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Gear Identification Help/Confirmation

JasonPAtkins

Hot Rolled
Joined
Sep 30, 2010
Location
Guinea-Bissau, West Africa
I'm a novice gear-er, having only dealt with calculating such things once in the past, in order to fix a lathe feed gear.

The short story is that I'm trying to introduce a roughly 10:1 reduction into a mortar mixer. I'm helping set up a factory over here to make drinking water filters to help with the many waterbourn diseases that give people chronic diarrhea. The mixer is spinning too fast for the clay/sawdust/water mixture we use to make the ceramic water filters. Rather than getting the mixture to ball up and roll over and over, it just smears the clay against the wall of the pan, packing it denser and denser with every revolution, until it eventually stalls. We may also need to change the mixer paddle geometry, but by watching videos of other factories around the world making these same kind of affordable ceramic water filters, we know they're successfully mixing closer to 6rpm rather than the 60rpm we're getting.

The current solution is not the best one available. I admit that, but ask for your help anyway. An enclosed worm gear reduction unit would be much more appropriate, much tougher, and last a lot longer. I don't have a way to get one of those right away. Perhaps if this solution works for a year or two, that will be the proof of concept and give us time to send the worm drive over.

The current mixer "gear train" is: Honda gas engine with some reduction built into it -> dual belt sheave pair -> pinion gear to big gear pair -> mixer paddle shaft.

Mixer diagrams for this model are here, in case that explanation isn't clear.

I'm proposing to add an intermediate shaft on pillow bearings that would change the arrangement to be this: Honda gas engine with some reduction built into it -> dual belt sheave pair -> small 14 tooth 12DP gear to 144 tooth 12dp gear ->pinion gear to big gear pair -> mixer paddle shaft.

If I order it today from Amazon, I can buy the 14 tooth gear and have visitors bring it with them next week. It's small. The big one, they won't have weight for. Fortunately, I found this little gem at the scrap yard a year ago and grabbed it, assuming a project like this might come along eventually.

IMG_20160624_111617 (Large).jpg

Machining the hub doesn't seem too tough, and I have a 1/4" push broach, so I'm planning on a turning a hub with 1" ID, 2.5" OD, plasma cutting a piece of plate with a 2.5" ID and 10.75" OD, and welding the three together.

So, I have one chance to order the matching 14T gear!

The scrap-yard gear ring is 144T. It mics at 12.080" for an OD. Using DP=(T+2)/OD gives DP=146/12.080=12.086DP. Obviously, that's not right. So, I'm left with two choices: 1) The gear teeth are a bit worn, or 2) it's a metric module gear.

In support of idea #1:
To make it a clean 12DP, the OD would have to be OD=(T+2)/DP=146/12=12.166" OD. That would mean half the difference of wear, =(12.166-12.080)/2)=.043" of wear on each side. Given the following photo, I think I might be able to believe that.

IMG_20160624_112331 (Large).jpg

In support of #2:
The gear is exactly 12.00mm wide, so it's either an imperial/metric mutt, or the teeth are metric to match the face width.

However, the calculations there would be MOD=(T+2)/OD=146/306.832mm (measured)=0.475MOD. That's not standard. To make it a standard 0.5MOD gear, it would have to be OD=(T+2)/MOD=146t/0.5mod=292mm=11.496" or for 0.4MOD, OD=(T+2)/MOD=146/0.4MOD=365mm OD=14.37". Obviously, it's far from either of those.

Given that, it seems most logical to assume it's a slightly worn 12DP gear that happens to be a metric mutt, having a 12mm face width, does it not?

-----------------

Second issue is pressure angle. 14.5 degree is the stubbier, right, and 20 is the pointier? If so, I have to vote for this being 14.5, and even then a bit worn. Seem logical?

IMG_20160624_105126 (Large).jpg
 

johnoder

Diamond
Joined
Jul 16, 2004
Location
Houston, TX USA
Its already noisy with the IC engine, just give it some room and let it run. By room, I mean put the gears a little further apart. 0.010" extra would probably do
 

JasonPAtkins

Hot Rolled
Joined
Sep 30, 2010
Location
Guinea-Bissau, West Africa
Wouldn't chain and sprockets be a better, longer lasting and cheaper fix?

Hmmm... probably. A 120 tooth #40 sprocket is an 18" OD piece of steel plate though. I can't ask someone to bring that. My cnc plasma table is down, but the same people are bringing parts to hopefully fix it. If that fix is successful, I suppose I could plasma cut it (I have a program to generate sprocket cad designs), but I'd be worried that the slight plasma bevel plus nitrided edge will destroy chain faster than we can replace it. A form cutter to clean up the bevel would be a PITA on the mill because of the workpiece OD. Maybe it would be good enough to put my students to work with a round file to clean up each tooth?
 

Clive603

Titanium
Joined
Aug 2, 2008
Location
Sussex, England
That gear looks to have started out with some sort of stub form teeth. Coupled with wear makes proper ID a bear. As you have found.

Lateral thinking time. As you propose to add an intermediate shaft for the extra gear reduction why not use the extra shaft to replace the original double Vee belt primary drive single stage speed reducer with a two stage poly-Vee belt system. Poly Vee pulleys are a lot easier to make than Vee type and power transmission for a given width is much higher. Couple of poly-Vee belts won't take up much weight or space in transport either. Might even be something findable local for automotive uses, bet the length is inconvenient tho'. Original is about 1.8 to 1 if I read the parts book right so two 4:1 stages ought to work without unreasonable pulley sizes.

Clive
 

HuFlungDung

Diamond
Joined
Jan 19, 2005
Location
Canada
Isn't that just a ring gear off a flywheel? Should be starters laying around in the junk where you could grab the gear off and adapt it.
 

72bwhite

Titanium
Joined
Sep 26, 2012
Location
California, Ventura county
Hmmm... probably. A 120 tooth #40 sprocket is an 18" OD piece of steel plate though. I can't ask someone to bring that. My cnc plasma table is down, but the same people are bringing parts to hopefully fix it. If that fix is successful, I suppose I could plasma cut it (I have a program to generate sprocket cad designs), but I'd be worried that the slight plasma bevel plus nitrided edge will destroy chain faster than we can replace it. A form cutter to clean up the bevel would be a PITA on the mill because of the workpiece OD. Maybe it would be good enough to put my students to work with a round file to clean up each tooth?

That's the wrong approach way out in the boonies you bring in a finished sprocket
at a fraction of the weight not a chunk of steel to make one.

belts and pulleys is the way to go you could use aluminum pulleys, and for maintenance
the locals would have an easy time sourcing replacements, go with flat leather and they
could fab a replacement belt.

get a grant form some do gooder organization.

set up to do aluminum casting.
is there relatively large quantities of scrap cast iron around,
that can be melted and cast to make parts in very primitive conditions.

you can get 180 pounds of freight by doing away with one passenger in a small plane.
 

72bwhite

Titanium
Joined
Sep 26, 2012
Location
California, Ventura county
I actually own a mixer like that,
you have to put your water in first then add the dry ingredients.
60 rpm seems on the fast side.
there is a little learning on the mixing feeding technique.
a 5hp low rmp electric motor works well for power
 








 
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