Making my drum roaster spin faster?

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Culainn

#1: Post by Culainn »

Hi everyone,

I'm looking to make the drum of my coffee roaster spin faster. It's currently at 64RPM and I want to get it up to 75RPM. This is to reduce my conduction heat transfer and increase my convention

I'm using a Kaldi 400 Wide. Max load is 400g but I load to 300g.

I'm thinking of buying a new motor. Would this make it spin faster? From what I understand if I switch from a 6W to a 15W motor then it will have more power to spin faster. Is this right? Also, my DC transformer has an output of 24V and 3A. So I should be able to power a motor of 82W, right?

Any help would be greatly appreciated.

Culainn

DaveC

#2: Post by DaveC »

A more powerful motor won't cause it to spin faster, but if it's a DC motor, applying a higher voltage will..

If your transformer is 24V and 3A, then it will only power a motor of 72W...and this is if the Chinese who made the transformer weren't over optimistic, or rated it at 3A for n minutes etc..

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Culainn (original poster)

#3: Post by Culainn (original poster) »

Thank you for the reply.

I'm currently running a 6w 24v 0.5A DC motor with the 23v 3A transformer previously mentioned.

You're saying that If I increase the DC to let's say 48v with a new transformer then the speed of the motor would increase?

DaveC

#4: Post by DaveC » replying to Culainn »

It will (assuming it's a brushed DC motor and not brushless). 48V might make the magic blue smoke appear, as it's twice the rated voltage....so perhaps be a bit more conservative.

Capuchin Monk

#5: Post by Capuchin Monk »

You don't have to change the motor. Install PWM board like I did with my Kaldi 400. There are other versions available. You can put something like this in a simple plastic box and have the wire hook up to your roaster DC power input so that it's away from the heat source.

User avatar
civ

#6: Post by civ »

Hello:
Culainn wrote: ... make the drum of my coffee roaster spin faster.
... to reduce my conduction heat transfer ...
Making the drum spin faster will increase the centrifugal force (which is not a force but a concept) the beans are subjected to.
The result is that the beans will be pushed harder against the hot wall of the drum.
This seems to be the opposite of what you want to achieve.

I expect that your roaster's OEM has already found the right speed for your drum which is directly related to the drum's length and diameter as well as vane design and optimum batch size.

Check this site, it was very useful to me:
http://coffeenavigated.net/roasting-coffee/


Image/text courtesy of coffeenavigated.net

And these other ones:

https://paradoxroasters.com/news/heat-t ... n-balance/
https://paradoxroasters.com/news/heat-t ... lance-pt2/
https://shopcoffeeroasters.com/learn-to ... rum-speed/

You can also look for mods other roasters have made to this same roaster.

Bear in mind that two same model roasters from the same OEM may not necessarily behave in the same manner.

Best,

CIV

User avatar
cafeIKE
Supporter ★

#7: Post by cafeIKE »

Why not profile the heat input as do professional roasters?

I've never had a gas roaster, but it worked a treat on electric.

Years ago I had a yacht with a propane furnace. It was powerful, but maintained temperature poorly as the heat input was too extreme. I modified the fan control and gas input to give a nice constant heat.

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Culainn (original poster)

#8: Post by Culainn (original poster) »

Deffo don't want that magic blue smoke!

I'm not sure how to find something between 24v and 48v though as those are standard. It seems like most AC to DC transformers that I've seen for these purposes is either of those.

Is there some device that sits between those two numbers which you'd recommend for this purpose?

Thanks again :-)

Culainn (original poster)

#9: Post by Culainn (original poster) »

Capuchin Monk wrote:You don't have to change the motor. Install PWM board like I did with my Kaldi 400. There are other versions available. You can put something like this in a simple plastic box and have the wire hook up to your roaster DC power input so that it's away from the heat source.

OMG IT"S YOU!!! lol

So I literally copied what you did with the PWM board. In fact your alteration was my inspiration (and a bit of feedback from a course I'm doing at the moment)

However, I've found that on max with the PWM my motor only goes as fast as 64RPM (I counted). How did you manage to make the motor spin faster? I can only make it spin slower.

Thank you for the reply :-)

Culainn (original poster)

#10: Post by Culainn (original poster) »

DaveC wrote:It will (assuming it's a brushed DC motor and not brushless). 48V might make the magic blue smoke appear, as it's twice the rated voltage....so perhaps be a bit more conservative.
Deffo don't want that magic blue smoke!

I'm not sure how to find something between 24v and 48v though as those are standard. It seems like most AC to DC transformers that I've seen for these purposes is either of those.

Is there some device that sits between those two numbers which you'd recommend for this purpose?

Thanks again :-)