Open thread on Edwards 5 Radial

[stevehuckss396]

Can the head be machined so a valve cage be installed. That way the only decision to make would be the depth of the cage to get the face of the valve where you want it. Any angle inside the combustion chamber becomes irrelevant because the valve is reliant on the cage only. Make the head of the valve about 0.010 inches smaller than the diameter of the cage. Press them in and then cut a seat with a Gbritnell style cutter and your all set.

 

[josodl1953]

I agree with Steve, see post # 17 and the following on my thread of the Edwards.I did all the machining of the valve cage(valve seats included) before pressing in. In this way , you are sure that valve seat and guide are perfectly aligned. I used aluminium bronze for the cages, others prefer phosporous bronze. I would't use normal bronze as it is not particularly hi-temp resistant.

Jos

 

[petertha]

This is an older sketch of how I am doing mine. Its a hemispherical combustion chamber shape vs. your conical, but similar issue. I plan to use integral valve guide/seat cages. The thought was slip fit & made permanent with HT Loctite to minimize distortion. Then the final seat cut on the crown edge in-situ, vacuum test the valve fit etc. The cage needs to be installed permanently before the gas passage is drilled through the head & into the cage.

In this sketch was playing around with different combinations of cage lip depth, seat profile & valve dimensions. The actual valve is a bit thinner section beyond the 45-deg fave which helps it fit a bit better. End result looks similar has one valve edge slightly proud & the other slightly recessed. There is a slight change to CR depending on how you do this but mostly I was concerned about a gap that might trap junk, so its more like blended chamfers. All this is a function of your particular head geometry so best to draw it out. These are just being machined so you will have to wait to see how/if it works. Everything looks OK on the workbench, real life may be different.

 

[tornitore45]

I definitively give up the idea to insert the cages before machining the conic combustion chamber, making the cages completely embedded, and indistinguishable from the head geometry per plan, except the metal color difference will show it off.

I am going the approach all of you describe.
The cage/guide will enter the combustion chamber as a flat top cylinder.
I am not set on the level of protrusion/set-back. I am making some test valve- sleeves in aluminum that easy slide in to see what dept looks better, before I commit to press fit. I have no feeling on the mismatch between the conic chamber and the cylindrical sleeve show at the intersection. May be a serious consideration on altering the compression ratio or may be nearly invisible.

Thank you guys.

 

[petertha]

I don't want to impose non-Edwards pics on your thread but I'm finally returning to the shop after summer activities & completion of my somewhat similar radial heads will be the next task. Here you can see some mockup pics of cages & valves in the hemi heads. Right now I am at kind of at a decision impasse on the valve seat method. On one style of cage I have pre-chamfered 2 angles at 30 & 60 deg. The cage would get inserted & then the 45-deg valve seat made on the crown with the seating tool ~ .010" wide. The other style of cage just has a sharp 90-deg edge, basically like a tube. It must reside a bit further into the head. The 45-deg seat is then cut on that edge. There are pros & cons to both but the second is net easier to make & possibly a bit more robust. In both cases the valve is about as flush looking as I can make it. I'm going to have to make a decision here pretty soon.

 

[tornitore45]

Peter, you are welcome to post any picture that clarify the topic. I have decided to back off the valve cage just enough to bury as mach of the valve head into the conic head to have the smoothest combustion chamber shape. In other words there will be some deviation from a perfect cone, some voids and some stick out. I can not fully visualize the situation but know what will have to do.
Since I use valve cages, I will cut my seat when the cage is chucked up for the boring, that way the seat is concentric. Seat at 45 degree and valve at 47 degrees.
Valve and seat will meet with zero area in common ( because of the angle difference).
Grinding the valve with carbide grit will show a dull gray area on the valve an a dull bronze area on the seat. When the width of the dull area goes all the way around and is the right width I know I am done.

I usually silver braze a SS head on a drill rod stem because I can not trust my lathe to make the stem parallel. I finish machining the head after brazing, of course.
Is a bit tricky, but after so many valves made I got the technique down.

 

[petertha]

Just eyeballing the section view & how my cages were configured, it might look something like this. The devil is in the details. There are a few critical clearances that crop up here & there which are hard to visualize without being able to slice sections at specific orientations.

