Thread: Draco Solum 16 drum motor failure

Well it finally happened - my motor that has been going reliably since 2020ish has finally decided to die.

Email to Draco.. waiting a response.

I may be tempted to design and make a gearbox that allows the motor to be housed outside but retains the slip gear mechanism using a weight inside where the motor acted like the weight before.

Sorry to hear that , Nick . I have the same drum , and remember reading your post about the installation .

Draco are usually pretty good at responding to such issues , so hopefully you wont be down for too long . At least it happened when the water is cooler !

I robbed this off a post someone else put together regarding the draco drum motor. The Original post will probably be on the forum somewhere:


Draco Drum motor spares.

Part no. 17HS19-1684S-PG19
Description
This Nema 17 stepper motor with 48mm body and 1.68A rated current, integrated a planetary gearbox of 19.19:1 gear ratio. It's a good solution to applications that with limited space but need low speed and/or high torque.

Electrical Specification
Manufacturer Part Number: 17HS19-1684S-PG19
Motor Type: Bipolar Stepper
Step Angle: 0.094deg
Holding Torque without Gearbox: 52Ncm(73.6oz.in)
Rated Current/phase: 1.68A
Phase Resistance: 1.8ohms
Inductance: 3.2mH ± 20%(1KHz)
Gearbox Specifications
Gearbox Type: Planetary
Gear Ratio: 19.203:1
Efficiency: 80%
Backlash at No-load: <=3deg
Max.Permissible Torque: 3Nm(424.83oz.in)
Moment Permissible Torque: 5Nm(708.06oz.in)
Shaft Maximum Axial Load: 50N
Shaft Maximum Radial Load: 100N
Physical Specifications
Frame Size: 42 x 42mm
Motor Length: 48mm
Gearbox Length: 35mm
Shaft Diameter: Φ8mm
Shaft Length: 20mm
D-cut Length: 15mm
Number of Leads: 4
Lead Length: 500mm
Weight: 560g



The Motor is often a Nema 17 stepper with 19 to 1 reduction gearbox which is about £25 https://www.omc-stepperonline.com/ne...s19-1684s-pg19

The seal kit for the end of the motor is something like a PS1000 seal which is £7 I didn't check the sizes though. https://www.poolandspacentre.co.uk/p...yword=&vt_camp aign=1684349664&vt_adgroup=67326337804&vt_loc_inte rest=&vt_physical=1006716&vt_matchtype=&vt_network =g&vt_placement=&gad_source=1&gclid=CjwKCAiAqY6tB h AtEiwAHeRopRFmoomMtekwmQZ8y_ejBNxywatdd1kQeG8W3Ek3 2_4CUH-U6zZIJBoCnGMQAvD_BwE

It was the seal which stalled the motor on mine. I just took the seal kit out. Polished the Nylon up. Put some clear silicone grease in it and reassembled.
If you have any problem with the stepper driver/ controller board thats actually a Draco item but there are other driver/ controllers out there.
I should have taken some pics really but the assembly is:

Nema17 motor and reduction gearbox. From the motor gearbox shaft there is a white nylon shaft attached by a grub screw. This is the shaft the cog is attached to. The nylon shaft passes through a PS-1000 style seal to prevent water ingress into the motor housing.

The motor housing is just a piece of pressure pipe glued into the black oval shaped plate that you can swing up to disengage the cog when it's all fitted in the filter. I just pulled mine apart to expose the motor.

To get mine going again I polished up the nylon shaft as it was a bit rough to be honest with tooling artifacts from being turned in a lathe. I also polished inside of the black nylon laminated section that the water seal goes through. This was just a cut hole which a couple of rubber seals run against. Again the hole has been cut by a cnc router and slightly rough. I reassembled with silicone grease and all is good again.

Having said that I don't know how long it will last as there is obviously a reason that Draco have moved away from this setup. I think if it fails again I will just fit a standard geared motor rather than a stepper, and mount the motor outside of the filter with a shaft running through to the drum.

