make the boat big enough to hold all that stuff, and convince your "significant other" that you should do it. The first part just takes time. Good luck on the 'convincing' part!
- 'Doc

PS - When you get all of that done, I think you should publish it 'free' for the rest of us!
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Old Aug 09, 2008, 09:35 AM
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That's why I'm happy to start with the KV value, which is the result of all the physics that I don't want to drege up! KV gives you free-running speed on a give voltage; then, experience and/or trial+error will let you decide if a 400/500/600 size motor is what you need for torque for a given prop.
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Old Aug 10, 2008, 10:35 PM
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Quote:
Originally Posted by patmat2350
It seems hard to find good info on the popular Integy lathe motors, so I thought I'd collect some here.

These motors are intended for driving slow speed armature lathes. 500 frame size, with good bearings, replaceable brushes, etc, like any nice RC car motor... but they are wound with high turn counts of finer wire, meaning they turn slower for any given voltage than "hot" motors. Outside of lathes, they've proven popular for RC rockcrawlers and Springer tugs, amongst others.



Integy offers them in 35, 45, 55, 65, 75, and 85 turns. But they give no specs for KV, the number that reveals the free-running speed on any voltage. I asked on their tech forum, but got a totally bogus answer... So how to figure out which one will come close to direct-driving my 45mm prop at the desired 7000 rpm on 12v? I'm clueless! I hate clueless, so I bought one and measured it.

How to measure? Chuck it in a drill press that gives a known speed. Run it and measure the voltage generated across the tabs (yes, spinning a motor turns it into a generator). Calculate KV = drill press rpm / generated volts.

I bought a 55T. Ran it at 3100rpm and got 2.86v. 3100/2.86 = 1084 = the KV value.
How fast on 12v? 1084 rpm/v X 12v = 13,000 rpm. Too fast!

So now I have an 85T on order.
Anyone else have any others they can do this on? I'll list them here!

Motor__________KV_____RPM on 12v
35T
45T
55T____________1084______13,000
65T
75T
85T
VacUBoat 545:____424_______5090

Note: More turns is NOT like gearing down- it doesn't give higher torque! It's a slower AND weaker motor! But props on slow scale boats (not racers or planing boats) don't need much torque.

Here are a couple specs missing from your chart there. I've been doing some testing too.

45T Integy- KV=1358 ___ RPM@12V=16,296
85T Integy- KV=714_____ RPM@12v=8571
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Old Aug 11, 2008, 06:41 AM
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Thanks, list updated!
That 85T looks like it should work for my current application...
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Old Aug 11, 2008, 10:29 PM
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Ya, they work really well when connected to a 2:1 or 3:1 gear reduction unit. Plenty of torque and just right right amount of RPM for scale models like decent sized tugs.

You should check these out. If used them direct drive on 12volts and they work pretty good. Especially if you were to run them on a 2:1 reduction. I would'nt recommend them direct drive with props bigger that 2" though. On 6 volts you could use a bigger prop but I still wouldn't get too carried away. I've used them before for many applications like boats and rock crawlers. Plus the seller is reliable, I've bought some of them from him before

http://cgi.ebay.com/MABUCHI-12-VOLT-...QQcmdZViewItem
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