Suggestions for a decent drum

[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.

[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.

[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

[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.

[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

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.

[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)

[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

[nunu]

Re: Suggestions for a decent drum

Ive drilled holed in the ends of the drum. Im still wary of drilling more holes in the side of the drum because of the exposure to an open flame. Im just afraid of wasting beans if I make a mistake :P

[nunu]

Re: Suggestions for a decent drum

I took the plunge and drilled heaps of holes around the drum. I also fashioned a heat shroud between the burner and the drum, forcing the heat in the direction I want it to go, not out the sides.

Ive noticed that there is an issue with unevenness. The unevenness is much more pronounced at larger batch sizes. So now Im looking for the optimal batch size. It lies somewhere between 300-500g.

Ill post some more pics soon.

[nunu]

Re: Suggestions for a decent drum

As an experiment, I took my other drum (which didnt have as many holes in it) and drilled the existing holes bigger, and added bolts and nuts. The thing looks like a medeival mace with all the studs. The only holes are in the lid (sadly I only have one lid), at least the smoke has somewhere to go still. I also can see how the beans are going through the holes.

Did a test roast with the newly made solid drum and I like the results. No spots on the beans (from direct exposure to the heat from the open flame), and just a tiny bit of unevenness (this is more than likely attributed to the lack of speed from the motor). Batch size was 300g and could be increased with a faster motor speed. First crack took place at 12:15, and 2nd followed at 17:00. I stopped the roast at 17:15 and cooled.

I think I may have things sorted out. The results are satisfactory at present, but a faster motor would surely produce improved batches. If a wiper motor just happens to land in my front yard sometime, Ill make the change, but as it stands, No changes are needed.

Camera batteries are flat, so Ill have to charge the batteries and take some photos.

[Dimal]

Re: Suggestions for a decent drum

Hi nunu,

Sure sounds like youve got the roast duration and timings very close to spot-on. From what others have posted, it might be best to try and find a suitable Windscreen Wiper Motor instead of the genuine spit roast motor youve got. This should then give you the sort of rotation speed youre looking for and easier control to fine-tune the speed if necessary. Should be easy to get one from a local wrecker for next to nix :P,

Cheers,
Mal.

[robusto]

Re: Suggestions for a decent drum

Second that. The motors which come with store-bought rotisseries are a tad too slow.

A windscreen motor would have better speed and power. Speed can be slowed if necessary with a cheap trim pot from Dick Smith or Jaycar.

RObusto

[nunu]

Re: Suggestions for a decent drum

Re: wiper motor, Im under surveillance atm, so it might be just a bit hard to run and get one. Seems the Minister of Finance is conducting an inquiry into the particulars of this roaster project. R&D isnt really on the approved list for the budget.

Time to do some lobbying! :P

[nunu]

Re: Suggestions for a decent drum

As promised, here are the pics of the semi-solid drum roaster.