I don't think I was arguing about anything on a nameplate or doubting anybody's facts - I was asking for clarification on two posts that seemed inconsistent with each other. Thanks for the further input about the housings, though I'm not sure where that fits in with coal berner's post about 25 lb/hr S-20's on Highboys and regular 520's.
I enjoyed your post where you described the ways your family helps with your refurbs. To me, it's very cool both in terms of both the common interest it provides for your family, and the leverage it provides for your expertise, so that more of these units can receive an extended life.
I'm not sure about your reference to "copycats" on the S-20 enhancements you describe. A few years ago there probably was a risk that Matthaus, with his robotics background, would take a shot at souping up EFM stokers, but I'm under the impression he now has plenty to do at LL.
The rest of the people I know of who restore EFM's are only trying to make sure they work as intended. Congrats in advance on any ways you develop to improve that.
OK lets clear this up for the last time
The original AP-520 -1 with the original S-20 had a max feed rate of 8 teeth with Rice coal each tooth is 2.5 lbs per hr
8 teeth feed rate is 20 lbs per hr max when burning buckwheat size the feed rate is 2 lbs per hr 2 x 8 = 16 lbs max or 2lbs
per hr per tooth. Note the early ones like on the highboy used a slip joint on the feed arm to adjust the feed rate at
bottom. Not like the ones later or current that use the adjustment plate at the top above the drum gear.
Both the early 520s and highboys used this making the feed rate 1 to 4 & 4 to 8 teeth feed rate max by losing the bolt on slip joint /slotted joint
The Df 520 's with smaller gear box has a max feed rate of 10 teeth 2.5 lbs per tooth with Rice coal 2.5 x 10=25lbs per hr
with buckwheat size coal the feed rate is 2 lbs per hr per tooth so 2x10 = 20lbs per hr
Look at the last page in manual you will see max feed rate on DF models http://www.efmheating.com/manuals/DF520 ... lation.pdf
Note they change the feed rate from 1 to 10 teeth to 3 to 10 teeth the original manuals states 1 to 10 teeth like my 1986
manual My 1966 manuals shows the feed rate at 1 to 8 teeth feed rate
As for modification done to S-20 to increase feed rate you need a few parts to modify so it can increase the feed rate
to 13 to 14 teeth feed rate Like Scrapper said there is really no need to do this with a 520 boiler but it can be done
because I seen it done . And just not with 520s but also with 350s boilers .
Like scrapper says the pots are 14.5" across standard S-20s with a S-22 pot ash ring add now it is 15.5 " across 1 extra inch
According to Stoker man that extra inch increases the btu's up to a extra 5k in btus.
The 700 pot is 16" across the top like scrapper says However I thought it was 17" maybe he will check and post back
with the 700 pot size and 900 pot size maybe even the 1300 pot size .
As far as Matt goes he has his hands full with Boeing and L.L stoves and besides he is a AA guy anyway.
being this is only his fifth year burning coal and about 4 years playing with stoves and boilers he has a long way to go
to catch up with Scrapper's 30 years plus experience on efm and other's coal burning units