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Greetings from Jerusalem plus queries
Koffee Kosmo
Please also look into the volume of the roaster
Heat and fan strength has a third wheel
That is volume
You need to balance all three to work in a roaster
And how much that combination can roast in green bean weight

KK
I home roast and I like it
Blog - http://koffeekosm...gspot.com/
Bezzera Strega: Mazzer Robur Grinder: 5 Box hand grinders: Pullman Tamper Convex: (KKTO) Turbo Oven Home Roaster: CONA Glass Rod Syphon: Pyrex Brewer:
 
http://koffeekosmo.com.au
Argaman
KK--
Thanks for pointing the important of volume. But I'm not sure what I can do to change or fiddle with this -- seems like the "box" just is the size that is, and that's it.

Also, now that I can test temperature -- the results of which *seem* to be reasonable -- shouldn't that tell me about the ability of the heaters (1500W) and fan to affect the whole volume of the oven as it already is now?
 
Argaman
OK, well today I popped the lid off to look "under the hood." It looks like the rotisserie motor is very standard, and shouldn't be too hard to replace, while the fan is buried so deep beneath the wiring, I was afraid to dig down far enough to give it a real look.

As far as swapping in a new motor, the stuff I've seen for sale from China -- ebay or aliexpress -- is fixed speed. I can choose a 30 rpm motor, or a 50 rpm motor, but, well, I don't know how I can tell in advance which will be more appropriate.

It's really not so expensive to try one and switch if necessary, but too much of that kind of trial and error seems like asking for trouble (not too mention a pain).

Any thoughts appreciated.
 
renatoa
Links to the motors of choice ?

You should be aware about the power/torque also... going from 3 rpm to 30 rpm, if same motor with different gearbox means 10x less torque !

As a reference, to rotate 100g of beans, in a 10 cm dia cylinder, at 15 rpm, you need a motor with 0.5kgf.cm torque.
More beans, larger drum, faster speed, all led to more torque needed, proportional.
Edited by renatoa on 03/17/2019 3:26 AM
 
Argaman
Great, thanks for the numbers, renatoa.

So the way I calculate it, if I want to roast 200g at a time, and my drum has a diameter of 14 cm, then at 30 rpm that requires about 2.8 kgf.cm, right?

The motor linked here claims to put out only 2.5 kgf.cm at 30 rpm, so maybe I could get the 25 or 20 rpm version -- which give more torque and need less -- so that I could (maybe) roast slightly larger batches.

Does this make sense?

Assuming, of course, that I can ever get this thing working right -- argh!

https://www.ebay....3219559520
 
renatoa
You nailed it right.
Is the original motor inside oven the same format, is KTYZ50 a direct replacement ?

Asking because what I seen so far these ovens have smaller motors, like the microwave ovens turntable motor...
 
Koffee Kosmo
Argaman wrote:

KK--
Thanks for pointing the important of volume. But I'm not sure what I can do to change or fiddle with this -- seems like the "box" just is the size that is, and that's it.

Also, now that I can test temperature -- the results of which *seem* to be reasonable -- shouldn't that tell me about the ability of the heaters (1500W) and fan to affect the whole volume of the oven as it already is now?



The heaters wattage does not equate in heat stubility once the beans are loaded
Firstly the heat needs to fill the volume void then heat the beans
That repeats over and over as the volume area cools at the expense of heating the bean payload

Can you make a false panel to reduce the volume in an area that has no mechanical purpose e.g. the ceiling

And the 50rpm motor should do the trick

KK
I home roast and I like it
Blog - http://koffeekosm...gspot.com/
Bezzera Strega: Mazzer Robur Grinder: 5 Box hand grinders: Pullman Tamper Convex: (KKTO) Turbo Oven Home Roaster: CONA Glass Rod Syphon: Pyrex Brewer:
 
http://koffeekosmo.com.au
Argaman
KK--
Thanks for the info. Frankly, I'm a little intimidated by the re-working I'd need to do to reduce the interior volume. I'd probably have to drill new holes for the heating elements, which right now are near the four corners of the box, if that makes sense.

Regarding the motor speed, I understood from renatoa that the motor I'm looking at would not generate enough torque at 50 rpm. I'll see if there's a stronger one that can do it and still fit into the relevant fixture. I may just have to compromise with a lower rpm -- which is a real improvement no matter what.
 
renatoa
50 rpm could work, not sure how accurate is that table, I know the motor of this size, but other RPM, and should have enough torque even for 330 grams, imo...
 
Argaman
renatoa--

Do you share KK's preference for 50 rpm? If you think that at 50 rpm the 50ktyz can produce enough torque, that would be great.

You're right that the original motor is not precisely the same -- as you said, more of a microwave turntable, 4W -- but the mounting bracket and the rest of the mechanics seem to be a perfect fit for the specs of the 50ktyz. Only exception is that the new motor is about 20 mm deeper, but that shouldn't be too hard to accommodate.
 
renatoa
Tested these motors in 10, 30 and 60 versions.
The difference from 10 to 30 is significant, from 30 to 60 minor.
These mesh drums should not be compared with the real drum roasting, they are only mechanical agitators, the wall don't store nor transfer heat, to require a spot rpm for optimal operation.
I am confident that these mesh drums can work fine even at lower speed, based on experience with one of my past commercial roaster, Diechmann Roestmeister, which performs very fine with 330 grams at 20 rpm.

