Rick Hughes wrote:
"Bob Minchin" wrote in message
...
Bob ... very interested in this ... have you made a set of drawings
for this ? ...... (or is that being to cheeky)
Not at all cheeky just naive! LOL
The con rod was made the same way as the arms but longer. same 35mm
bearings. Bought a pack of 10 off fleabay - stupidly cheap.
Even the pillow blocks for the crankshaft were less than a fiver each.
Bob ... thanks for that, the crank seems to be the biggest troublesome
item .... wood work side no problem, but I no longer have access to a
lathe.
I'm assuming the somewhat complex motor arrangement was just to use what
you had ? ...
A suitable 1/2 hp 1ph induction should do the job, key would be getting
toothed belt step down ratio correct.
Thinking here that a cement mixer motor would have enough ooomph.
Or do you find variable speed is needed ?
Did you get the bearing supports of ebay as well ? ..
Hi Rick,
The most common motors are 4 pole 1425 rpm. I found that a crankshaft
speed of 230 is rpm seems about right. so that means more than 6:1 speed
reduction. Vee belt would need at least 2" pulley for the motor to get a
good grip for the belt and then a 12-13" driven pulley!!
I opted for toothed belt drive for grip but 22 was the smallest pulley
that would fit my motor and would need about 135 teeth - blooming
expensive. My 72 tooth was the dearest item I had to buy from RS even
with trade discount.
If you can find a 6 pole (950 rpm) or even an 8 pole (720 rpm) this will
help a lot.
Yes I just happened to have a 3 phase motor and an inverter as I collect
such things when I see them free/cheap on the bay.
Once I got the speed right, I've not needed to change it but the
inverter does give me a soft start over 5 seconds so i can load up the
sieve and then switch on (starting loaded without a soft start might be
a bit vicious)but I suppose i could always start empty and load once it
was running.
Using the variable speed and the adjustable throw crank just meant I did
not have to get everything spot on.
Yes the pillow blocks can from ebay. Joanne at JBenterprises (or
something like that) will sort you out for those.
http://myworld.ebay.co.uk/779joanne.
HTH
Bob