Here is original thread:

https://www.koiforum.uk/koi-carp-cha...ght=Draco+nema

Well Draco do an external conversion kit for 250+GBP!

I think an option here is to build my own. I've still got some stepper choppers around here and have experience building servo systems.

The V = IR means the servo is 1.68*1.8 = 3.024V. This sounds familiar as I have a 3.3V running on 12V using a. micro-stepper current chopper that with a 50:1 planetary gearbox puts out a horrific amount of torque for telescope focusing (it means it has a lot of photography kit hanging off it). With the chopper it works really well for fine focusing and stays completely cold even with 12V.

I assume the main controller uses a servo controller todo the same or there's one in the little box.

I'll get the motor housing and check it tomorrow.

It will be interesting to see what you figure out.

So I've pulled apart the motor assembly, the stepper-gearbox assembly.

1. Water and condensation inside the plastic tube of the motor assembly
2. Water had progressed into the gearbox seal section
3. Water in the gearbox (it sound rough but with the stepper it turns but there's dirt/gunk/grease in the gearbox)
4. One of the stepper end screws is rusted
5. The stepper motor itself (without the gearbox) is siezed solid and can't be turned, even with pliers on the stepper shaft gear.

The motor is a stepper+planetary gearbox: 17HS19-1684S-PG19

Given the mode of failure I would be tempted to mount the replacement outside.

The small module inside the little box seems to take power in and has a speed control this means it has a pulse generator onboard that small board hence providing the motor turning by pulsing the stepper poles alternately.

I don't know if it's dumb (ie still continues to attempt to turn the stepper with pulses if there's large amounts of back EMF indicating a problem turning).

The stepper will be a relatively straight forward change. The option here is I could replace the control box completely with a new one and open source the design and coding.

Fastest option is to get a new stepper, add a hole. and put that in but this will not have the slip gear mechanism so either I make an armature like the previous one or make the stepper motor back off and finally give up. The option here is to use a reed switch and magnet in one of the teeth to measure the time it takes to rotate if it slows then system knows there's a problem - it should see that if there's a gear or a drum problem.
The beauty of having an open source ardinio style controller is that people can then adjust it or improve it.

For now I'll order something compatible with the stepper controller (current and voltage) then that can go on the outside.

Pulling the stepper apart the centre magnet usually runs very close to the pole 'combs' but in this case the centre has green corrosion and it looks like the centre poles are corroded onto the outer, I'd also suspect that it's shorted due to moisture and welded itself together.

IMG_4072.jpgIMG_4069.jpgIMG_4071.jpegIMG_4068.jpg

So as you can see - gearbox full of mess, stepper full of mess, so that's a write off.

So my thinking is simple. It's not really a precision engineering system (although the rotation is counted by the number of pulses).

Something like this bevelled 90 gearbox on the onside:
51n3d6TL4gL._AC_UF894,1000_QL80_.jpg

The existing brass rod can then be used for the existing plastic gear, but the rod for the wheel is supported on both ends so it won't bend. The new gearbox and stepper are then connected using a simple shaft coupler.

This is a 1:1 gearbox hence cheap, but also open so any water or condensation cannot find its way into the new gearbox or stepper. I could use a worm gear but I don't want the gear box on the same shaft that enters into the drum chamber. A mod could be that a normal sized shaft drives through, that then drives a train of gears on an armature so that it retains its slip gearing.

So stepper -> 19:1 -> 1:1 90 bevel -> through wall -> drive sprocket onto drum.

What does the draco outside solution look like?

Originally Posted by Alburglar

What does the draco outside solution look like?

https://www.dracodrum.com/conversion-options.html

So I'm now considering a 30:1 worm gear NEMA 17 gearbox.

This has both benefits and limitations.

The NEMA17 from experience has very little torque straight out of its stepper without driving at a higher voltage. The existing Draco controller for this has a speed dial so it can speed up the turn rate from the existing rate of turn to cope with a lower geared gearbox (ie higher turns per output turn) but also has a maximum current that aligns to the NEMA 17 output (I've not measured this but it's a like-for-like).

