Low-cost DIY caning/spanking machine

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Re: Low-cost DIY caning/spanking machine

Postby OrgasmAlley » 07 Oct 2021, 20:49

As I'm working today, an easy way to put the above stepper's torque in context came up. Bodine -- top notch US industrial motor manufacturer -- makes a 1/12th HP PMDC motor model 6166 that I use on several smaller sex machines. This motor is rated 130 VDC and 0.74A, or 96 watts, with an output torque of 20 in-lbs (after reduction drive). In comparison, the 425 oz-in peak pullout torque rating is 26.5 in-lbs.
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Re: Low-cost DIY caning/spanking machine

Postby Onwrikbaar » 08 Oct 2021, 10:28

OrgasmAlley wrote:The stepper delivers its peak torque shortly after starting, and maintains a high level of torque through around 500 RPM, while the (presumably brushed) drill motor starts at its peak and falls off directly with speed.

The latter does not seem to be the case. With the (heavy Delrin) cane I use, the force of the impact is significantly greater after a 270° swing than it is after a swing of 180°. This suggests that my motor keeps accelerating all through the swing.

I will still maintain that my setup can get similar output.

With very light implements, possibly. With more mass attached, probably not. Going by my experience with NEMA23s, a caning machine based on one can undoubtedly be built, but I suspect it will be somewhat disappointing - dependent on one's wishes and expectations, of course.

AccelStepper is a solid library

As far as I recall the AccelStepper and FastAccelStepper libs don't do stall detection (but please correct me if I'm wrong, it's been a while). This means that you need some kind of sensor or limit switch to detect the (in practice slightly varying) target position to be able to stop/reverse the motor on impact. In that respect the setup with a brushed DC motor is simpler too.

Anyway, I would be delighted to see different implementations of caning/spanking machines, so we can compare hardware & software complexity and performance in the real world, rather than theorize about it - and perhaps come up with a reliable "reference design" that most hobbyists can build. Judging by the reactions I get on Discord, there is plenty of interest :D
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Re: Low-cost DIY caning/spanking machine

Postby OrgasmAlley » 08 Oct 2021, 13:20

Onwrikbaar wrote:The latter does not seem to be the case. With the (heavy Delrin) cane I use, the force of the impact is significantly greater after a 270° swing than it is after a swing of 180°. This suggests that my motor keeps accelerating all through the swing.


Certainly it keeps accelerating... no claim that the torque falls to zero after the motor is moving, just that it's peak is right at the start and it falls directly thereafter. There is no point at which torque drops to 0, until the magic smoke comes out. A PDMC motor's torque is at its maximum when first starting, and falls in a linear inverse proportion to speed.

The contrast I'm pointing out is that the torque curve of a stepper motor -- which starts with a hump such that it remains high from say 0-400 or 500 RPM, before falling steeply -- is an advantage in an application of slow speed acceleration like this one. A stepper will apply more of its rated torque over this stroke than a PMDC motor. I apologize if that wasn't clear.

With very light implements, possibly. With more mass attached, probably not. Going by my experience with NEMA23s, a caning machine based on one can undoubtedly be built, but I suspect it will be somewhat disappointing - dependent on one's wishes and expectations, of course.


In my scope, with the Spank-O-Matic implements topping out with the Oak Fraternity Paddle at something like 4 pounds, everything one would use with this type of machine is very light. I referenced a NEMA23 motor with torque rating 30% higher than a high quality 96 watt PMDC motor. It's plenty strong to swing the light implement you've shown. One can definitely find NEMA23 motors that cannot... a quick look found a 5718 series Nema23 stepper rated at 64 oz-in, so there is a huge range. No claim that _every_ NEMA23 is sufficiently capable.

As far as I recall the AccelStepper and FastAccelStepper libs don't do stall detection (but please correct me if I'm wrong, it's been a while). This means that you need some kind of sensor or limit switch to detect the (in practice slightly varying) target position to be able to stop/reverse the motor on impact. In that respect the setup with a brushed DC motor is simpler too.


