Expensive Neugart 40 vs cheap Nema 23?

Nema 23 5:1 are dirt cheap compared to Neugart PLE 40

Does "What you get is what you pay for ? " apply ?

Nema 23 Specs : https://cdn.automationdirect.com/static/specs/suregearsteppergb.pdf

Neugart PLE 40 Specs : http://www.motionusa.com.s3-website-us-east-1.amazonaws.com/neugart/PLE_Series_Inline_Economy.pdf

Input max rpm is too low on the Nema.

Well I first shared the same thought but it seems to be the same max speed for the Neugart on specs page 7 ? Or did I misunderstand ?

Do these numbers really apply to our cases, where it runs maybe 2 hours per year?

I’m looking at page 5.
If you’re running 12s with 500kv, you’re spinning 25k rpm at full throttle, full battery @ 50.4v

Depends if you’re only planning to run it 2hr/year. I’m planning to run mine a lot more than that…I’m building for production quality, not for alpha level prototype.

High rpm seems to be a problem, also nominal output torque is higher with the original. As delivery times are high for the original I’m considering this one: Pl40 One Stage Planetary Gearbox Ratio 3,4,5,6,8 - Buy Nema 17 Planetary Gearbox,Stepper Gearbox,Gearbox For Cnc Machine Product on Alibaba.com
RPM is not high enough as I plan with an input speed of 18000 rpm but torque is quite good with 18Nm for the 5:1 version.
Question is how long the bearings last at high speeds.

Ive often wondered if temperature is the prime motivator for the max RPM specs. Maybe the gearbox gets too hot, the grease inside becomes too thin to adequately lubricate or perhaps components begin to expand slightly and cause binding in areas that require tight tolerances to be maintained?

If that’s the case I know where we can find a bunch of coolant…

can anyone comment on gearbox temp during hard operation? It would be really cool to put the eagle tree temp probe down there although wire length/ material used to extend the wire down the mast may affect accuracy. Not sure if eagle tree probes are thermistors or thermocouples (or maybe even RTD’s)

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How about testing this in the workshop? Just let it run for some time with a load on it.

Something I do not understand . As per above specs, Neugart PLE 40 is rated at 5000 rpm input max. But people like Pacificmeister use 500kv at 10s… That is waaaaaay more RPM… Deutsche qualitat ?

Rating gears is difficult and there are many aspects to it. Things that are affecting them and their bearings are: heat, load, temperature, RPM and if there are load spikes. To calculate the lifetime, you combine all these factors in formulas together with some variables from the manufacturer and get an estimate. Reducing any of those variables increases the lifetime.
3 things that shorten the lifetime considerably are shock loading (going from forward to reverse instantly), excessive heat (unhardens the teeth) and lack of lubrication (with lubricant, the teeth never actually touch).

These gearboxes are probably used by industry to run for several years. Since we are only using them for a few hours, they could very well survive at higher speeds.

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20,000hrs is OK, 6,000rpm isn’t super, so i would say you could use a motor like the 6374 168kV outrunners from Hobbyking, 12S and aim for 6,000 rpm loaded. Make your esc limited to 6,000rpm and you have to keep torque under 6Nm (middle sized one 5:1) or you’ll reduce it’s life. the 5:1 reduction gives you a big prop, which gives you better efficiency, but you eat an 6% loss in the box… which at 2kW is going to be 120W, ouch… that’s why I don’t like gear boxes. But the torque is very low compared to the Neugart. 6Nm at the prop is 1.2Nm at the input and I’m not sure it’s enough torque to do anything? The Neugart is 40Nm at shaft Nominal vs 6Nm… am I reading it right? If I am I think the Neugart handles 7x more power.

You have to differ: SSS has max ~2Nm input @max 25kRPM, so after gearbox: 10Nm @5kRPM
The 6374 has about 6Nm input @max 7,5kRPM, so after gearbox: 30Nm @1,5kRPM.
Look for props with ~0,8kRPM - 1,5kRPM rating. e.g. a solas 14"x19" is rated for 3,25kRPM max efficiency. And I don’t think you want to go higher than 14" diameter…most ppl here don’t want to go beyond 7" diameter…

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I did some tests with the nema 23. On the first static tests the gear was broken after about 20 seconds. For the second test I added 3 needle bearings. I ran the prop system several minutes at full load underwater. The motor was running at 4kw @ 44 volt. I could not find any damage after diassembly Maybe the nema is an good option with a bit work on it. The only thing I saw is that you need about 100 to 150w only for the gear. Depending on temperature. But even without load this thing gets hot really quick. I will make a post with my whole setup soon.