ATTN: ALL BTR Builders (Gravely Model L)

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wayne z

wayne z

Active Member
Dec 5, 2010
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louisiana
OK, I'm curious as to how the oil gets back to the tank. Are you sure splash lubrication is part of this design? I thought splash system had oil stored in the crankcase below the crank with a dipper on the rod.
What splash this engine has is from the pumped oil leaving the bearings and being slung/blown all over in there before being coughed out of the 2 holes.

By the nature of a crankcase design like this with the enclosed flywheels, There is never much oil in it's crankcase. They use a scavenger pump, of larger displacement than the main pump, to insure that oil does not pool in the crankcase. the flywheels and rod can not run submersed in oil.

I have an '82 Harley that if I let it set a couple months, some oil leaks into the crankcase from the oil tank. When I first start it after sitting, It spits out about a cup of oil thru a special valve that's installed for that purpose.
Harley's also use a timed,rotary valve in the crankcase that lets crankcase air out on the piston downstrokes and closes on the upstrokes. This is to keep a slight vacuum in the crankcase so they don't leak any more than they already do.
The total air volume in this Gravely crankcase is very small compared to a normal, external flywheeled engine, and the piston displaces a LOT of air volume in the crankcase with each stroke. There's no way you could keep an oil level in the crankcase with the engine running. If you did , the oil would be churning and frothing from so much windage that the motor performance would suffer.
Maybe we could have a large hose like 1.5" hooked from one of the lower crankcase holes to the top of the oil tank, and use a large Gravely type breather cap on top the tank, letting the crankcase breathe thru the top portion of the tank, allowing the oil from the breather to pool in the tank.
 
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RicksRides

RicksRides

Member
Feb 22, 2012
864
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osceola IN
Wayne, I was asked a simple enough question yesterday that led to a interesting conversation. Was asked what kind of gear reduction or gearing I was going to use. His purpose in the question was a gear case on the bushing side of the motor Instead of adapting the engine, remove the gear from the shaft replace it with a #50 chain gear or bigger (have it supported by a bearing in the gear case itself) run a chain to a rear sprocket. Although gear reduction is not the problem. As he said it would give the oil some where to go and could be pumped to an oil tank where it would return it back to the crank case as quickly as its pumped out. It would lube the chain coming out of those holes and gather in the bottom of the gear box then pump oil to a tank. should cure a number of issues, oil frothing up, crankcase ventilation, mount the mag on it,etc..It would also give it more of a cycle look. Sounds plausable What are your thoughts about this
 
RicksRides

RicksRides

Member
Feb 22, 2012
864
6
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osceola IN
wayne z said:
OK, I'm curious as to how the oil gets back to the tank. Are you sure splash lubrication is part of this design? I thought splash system had oil stored in the crankcase below the crank with a dipper on the rod.
What splash this engine has is from the pumped oil leaving the bearings and being slung/blown all over in there before being coughed out of the 2 holes.

By the nature of a crankcase design like this with the enclosed flywheels, There is never much oil in it's crankcase. They use a scavenger pump, of larger displacement than the main pump, to insure that oil does not pool in the crankcase. the flywheels and rod can not run submersed in oil.

I have an '82 Harley that if I let it set a couple months, some oil leaks into the crankcase from the oil tank. When I first start it after sitting, It spits out about a cup of oil thru a special valve that's installed for that purpose.
Harley's also use a timed,rotary valve in the crankcase that lets crankcase air out on the piston downstrokes and closes on the upstrokes. This is to keep a slight vacuum in the crankcase so they don't leak any more than they already do.
The total air volume in this Gravely crankcase is very small compared to a normal, external flywheeled engine, and the piston displaces a LOT of air volume in the crankcase with each stroke. There's no way you could keep an oil level in the crankcase with the engine running. If you did , the oil would be churning and frothing from so much windage that the motor performance would suffer.
Maybe we could have a large hose like 1.5" hooked from one of the lower crankcase holes to the top of the oil tank, and use a large Gravely type breather cap on top the tank, letting the crankcase breathe thru the top portion of the tank, allowing the oil from the breather to pool in the tank.
Click to expand...
splashing thru the oil is what lubes the bottom end
 
wayne z

wayne z

Active Member
Dec 5, 2010
1,743
5
38
louisiana
RicksRides said:
splashing thru the oil is what lubes the bottom end
Click to expand...
No, I studied the oil system of the Gravely from some old literature.