You're right about AccelStepper, but that doesn't mean you "need" a sensor or limit switch. You could implement this as simply as manually moving the cane until it's against the target and retracting a known rotation, then accelerating for that rotation and holding. This obviously doesn't account for lost steps... one would need to remain within the motor's capability. Or you could intentionally overrun the target with extra steps that fail and are ignored. No harm to the stepper.

I'd definitely agree that it's superior to use either a limit switch to set contact with the target or a more capable closed loop stepper, but not necessary. I also agree that your drive approach is as simple to implement as possible, so everything I'm offering is a more complex alternative.

Anyway, I would be delighted to see different implementations of caning/spanking machines, so we can compare hardware & software complexity and performance in the real world, rather than theorize about it - and perhaps come up with a reliable "reference design" that most hobbyists can build. Judging by the reactions I get on Discord, there is plenty of interest :D


Sorry if it wasn't clear... I'm talking from experience, not theory. My actual dev target was a whipping machine, from shoelace (think the Pain4Fem machine) to short singletail... in this task, the detailed control over acceleration that the stepper provides was vital. You can swing a shoelace with a spring drive or a bare motor with voltage control, but when you ALSO want to attach something with a different combination of mass, length, and air resistance it requires a different acceleration profile. Life, work, and loss of interest shelved the project. I'll probably get back to it at some future point.

An aside... I also experimented briefly with an articulated arm on the SOM pneumatic system, which has quite detailed control over acceleration . The issue with a flexible implement on the SOM is the abrupt, short arc of acceleration, and with a mechanical arm/elbow I was able to get about 230 degrees. This worked pretty well... but the result with more complex than desirable and I ended up considering it an amusing side project.
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Re: Low-cost DIY caning/spanking machine

Postby Riddle » 09 Oct 2021, 09:54

Is it possible to purchase a new electric motor with gear-reduction for this project?

https://www.amazon.com/Greartisan-Elect ... RydWU&th=1

Would this motor work? Which RPM would be best?
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Re: Low-cost DIY caning/spanking machine

Postby kinbaku » 09 Oct 2021, 11:41

Riddle wrote:Is it possible to purchase a new electric motor with gear-reduction for this project?

https://www.amazon.com/Greartisan-Elect ... RydWU&th=1

Would this motor work? Which RPM would be best?

Can harm this motor for the short time of contact: "4.Overload: As far as possible within the specified load range, prohibit motor blocking or close to the stall state for too long time to runs. Otherwise, the motor will burn out." ?
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Re: Low-cost DIY caning/spanking machine

Postby Gregovic » 09 Oct 2021, 13:21

When using a stall detection like suggested in the first post I don't think the motor would be stalled long enough for there to be a problem. DC motors don't really like being stalled for extended time as heat builds up in the coils that can't go anywhere. But if that state is detected and corrected within a few milliseconds there isn't really a problem. I suspect that geared motor would work fine if you chose a version with enough speed (so probably a 500 or 600 RPM version would be my guess, but maybe someone with more experience can chime in)
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Re: Low-cost DIY caning/spanking machine

Postby Onwrikbaar » 09 Oct 2021, 17:58

Riddle wrote:Is it possible to purchase a new electric motor with gear-reduction for this project?

https://www.amazon.com/Greartisan-Elect ... RydWU&th=1

Would this motor work? Which RPM would be best?

That one will probably not do the job. It is rated at 12V and 0.6A, so only 7.2W.
Also, 20 rpm is quite slow for a cane. It may be enough for a heavy paddle, but this motor doesn't have the torque required for that.
I still need to measure the speed of my setup, but I estimate that it does a full rotation in under half a second. That would be 120 rpm. I'll post the exact number when I have a bit more time to work on the code again.
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Re: Low-cost DIY caning/spanking machine

Postby Riddle » 10 Oct 2021, 07:05

Onwrikbaar wrote:
Riddle wrote:Is it possible to purchase a new electric motor with gear-reduction for this project?

https://www.amazon.com/Greartisan-Elect ... RydWU&th=1

Would this motor work? Which RPM would be best?

