Suggestions for a decent drum

[robusto]

Re: Suggestions for a decent drum

For reasons known only to themselves, Ford elecric window winders have a limited life (Im onto my 3rd or 4th).

The part that breaks down is unrelated to the actual 12v dc motor.

So I have plenty of these sturdy little motors available , and have utilised one in my barbecue roaster.

Its powered by a 1 amp transformer which I use to control the speed: 12 volt (too fast) 9 volt (still too fast) 6 volt --ideal: 45 rpm.

These motors have lots of torque. Four hundred grams of beans plus rotisserie and drum weight are no challenge.

Although they were designed for short burst winding windows, they have no trouble doing roasts up to 15 minutes. The lesser voltage probably helps in this regard.

Ill post some pix soon


Robusto

[AndyCJ]

Re: Suggestions for a decent drum

nunu - I reacon a windscreen wiper motor would drive that round at a better RPM, they mostly have 2 settings, normal wiping, and fast. So if you decide to enclose the drum then you can speed it up too. Just an idea? You could pick one up for round $10, and they run off a 12v battery - which you can pick one up from a mechanic (dead one) thatll still run the motor for nix (all you need is a battery charger)

[nunu]

Re: Suggestions for a decent drum

This one is mains powered. Im half tempted to open the thing up to have a little peek.

Regardless, my biggest concern at the moment is if I add more holes, will it be counter-productive, i.e. will the beans be exposed to too much heat in points, and burn in spots. I do have some temp control with the burner, but it doesnt look like theres much difference between low and full whack.

[Dimal]

Re: Suggestions for a decent drum

Hi again nunu,

Im not really up with the technical specs of your everyday roast spit motor... Is yours powered via connection to a 12V Battery or direct to the mains? If it is battery powered, maybe you could get yourself a dual voltage battery charger, 12/24 Volts with sufficient grunt to drive the spit motor.

If mains powered, the options become more difficult :-?, e.g. you may have to consider a pulley drive system... bigger pulley on motor, smaller pulley on drum; could be feasible but a bit of mucking around.

Mal.

[nunu]

Re: Suggestions for a decent drum

I dont think many rotisserie motors are much more than 4 rpm. Im not looking at particle acceleration, just a tiny bit faster.

Even my cordless drill is a bit fast. 20 rpm would probably be as fast as I want/need to go.

[Boris]

Re: Suggestions for a decent drum

Good luck with the speed control. I had a look a the spit rotisseries, non of the sellers could tell me the RPM. I ended up going with a cordless variable speed drill ( had it already). It was alot more sensitive than the variable power drill which wanted to atomise them even on the lowest setting. I put an adjustable clamp on the trigger to set the speed.

Boris

[Dimal]

Re: Suggestions for a decent drum

Great job nunu [smiley=thumbsup.gif],

Youve certainly got the heart of the roaster worked out, fine-tuning will be a bit of fun ,

Mal.

[nunu]

Re: Suggestions for a decent drum

If you look closely at the drum, you can see the heads of the bolts. The drum has a total of 21 1/4" bolts fixed with nuts. They are aligned in diagonal rows of 3.

It was a fairly expensive exercise, as the only readily available parts were the wood that I attached the spit hardware to, and the lid from the stainless steel rubbish bin. Everything else I purchased.

Another thing on my to-do list is to try to speed up the motor for more agitation.

[Framey]

Re: Suggestions for a decent drum

Geez nunu, youre making me look bad. Ive been trying to tack together a roaster for months now and you pull one together overnight

Nice work. Did you go with bolts for agitation?

[nunu]

Re: Suggestions for a decent drum

At least its shiny.

With regards to holes, the biggest thing Im worried about is burning the beans. More holes = more exposure the the flame from the burner. With the few holes that I have, Im getting some beans that are spotted from exposure to the heat. I can easily drill some more holes in the drum. Holding heat in isnt an issue, as the hot air inside the drum is what Im trying to keep in. A bit of a shroud between the drum and burner to keep heat directed to the drum might be a future upgrade.

Currently, the roast finishes in ~20-25 minutes for 300g. I was messing around with the intensity of the burner, as well as placement (not directly underneath), so this figure might be a bit high. Ill keep testing, as I really want this roaster to do 500g batches at least.

[Boris]

Re: Suggestions for a decent drum

Nunu,
Its a work of art. I love things people come up with in their back yard, its the Mc Giver gene, some people have some dont. If I might suggest, me thinks you might be baking more than roasting. Those holes to let hot air in really dont look sufficient, but then Im only a gas turbine specialist and would really know. (might explain the uneveness yoiu mention.

I can see you dont want the holes too big, the beans will fall out. Can you permanently fix SS mesh to the inside, that way your holes could be bigger. ;D Even a something like a shroud over the top of the drum to help concentrate the heat over the top of the drum might make it a little more energy efficient.

2 bobs worth

Boris

[nunu]

found a decent drum!

This photo shows the clearance between the drum and burner.

[nunu]

found a decent drum!

This picture shows the lid/top of the drum. I inverted the bin lid sp there wouldnt be any snags during removal. Also note the prongs securing the lid to the drum. The thumbscrew is only finger tight, to allow easy removal for dumping.

[nunu]

found a decent drum!

This is the bottom of the bowl/drum. The thumbscrew is very tight, to keep the drum from sliding along the shaft.

[nunu]

found a decent drum!

Heres a side on view of the roaster.