Open thread on Edwards 5 Radial

[tornitore45]

When I assembled the idler in the crankcase, I noticed the squirt oil hole falls exactly on the pitch line of the gear like someone intentionally wanted to create intermittent oil squirts.
I am taking a head clearing break before cutting the cam lobes on a part that has two days of machining on a tough 4330 steel that started already way oversized.

 

[petertha]

Can you show a pic? What is the hole connected to that it would squirt? On my radial I was thinking of pre-drilling a hole laterally through tooth so that when the cluster was clocked & tacked im place with Loctite, use the hole as guide & drill into the adjacent larger idler in order to permanently pin them together. Think the Edwards could be something like that?

 

[tornitore45]

I am not well equipped for pictures but will try to explain in words.

The hole I am referring to is in the crankcase. Is i tiny hole, the ends of an oil passage drilled in 3 segments into the crankcase. Looking at the drawing is obvious that the oil under the intermittent pressure of the plunger pump will will go straight out into the cam housing.
When all the parts involved are assembled, one notice something it was not immediately apparent from the drawings.
The hole in question happens to be on the pitch circumference of the idler 18 tooth gear. Every turn the oil pump squirts out a jet of oil. The oil squirt must negotiate through 18 tooth alternately obscuring and clearing the hole. The oil stream is chopped and scattered in the process.

 

[tornitore45]

Observation: The reason for all the spacers on the crankshaft is to guarantee that no axial forces are placed on the bearings when the prop nut is tightened.
All the inner races and spacers must pack together without any of the outer races bottoming into their seats.
Mind your tolerances because there is very little to guarantee the condition.
According to the plan dimensions there is only 0.001 left behind the front bearing seat when the bearing buts against the
Spacer 13-4 can be made a trifle longer if tolerance stack up are in the wrong direction.

 

[petertha]

You mean this oil passage maybe?

 

[tornitore45]

Exactly, that oil passage.

 

[petertha]

The location looks like its aiming oil at the idler gear cluster & like you say getting sprayed out & conveyed to ring gear. Not sure about the inclined 30-deg angle without a clearer view of the assembled components. I wonder how much of a squirt it puts out.

 

[tornitore45]

Hard to say. For every plunger stroke a certain about of oil is pumped out.
At least theoretically the volume can be calculated but that volume is split between two directions terminating with a 0.041 hole. The flow resistance of the two pats is very different, the majority of the of the oil will go to the crank cavity and the rest to the idler and cam cavity. Will play around when all parts are built. We can set it up all open and manually operate the plunger.

 

[tornitore45]

How do you cut your cams?
1)Rotary Table vertical using the face of a square-end End Mill? (Wrong)
2)Rotary Table vertical using a Slitting Saw no thicker than 0.025"? (Correct)

Case 1) You got your Angle/Lift Table One data point every degree
You start from the full Lift radius
Next rotate one degree lower the tool X thousands and cut
Did you also cut away the full lift spot?
Was the mill diameter small enough compared with the cut depth as not foul the already cut spot?

That is exactly what I did on top of not paying attention to the fact that the part was mounted in such a way to require CCWR but my rotary table degrees marking rise in CW rotation.

Case 2 The cam blank arc cut by the tool should be exactly 1 degree. More than that and there is the risk of cutting metal in the next 1 degree step.

One degree at radius 1.4" subtends an arc 0.024"

If you have to scrap a part with many hour on it is consoling to foul it up for two reasons instead of one.

 

[tornitore45]

There is another way to cut the cam properly.
Use an End Mill smaller than 1/4" not to cut past the middle groove into the other cam
Offset the spindle axis from the Rotary Table axis = Toll radius in such a way that the entire tool is over the un-machined part when you are on the descending flank and the offset sets the tool over the previously cut portion when machining the rising flank.
In other words keep the forward lip of the tool on the cam axis and the entire tool behind when climbing up, keep the rear edge of the tool on axis and the entire tool forward when stepping down.

 

[josodl1953]

You can look up in my thread of the Edwards how I milled the cam. I took an end mill and ground a recess in the mill deep enough to free the already milled cam. Easy-peasy....

Jos

 

[tornitore45]

Hi Jos, I see what you have done. The recess is to reach the far cam "walking" over the near one.
After considerable mulling over, head scratching and sketching I am now convinced that your method works, at no point is undercutting the cam.
A Woodruff seat cutter or a T-slot cutter will work too.

