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One pound pumper
By golly, it works!! May not have time to fully flesh this out before contest end, but it should offer some amusement ... built this over the past week

Working/design capacity: 1lb
Heat source(s): electric
Agitation: air (spouting bed)
Roasting time to full city: 8 minutes + (variac controlled)
Max temp: 470F - nominal air flow, ~80% power

The system uses two 15A circuits.

- heat gun cartridge - 8.7A (low)/12.7A (high)
- pumper element on 10A variac; 9.5A maximum draw
wet/dry vacuum on 2.25A variac; draws 2.25A@90V


- slip the pumper on to the air manifold
- load the beans (i use a canning funnel)
- turn on the blower, increase the voltage until you see good circulation (~80V)
- turn preheat on at low power
- turn the pumper element on at about half power
- tweak the blower/heater variacs to keep the beans from going ballistic, while maintaining the desired ramp rate.
- turn off both heaters when you reach your target roast; crank up the air flow a bit.
- when cool (takes ~3minutes to ambient), pick up the pumper - trying not to kink power or thermometer cables - & pour the roast coffee into your container.
scotthal attached the following image:

Edited by scotthal on 07/31/2007 10:39 PM
Food for thought; coffee for concentration
Tools & implements of reconstruction:

Dremel w/cutting wheel, router bit
Tin snips

Parts list, approximate cost:

2nd generation pumper - $2 (thrift)
large bake-a-round pyrex bread tube - $3 (thrift)
silicon baking mat - $14 (amazon)
4.5"x15" aluminum flashing - ?? (shop scrap)
4" hose clamps (2) - $2 (lowes)
RTV (optional)
Total (this phase): $21


I cut the original pumper's chamber into two parts - trim ring & funnel - using my dremel. Routed out the trim ring to loosely fit the pyrex tube, and ground the funnel to slide into the tube.

I then bolted the funnel to the heater housing (small screws, lockwashers, loctite), laid down a cushion of RTV where the glass would rest, & let it cure.

The pyrex tube was then set in place and the assembly secured by wrapping it with a strip of baking mat, aluminum flashing, & hose clamps. Note: the silicon mat extends slightly above the height of the funnel, & gets compressed by the trim ring.
scotthal attached the following image:
roast chamber[370].jpg

Food for thought; coffee for concentration
That's what we are looking for! Originality. A new look at an old system.

Is it performing to "Design capacity"??

Didn't take any photos of this step; just bypassed the thermal fuse and thermostat. Clipped the rivet joining thermal fuse & power feed to free the eyelet/lug; moved it to the copper post remaining after i crunched the thermostat base.
Food for thought; coffee for concentration
Ummm. You don't think i actually kept that wimpy fan? I cut it out, cleaned up the hole, and inserted a slip fit coupler of sorts munged out of kitchen sink (1.5") plumbing.


6" tailpiece - $2 (A-Boy)
6" extension - $4 (Lowes)
1.5":1.25" nut - $2 (Lowes)
1.5" hose clamp - ?$0.50
Total (this phase) - $8.50


From the top (threaded end) of the extension tube - i cut above the flare; cut (& split) the next 2" chunk, and discarded the remainder.

I then cut & split the shoulder end of the tailpiece - not sure as to the exact dimension, but i wanted it to be wide enough for the hose clamp, and short enough that the cut end of the extension tube protrudes slightly.

Photos should be relatively clear as to the desired result
scotthal attached the following image:
lower housing[371].jpg

Edited by scotthal on 07/31/2007 10:12 PM
Food for thought; coffee for concentration
Relatively simple - punched a hole in the bottom of the housing; added some aluminum flashing as a heat diverter/diffuser - i used pop rivets to secure it. Wanted to make sure that any hot air escaping the lower housing didn't melt the thermoplastic.
scotthal attached the following image:

Food for thought; coffee for concentration
So what are you using as a fan/blower?
Parts list, approximate cost:

Heat gun guts - $10 (Harbor Freight, on sale)
Kitchen sink P-trap - $9 (Lowes)
4" kitchen sink tailpiece - $2 (A-Boy)
1.5" hose clamp - $0.50
2-gallon wet/dry vacuum - $15 (Sears, on sale)
2" split sleeve - scrap from lower chamber assembly
Total, this phase: $38.50


Unwrap ~1.5 layers of the insulation so that it fits in the tailpiece; cut to length. Trim the plastic flange on the heater core to the same diameter as that on the tailpiece, and slide it into place.
scotthal attached the following image:

Edited by scotthal on 07/31/2007 10:15 PM
Food for thought; coffee for concentration
The sleeve and hard rubber gasket serve as a stop for the pumper; wiring is fed through the tube sidewall, which is sealed with duct tape. The assembly gets lashed (using wire ties) to a convenient vertical surface.
scotthal attached the following image:

Food for thought; coffee for concentration
The threat to the thermometer cable is actually quite small; it's 3ft long, sheathed, & very flexible. If it were really a problem, i could just slide the probe out before unloading the beans (it's a slip fit). I haven't had any problems w/component failures thus far; but i have only run 10lbs of green through - i use a modified poppery for most of my day_to_day needs.

I'd expect the heat gun element to be relatively long-lived in this configuration; as it is running at the low setting, high air flow keeps it pretty cool (exit temp <300'F), & it's not subject to mechanical shock - the metro cart it's lashed to is too big to drop or knock over.

Will probably park this rig under 'lessons learned' - i've sketched out a somewhat simpler setup (sans pumper) that should be able to handle 8oz while only requiring a single 20A circuit. Might even be able to run it without the variacs... high/low switch + air flow modulation (via a standard PVC irrigation ball valve).

Relto roast photos - i tend to get involved in the process (as in, 'now where did i put the fire extinguisher?'); but i just took a 1lb batch of Moka Kadir up to a hair short of Vienna (7minutes to first crack, another 5 to second - running _low_ on preheat, & less than 90V on the pumper element). Took a couple shots before the sun set
scotthal attached the following image:

Food for thought; coffee for concentration
Like other designs, this one is a good example of creatively making do with what you have, but by the same token would be a little difficult for others to duplicate.

I like the idea that you removed the heat gun heating element. Very smart. I hope others follow suit. I'm not too keen on the 'plumber's nightmare,' although it deals with piping the heat using what you could find at the hardware store.

The one pound capacity is great!
You know ... I have a love / hate relationship with plumbing, but I believe this would fall into the category of the former. Grin

It is the thought process that truly fascinates me ...
What made you think of taking the heat gun apart and shoving it down the drain? Shock

Great concept and great fluid be batch size! s:2s:2

Eddie Dove

The South Coast Coffee Roaster
vita non est vivere sed valere vita est
Home Coffee Roasting Blog and Reference
Suspect that it stemmed from ye auld idiom 'everything but..."; a neuron misfired, & i had to ask - why not the kitchen sink?
Food for thought; coffee for concentration
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