That one will probably not do the job. It is rated at 12V and 0.6A, so only 7.2W.
Also, 20 rpm is quite slow for a cane. It may be enough for a heavy paddle, but this motor doesn't have the torque required for that.
I still need to measure the speed of my setup, but I estimate that it does a full rotation in under half a second. That would be 120 rpm. I'll post the exact number when I have a bit more time to work on the code again.

Thank you for the information. I did forget to look at the wattage.

I am curious about how a 60W, 158rpm, 24VDC motor would perform.
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Re: Low-cost DIY caning/spanking machine

Postby OrgasmAlley » 10 Oct 2021, 14:30

A typical single speed "drill/driver" will have RPM in the 600-1000 range. A two-speed version probably has slow speed of 300-500 and high speed more like 1500-2000 RPM. Onwrikbaar, do you know what your donor drill was? If it's a common model, both speed range(s) and torque should be available data. Using a drill or drill/driver has advantages... cheap, durable, and a chuck to easily mount an implement.

If 180 degrees of rotation takes 1/2 second, that would imply a rotational speed at the end of the stroke of 240 RPM because it's starting from 0. However, unless the motor is quite powerful or the implement quite light, I wouldn't expect to reach the motor's top speed in 1/2 rotation. I'd start with around 500 RPM and at least 8-10 in-lbs torque, as a ballpark (to be clear, I have not tested PMDC motors in this application, and that's theoretical... but I have spent 20 years building kinky things with motors commercially).
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Re: Low-cost DIY caning/spanking machine

Postby Onwrikbaar » 10 Oct 2021, 17:28

OrgasmAlley wrote:A typical single speed "drill/driver" will have RPM in the 600-1000 range. A two-speed version probably has slow speed of 300-500 and high speed more like 1500-2000 RPM. Onwrikbaar, do you know what your donor drill was? If it's a common model, both speed range(s) and torque should be available data. Using a drill or drill/driver has advantages... cheap, durable, and a chuck to easily mount an implement.

It looked exactly like the one in the photo below, except the batteries it came with are 18V. "Land Goed" is a brand carried by an agricultural supplier, not the original manufacturer. I got it off a second hand site for €5, without a case or any kind of documentation or specifications. If I power it from 18V with no PWM in-between, and driving a heavy cane, the motor on startup trips my 10A lab supply's overcurrent protection :)

1c.jpg

If 180 degrees of rotation takes 1/2 second, that would imply a rotational speed at the end of the stroke of 240 RPM because it's starting from 0. However, unless the motor is quite powerful or the implement quite light, I wouldn't expect to reach the motor's top speed in 1/2 rotation. I'd start with around 500 RPM and at least 8-10 in-lbs torque, as a ballpark

It is entirely possible that I underestimate the time a rotation takes. I will measure it in software, with the heavy Delrin cane as used in my Youtube clip, as soon as I find a bit of time to do the programming. I have some electronics to finish for a client first.
I have spent 20 years building kinky things with motors commercially.

Your motorized sex machines look extremely sturdy and well-designed!
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Re: Low-cost DIY caning/spanking machine

Postby Onwrikbaar » 10 Oct 2021, 19:29

Riddle wrote:I am curious about how a 60W, 158rpm, 24VDC motor would perform.

Pretty well, I suspect, especially with light implements.
If it's a brushed motor, you can use the same H-bridge I have - the BTS7960, which can handle up to 27V and 43A.
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Re: Low-cost DIY caning/spanking machine

Postby OrgasmAlley » 11 Oct 2021, 12:59

I can't find any actual information about that drill, but I do assume there's some factory in China spitting internally-identical units out in different housings. It's probably very similar to this drill with the same handle angle from Harbor Freight, a very successful US vendor of cheap tools: https://harborfreight.com/18v-cordless- ... 62873.html

No torque is provided. Single speed, 0-900 RPM.
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Re: Low-cost DIY caning/spanking machine

Postby OrgasmAlley » 11 Oct 2021, 18:32

Onwrikbaar wrote:Your motorized sex machines look extremely sturdy and well-designed!


Thanks!
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