The oil pump draws oil from the sump in the transmisson, and is pumped into that fitting high on the block on the tranny side, near the carb..
There is a port in the case from there that feeds the oil under pressure to the crankshaft stub. The stub is drilled to match a hole drilled in the flywheel half that connects to the crankpin.
The oil emitted from the lower rod bearing is slung and splashed around to lube the cylinder, wrist pin and cams and gears. The engine crankcase breathing thru the holes blows the excess oil into the transmisson case, where it pools in the sump.

That's a good idea about the gearcase for catching and breathing, but how do you plan to get the oil from there up to your oil tank?
Prolly be better to make a sump on the bottom of the gearcase to collect oil there for the pump to pick up.

After watching a utube video about how the Gravely gears work, I decided I am going to look into trying to use the stock gravely clutch and low/high planetary gears in a custom gearcase. Now That would be awesome!
 
RicksRides

RicksRides

Member
Feb 22, 2012
864
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osceola IN
Wayne do you have any links showing the path the oil takes thru the engine and tractor. I cant open any of my pdf's something corrupted. thanks
 
RicksRides

RicksRides

Member
Feb 22, 2012
864
6
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osceola IN
wayne z said:
That's a good idea about the gearcase for catching and breathing, but how do you plan to get the oil from there up to your oil tank?
Prolly be better to make a sump on the bottom of the gearcase to collect oil there for the pump to pick up.
Click to expand...
the gear cases real purpose was to act as a sump,Ill put a pumpinline to pump the oil thru the filter and into the oil tank where it can flow back to the engine. If I can open my files ill post a diagram to show my thoughts
 
truckd

truckd

Well-Known Member
Oct 19, 2010
2,837
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palmdale calif
I'd like to know how much for the rough ol bike that was posted on 4-9-12 and what size is the rim&tire? you can PM. about the inquire
Thanks!
 
wayne z

wayne z

Active Member
Dec 5, 2010
1,743
5
38
louisiana
RicksRides said:
the gear cases real purpose was to act as a sump,Ill put a pumpinline to pump the oil thru the filter and into the oil tank where it can flow back to the engine. If I can open my files ill post a diagram to show my thoughts
Click to expand...
Are you going to use 2 pumps? There needs to be pressurised oil fed to the crankshaft to lube the lower rod bearing and the whole bottom end from the oil slinging from there. I would think with the oil sump in the gearbox, the oil would be pumped thru the filter then to the crankshaft, just like the original system. Don't need an oil tank.
 
truckd

truckd

Well-Known Member
Oct 19, 2010
2,837
134
63
palmdale calif
Yes! that one, I have an old Schwiin Varsity("71") with all the bells and whistles that would make a great donor for parts, what size are the wheels 28" or 26"
 
RicksRides

RicksRides

Member
Feb 22, 2012
864
6
18
osceola IN
Picked up 3 rims this weekend a 21 inch front and rear rims off a pantera dirt bike and another 21in front off a kawasaki dirt bike. This is what im going to do. The front pantera rim will have the hub/brake assembly from the kawasaki rim laced into it. Then I'll lace the rear hub/brake assembly into the front kawasaki rim. They are both 21in with the kawasaki rim being a little wider. With tires on them they will be a bit over 26 inches tall. Because of the extra weight and power from using duel gravely engines I thought i'd use stronger wheels, better brakes, and a good set of tires. I beleive this bike will run out to 80mph or so, if it can I likely will and I'd really like to live thru it. The real 1913 HD claimed a 63.81 mph speed record
 

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RicksRides

RicksRides

Member
Feb 22, 2012
864
6
18
osceola IN
wayne z said:
Are you going to use 2 pumps? There needs to be pressurised oil fed to the crankshaft to lube the lower rod bearing and the whole bottom end from the oil slinging from there. I would think with the oil sump in the gearbox, the oil would be pumped thru the filter then to the crankshaft, just like the original system. Don't need an oil tank.
Click to expand...
Wayne , I beleive I will only need to use the original pump that on the engine.
 
HDCowboy

HDCowboy

Member
Jan 3, 2015
44
0
6
Texas Gulf Coast
Interested in seeing how this build turns out (or turned out), there is an old 70 something Gravely walk behind mower at my Moms place with what I think might be a Model L engine in it. I havent cranked that thing up in a couple years, last time the battery was dead but it was allways a strong runner. Would one that looks like this have whats considered an L engine in it?
 

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Ludwig II

Ludwig II

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Jul 17, 2012
5,071
783
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UK
I don't know anything of value about garden equipment, but I think it's probably got BS or To Come See (What's Wrong Now) at that age.
 
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