Roaster Motor?

[wrstikoff]

Re: Roaster Motor?

[QUOTE=Dennis link=1149589545/0#14 date=1180011527]

Hi Framey

I knew I should have paid more attention in Science...or was it Math? So pardon my ignorance here...

Shouldnt the weight of the beans play some part in this equation?

Hey Framey,

The weight of beans dont come into play because their effect of their mass work in two ways. First the more mass of beans the more force they put on the wall the drum due to the rotation of the drum but at the same time because the weight more you need more force to hold them against the wall at the top of the rotation. These forces are the same so the mass doesnt appear in the equation. 8-)

Hope it makes sense.

[Dennis]

Re: Roaster Motor?

Now I remember why I dropped math and science in Yr 11 :-[ - if you had told me it was because it was a matter of economics, or because it was done this way when Tacitus wrote the annals, I would probably understand. :

Im happy to just take your word for it

[Dimal]

Re: Roaster Motor?

These forces are the same so the mass doesnt appear in the equation. 8-)

I dont know that this holds true for all situations wrstikoff. I remember from a few years ago when I worked for a company that ran SAG (Semi-Autogenous Grinding) Mills as their primary ore grinding method, that the mass of ore feeding into the Mill had to be monitored very closely as if the feed into the Mill exceeded a certain critical point, the entire mass within the Mill would Free-Wheel resulting in nothing being ground and the Mill ultimately becoming bogged before the feed conveyor could be stopped in time.

Surely this situation is not dissimilar to the scenario outlined above? :-?

Mal.

[Stew]

Re: Roaster Motor?

These forces are the same so the mass doesnt appear in the equation. 8-)

I dont know that this holds true for all situations wrstikoff. I remember from a few years ago when I worked for a company that ran SAG (Semi-Autogenous Grinding) Mills as their primary ore grinding method, that the mass of ore feeding into the Mill had to be monitored very closely as if the feed into the Mill exceeded a certain critical point, the entire mass within the Mill would Free-Wheel resulting in nothing being ground and the Mill ultimately becoming bogged before the feed conveyor could be stopped in time.

Surely this situation is not dissimilar to the scenario outlined above? :-?

Mal.

Ah yes there is some definite metallugical design here.  The thing about mills is that you are trying to induce energy into the charge and hence break the ore up into smaller bits.  Once the charge in the mill goes above 50% the lever arms starts to help to turn the mill and there isnt enough room to cascade the charge and hence get energy in to break rock.  Here ends the milling dissertation.

Back to roasters - for a good cascading charge (like a mill) you would want to operate at between 70 and 85% critical speed and the formula given above is correct and shouldnt take into account the mass/SG of the bean as it acts on both sides of the force equation.  The big question is do you want you bean charge to cascade as per a mill, roll around the shell or be lifted and then dropped from the top of the shell to the bottom.... there is the important question?

My guess is that a fairly fast cascade would be called for so I would look at say 85% critical speed and make sure that there are some kind of small lifters on the inside shell that will assist in preventing the beans from just sliding around the edge.

But - I am a better mill designer than roaster designer...... for a challenge I think that you should forget drums and go fluid bed!!!

Actually if someone can post a picture of the beans cascading around in a commercial roaster I can compare the charge shape to some pics I have in a text and make a pretty good guess at the % of critical speed.

[Dimal]

Re: Roaster Motor?

Thank you kindly Stew.... Very interesting stuff ,

Mal.

[Framey]

Re: Roaster Motor?

In reply to Ians question about the motor, I cant remember the name of the supplier...  but I reckon I could drive there. Ive only just read this, so if I do some digging I might be able to find the receipt or go for that drive.

Nice to see you here Ian. Ive spoken to you once before at last years CafeBiz. Anyway nice to know youre around and Ill try to find you the source of the motor for you. They were in Cardiff, Newcastle and I was able to specify the motor speed when I made the order.

[Sullo]

Re: Roaster Motor?

So whats the difference effect from flid bed to drum? from what Ive rad tonight, some lean towards drum? but if the drum is heated and the beans are getting air time wouldnt this lend to the same method as a fluid bed? or am I missing something here?
Yes Im another one that shouldve paid atttn at school

tia
Steve

[JavaB]

Re: Roaster Motor?

Steve,

Fluid bed roasters the beans are agitated by the hot air (in effect surrounded by hot air) - they float in the air if you like. All heat is transferred to the beans by the hot air. A popcorn popper is the simplest form of this roasting technique.

In a drum roaster heat is transferred by conduction from the hot drum.... yes there is some air flow but it is much less - primarily carries off the smoke and chaff away from the roasting beans.... some have no forced air movement - just convection..... whilst others have a relatively small volume of forced air flow....

From a recent test the fluid bed seems to produce an more interesting flavour (more elements in the taste) where drum roasting seems smoother and more intense - but not as complex (from a sample of one test- more to follow :).

The best roasters (commercial) are investigating roasting with a mix of both methods.

The Corretto (which I mentioned to you earlier) is kind of a hybrid - and produces excellent roasts. All heat comes into the bowl as hot air from the heatgun..... the air doesnt fully surround the beans and, depending where you aim the gun, some of the heat is passed to the bowl. So hot air roasts the beans as does heat transferred from the bowl - the best of both worlds!!

[Sullo]

Re: Roaster Motor?

thanks for clearing that one up for me JavaB I only just stumbled across this post which has me rethinking a few things and wishing I still had my ducted fan rc jet which I put a turbine motor in, (after much recontruction!) that thing put out an awesome amount of hot air to move the plane thru the air, cant remember how hot it was but was pretty darn hot!
Live and learn!

[wrstikoff]

Re: Roaster Motor?

thanks for clearing that one up for me JavaB I only just stumbled across this post which has me rethinking a few things and wishing I still had my ducted fan rc jet which I put a turbine motor in, (after much recontruction!) that thing put out an awesome amount of hot air to move the plane thru the air, cant remember how hot it was but was pretty darn hot!
Live and learn!

Sullo,

I tried an RC ducted fan at one time. Mine wasnt a hot one though, the plan was to run the air through a heat gun. I found it didnt have enough pressure in the end

[Matt_King]

Re: Roaster Motor?

Maybe this is obvious, but a breadmaker motor would be a pretty good candidate... good speed (120 rpm or so), and heat resistance is a given.

[JavaB]

Re: Roaster Motor?

Maybe this is obvious, but a breadmaker motor would be a pretty good candidate... good speed (120 rpm or so), and heat resistance is a given.

Generally the motor is 1500 RPM with two pulleys for reduction down to 120 RPM.....

But still would be a good idea.... just a little harder to mount as the larger pulley is usually about 100+ mm in diameter and belt tensioning is required etc - plus the motor is open and 240V so you would need to build a box to house it.

[Dimal]

Re: Roaster Motor?

Spot on JB,

At the very least, a cover would have to be manufactured that allows for plenty of ventilation, maybe a cover made from a fine steel mesh? Either way, you need to prevent the likelihood of a little person being able to stick a fine gauge metal rod/skewer/knitting needle, etc into the windings or the connections.... cant imagine anything worse . Also, these motors are only rated for a short duty cycle typically between 12-30 minutes of continuous running then they must be allowed to cool down. Forced air cooling is an option to extend this in the case of motors that fall within the shorter end of the duty cycle.

So, there would be a few things to think about if you want to use one of these motors for this purpose. All the best,

Mal.