If the 50KTYZ is not a direct replacement of what you have now, and you must tinker a bit for any motor, maybe the answer is in the next size of these motors, the 60KTYZ line, where probably the 50-60 rpm versions will have enough torque to not worry at all, even at 500 grams.
 
Argaman
renatoa--

Great, thanks for the feedback. My sense is that the 50 will fit very easily, while the 60 will be a huge pain, if I can figure out how to do it at all.

If you think that the 50 rpm version has a good chance of delivering both the torque and the agitation I need, I'd rather give that a shot -- for 10 dollars -- before launching into any more adventurous upgrades.
 
Koffee Kosmo
Just a quick note on the motor specs

All RPM speeds are measured in free spinning tests
The actual speed will be lower under load

KK
I home roast and I like it
Blog - http://koffeekosm...gspot.com/
Bezzera Strega: Mazzer Robur Grinder: 5 Box hand grinders: Pullman Tamper Convex: (KKTO) Turbo Oven Home Roaster: CONA Glass Rod Syphon: Pyrex Brewer:
 
http://koffeekosmo.com.au
Argaman
Good point, KK!

I've ordered the motor -- now the wait until "China" decides it should arrive... :-)
Edited by Argaman on 03/18/2019 9:33 PM
 
Argaman
Hi all--

After a long summer “vacation” break I can finally get back to roasting. Since we had a visit to the US, during which I drank a different roaster’s coffee each week, I guess I can’t really complain. :-)beach

Well, “China” sent the motor along pretty much on time, but getting things to work hasn’t been easy – in fact, has failed.

Wiring.
Both the official guidelines that came the motor, as well as all the diagrams I saw on-line, had the capacitor connected in parallel across both input leads. But this made the motor jittery and spastic, not rotating. But by simply leaving one lead out of the wiring entirely, I got the motor to turn properly, but it took lots of trial-and-error (with emphasis on error). So now it turns, but…

Torque.
The motor turns fine as long as it isn’t under any load. The moment I connect the drum to it, even empty, the motor becomes extremely unhappy: a nice turn or two, jittering spasms, turns backward for a quarter turn, forward for a quarter turn, more jittering, etc. In short, useless. I removed the vanes I had added, since they made the drum rather unbalanced (far more important at 50 rpm than at 2 rpm), but even this lessened weight made no difference. Maybe there’s some awful friction or inefficiency hidden in the mechanical setup, but even if so I can’t figure how to improve it.

Proposal.
I guess I need a different motor, one that produces a fair but more torque. Obviously the first guess is just a lower rpm version of the 50KTYZ – the 15 rpm version would presumably have something like 3 times the torque. Is this enough? I have no idea, but the experiment only costs less than $10 to try. Obviously it would be great if I could get a stronger motor in there – the 68KTYZ puts out more than 3 times the power (ie. torque) at the same rpm – but I doubt that the existing bracket would carry the weight of that motor and I lack confidence in the my ability to fabricate something stronger.

Any thoughts?
 
allenb
Did some research on this. The capacitor appears to be placed across both CW and CCW inputs (red and green motor wires) and which of the two you connect the hot lead to determines rotation direction. Two yellows go to common from your power source,

This may be helpful:
allenb attached the following image:
synchronous_motor.png

Edited by allenb on 09/15/2019 11:45 AM
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Argaman
Thanks, AllenB.
That's exactly the research that I did -- with the capacitor connecting to one of the leads in parallel. But, bizarrely, this didn't work at all. Reversing the "hot lead" also had no effect on the "direction" of rotation -- since there was no rotation.
Like I wrote, only connecting one input through the capacitor, with the other lead simply unconnected, yielded stable rotation. Go figure.
 
allenb
Some questions:

Assuming you are using a non-polarized cap?
What size in microfarads is the cap?
What are you feeding the motor with? 220 single phase (1 hot, 1 neutral) or 220 two phase (each leg hot but out of phase from each other as in USA domestic high voltage, or 120 single phase?
Possibly cap is bad. Have you tested it?
Can you sketch how you have it wired when it won't turn/goes spastic?

Capacitor has to be in the circuit correctly or motor will have very little to no torque.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Argaman
allenb, thanks for your queries -- I'm by no means confident that I know what I'm doing here.

1. The cap does have "NP" printed on it -- that means "non-polarized," right?
2. The cap says 10 microF on it.
3. The feed is 220V and I think it's what you're calling single phase. The live line goes to the inputs, the outputs go to the neutral.
4. Have not tested the cap -- not even sure what I'd need to do.
5. I've attached a sketch of how it's wired. When both 1 and 2 are connected as in the drawing, the motor simply shakes. When I disconnect 2, feeding power only through the capacitor and only to one lead, the motor turns reliably, but seems to lack all but the most minimal torque.

Any thoughts?
Edited by Argaman on 09/19/2019 4:28 AM
 
renatoa
The capacitor value sounds weird, the 60KTYZ 60 RPM motor I am using currently to turn up to 800 grams of greens is fitted with a 0.33uF capacitor, as in allenb pictures.
Never had an issue with some motors of various size: 50(6-10W) - 60(14W) - 68(28W) KTYZ, in the 10-110 RPM range I used so far.
 
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