 

[mu38&Bg#]

Mauro, The cam profiles are symmetric. Is there actually a problem cutting "backwards"? As long as the overlap is somewhat close to designed, it will run. Oh, you must have ended up with the exhaust cam toward the front? What about switching the pushrods, or did you move the followers off center?

 

[tornitore45]

The tables are based on rotating the cam CCW while looking at the cavity (opposite the eccentric hub).
Depending on which end is mounted on the rotary table one has to match the rotary table degrees marks or run backward and match the table angle to a complement to 360.
A 3rd grader can understand that, if paying attention.

I slapped the part and started cranking.

The result is a mirror image of the cam where intake would be soon after exhaust.
Swapping the push rods would negate the mirroring except for the fact that the intake has a slightly different (practically meaningless) profile.

There is an even bigger blunder, and that is why I decided to remake it.
I have worked pretty hard to understand whether a square end End Mill would undercut the lobe, in other words chew up some of the machined part left behind going down and cutting metal ahead, that should not have, going up the slope.

With small steps, like 1 degree, a flat bottom tool will cut into the work if kept on axis, IF the local slope is 0.0039/degrees like the cam in question.
A round tool like a side cutting End Mill or a Ball Nose Mill will cut into the work IF the radius is large enough to encroach into the local slope.
My conclusion was that a tool over 6mm diameter will make "scallops" into the next 1.5 degrees step.

I have remapped the original data table saving each multiple of 3 degrees steps and interpolating the 1.5 degrees averaging the adjacent lift data. And will use a 6mm Ball Nose Mill.

Attached a PDF conversion of the spreadsheet to study the undercutting issue. unfortunately the cells formulas are missing but the formula used are spelled as text. We Know R1 Rt and Theta; R2 is the next radius to cut and is calculated, as the diagram shows, to be at the limit where undercutting starts. If R1-R2 (delta lift from the table) is ever more that the max allowed the tool is cutting where is not supposed to.

 

[tornitore45]

I am back, after forced vacations from mid April to end of August.
Spent time in Buffalo with family in-laws. Bored out of my skull away from my shop.
Anyway I completed the cam that had previously buggered up by making it mirror imaged and using a flat end mill the overcut the lobes.

As soon as I finished machining the eccentric it dawn on me that is not a good idea to have that mass twirling around at 1/4 RPM
I wish I though sooner and made it symmetric doubling the pump strokes.

 

[petertha]

Hi Mauro. I don't quite get your comment about the 'eccentric' (I assume you mean the crankshaft counterweight?). It has to (as much as possible) counter balance the large master rod & some portion of the extended link rods & pistons in their semi-rotating, semi-reciprocating motion. Actually compared to some other radials, the Edwards counterweight slug almost looks smallish by comparison, but the devil is in the mass/volume/distance/design details. What do you mean by symmetric doubling the pump strokes.

 

[tornitore45]

I am not talking about the crank.
The cam ring has an eccentric driving the sump pump plunger.
One stroke each turn. The eccentric is inherently unbalanced. By placing two lobes 180* apart the eccentric is transformed into a 2 lobes cam, giving two strokes for each revolution and eliminating the unbalance. I do not know if the pump plunger can "follow" at double the cam RPM which is 1/4 of the crankshaft RPM.

 

[josodl1953]

Dozens of Edwards already built run well with this eccentric. Recommended RPM of the Edwards is 6000, so the eccentric runs at only 1500 RPM, not dramatic. You must bear in mind that the plunger needs time to return to the end of the suction stroke, especially with a viscous oil as castor oil. I would leave as it is.

Jos

 

[tornitore45]

Good point, Jos.

 

[tornitore45]

I am starting to machine the heads and have a conundrum.
My plan is to use bronze valve guides inserts.
The head is conical surface, therefore the resulting valve seat is the intersection of two cones resulting in a strip of variable thickness.
Standard practice mandates that the best valve seal is obtained with a very thin seat. Cutting the seat into the conical head will not be optimal because to guarantee a minimal seat, there will be wider areas where leaks are more likely to manifest.
I have two options:
1) Insert the sleeve before machining the conical portion and then machine the assembly. The valve sleeve end will be part of a conical surface. Seat problem mentioned above.
2) Machine the head conical combustion chamber surface before inserting the sleeve, then cut the valve seat on the planar end of the sleeve. Nice thin seat, but difficulty in controlling the alignment of the sleeve into the conical combustion chamber.

I like to hear how any of you have attacked this issue.