So this means an external gearbox with a NEMA 17 stepper for £30 from china. If the stepper fails I can replace the stepper itself with another and a worm gear is pretty much bomb proof. What I may do is polish the gear teeth because they're normally manufactured a little rough. I may also replace the lube inside.

Part number: 17HS15-1684S-WG40

The output shaft of the gearbox is 7mm and not 8mm so an axle sleeve will be in order. The good news is you can pick those up from rollerskate shops or anywhere.

This means the old brass rod would fit but another option is to get a brass rod and simply shape it with a couple of bearings to keep it steady.

So this is looking like:
* stepper + gearbox = £30
* 10mm brass rod = £22 (B&Q) or cheaper online but careful of leaching of "brass" rather than brass.
* 10mm plastic rod = ~£12 but ends up around ~£20 for a drinking water safe plastic
* 10mm ID bearing = £4 each. x2

Total ~ £70
+ plastic box for stepper protection, reusing the cable from the original stepper and the cable gland.

This allows a plastic rod with the gear to be fed through into the drum chamber. On a good side - with this any bad blockages have a weak link in the plastic rod and the stepper metal to plastic junction. I'll copy the original gear design so if need be I can make another plastic gear.
I may make the shaft-gearbox joint a split with a clip around it, that means under resistance the gearbox spindle can slip.

Many options for that.

This is very interesting for me Nick as I have an old 25 Draco with the internal drive which is still working ok but am thinking of modifying it to an external.
Your price is good and will be watching your progress.
Keep it coming Nick.

Looked at a lot of these have you a link to the stepper and box as I dont really know what I am looking for?

I have seen one from " Skysmotor " from China for just over £30 but there would be postage on top.

I'll order today - it was via stepper online (ie UK sale of Chinese gear).

I've been a little slow due to other distractions.

https://www.omc-stepperonline.com/ne...PKQY4L9qWpkjHD

Is this the one Nick?
Not ordering one yet,wait to see how you get on.

So costs so far (approx):

32 - motor + gearbox + two flexible shaft couplers
22 - postage from china
6 VAT customs

I'll order a perspex/plastic rod once it all gets here.

Getting the rod and bearings is easier.

Originally Posted by john1

https://www.omc-stepperonline.com/ne...PKQY4L9qWpkjHD

Is this the one Nick?
Not ordering one yet,wait to see how you get on.

No.

The original stepper and gearbox is a 19:1 ratio in that format.

The one I've ordered is this: 17HS15-1684S-WG40. I will be mounting it externally then using a plastic rod through a hole to drive the drum.

Let me see how I get on and I'll keep you posted.

Attachment 43514

Took mine apart and it's a 24v one, the system runs 12v so maybe to slow the motor down as it runs at 3200 r/m which is fast.
Nick,the one you have ordered is that 12v as it doesnt say?

Good point I'll double check.

IMG_4149.jpg

The stepper+gearbox arrived. The shaft fits the existing brass rod for the gears which is nice.

I'm not too worry about 12/24V as I can adjust for that if need be. The important thing is the current which is the same at 1.7A. What you normally do is use a controller that has a higher voltage so that stepping overcomes the back EMF.

In the past I've used a 2.8V stepper with 12Vdc with a current chopping controller and it remains completely cold.

The original 17HS19-1684S-PG19 stepper is 2.7V 1.7A (ie NEMA17). This stepper is also a NEMA17 (same resistance and current limit hence 2.7V too) hence will electrically be the same.

Your motor isn't a stepper - it has two leads and not four. Hence I think they switched from a stepper to a 71:1 gearboxed 24V motor to get the same torque. Hence they need RPMs, 3500/71 = 49.296 of the small gear onto the drum. Slowing that down using 12V will also reduce the current and torque which is not needed due to the 71:1.