 

[tornitore45]

I know exactly what you mean. There is just enough metal to place a valve cage but not much to spare around the inlet/outlet ducts.
I had to redraw the cross section and calculate all the dimensions with particular attention to the tiny metal left between hollow spaces.
Also while the drawings dimensioning fully defines the part, the dimension given are totally useless when you go to machine the part. Seemed like I was back in High School resolving all those little triangles to get all the useful dimension to machine the part.
I am almost done, I mounted the head to a fixture plate by the 5 screws.
The plate is mounted to the inclined table set at 20*.
After making one head, I am machining the other four in "parallel" one feature at the time on all four, because I feel it avoid mistakes. I am working on a manual machine with NO DRO. Going slowly.
Thanks for your assistance.

 

[bobden72]

I have built the Edwards Five as per the drawings and it runs fine, but this thread on valve cages is all good stuff and very enlightening, think I can see now where I went wrong with me Cirrus. I will have to get it down from the shelf and redo the valves. Thanks chaps.

 

[tornitore45]

I am at a point where I need to buy the glow plugs
Any suggestion on what Heat Range works best for this engine?
The drawing call for "Fox Long with Idle Bar" But I could not locate such.

 

[Glorfindel]

I am at a point where I need to buy the glow plugs
Any suggestion on what Heat Range works best for this engine?
The drawing call for "Fox Long with Idle Bar" But I could not locate such.

Os #F glow plug.

Someone got a dawing of a good glow plug driver???

 

[tornitore45]

GLOW PLUG DRIVER
I have a tentative idea to use a Switch Mode Regulator to feed all 5 plugs from a 12V battery. It may be also a way to change the "heat" of the plug by trimming the voltage, may be, do not know. I will cross that bridge when I come to.

One consideration is that the plug tip is probably buried below the 0.5" cavity and difficult a access with the usual "radial entry" clips.
I am trying to come up with a reliable snap on contact and permanently wire all 5 to common point.

 

[Glorfindel]

GLOW PLUG DRIVER
I have a tentative idea to use a Switch Mode Regulator to feed all 5 plugs from a 12V battery. It may be also a way to change the "heat" of the plug by trimming the voltage, may be, do not know. I will cross that bridge when I come to.

One consideration is that the plug tip is probably buried below the 0.5" cavity and difficult a access with the usual "radial entry" clips.
I am trying to come up with a reliable snap on contact and permanently wire all 5 to common point.

I did rc airplane modeling for about 15 years. I have a panel, driven by a 12v battery and it's adjustable, but i dobt think he can drive 5 plugs at time. I'll dismantle it and see what i can do.

Maybe i'll come up with a simple circuit bord drawing.

 

[stevehuckss396]

I have some 4 channel drivers I built years ago. They are 12Vdc in and 1.2Vdc output. They work great on the Cox glow plugs. Don't know if they would work for you but your welcome to them for the price of shipping

 

[josodl1953]

This is my setup for the valve cage, somewhat similar of Peter's setup. Only I mover teh inlet and exhaust ports(dimension A)
a bit upwards to create more sealing surface on point B, especially for the exhaust. The exhaust valve seat must get rid of the heat so heat transfer from the cage to the head is important.

If you have doubts about cavities, ports etc interfering with each other I find it useful to make a dummy of wood, plastic or any inexpensive material.

Glow plug leads are ready available in most R/C shops. Only I had to mill some extra material to free the rectangular plug cap.

 

[tornitore45]

[URL='https://www.homemodelenginemachinist.com/members/josodl1953.24431/']josodl1953 Your picture looks exactly like my plan. Good idea to lift the ducts hole since there is more margin atop than near the valve seat where we want some beef.[/URL]
Did not think to make room for the plug exit. The wire wants to go in that direction anyway and is weight off (not much). I did not like the idea of a wire going out on axis and loop back anyway.
I am done with what I consider the difficult machining of the heads, what is left is cages and fins. I have to make the valves first to see how they nest in the heads. I will probably copy your top fins size, the drawing call for something too fragile.

 

[petertha]

Looks good. Some things to ponder as you advance through your prototype.

- consider how you will reliably make a flat bottom hole and of the correct ID simultaneously. You can't effectively ream the hole because the reamer has a chamfer. An end mill doesn't typically have a sharp corner and a perfectly flat bottom but that's what I found to be best compromise, unless you have one of those nice traversing boring heads. Its better to err on a couple thou deeper to land the cage slightly off bottom if necessary according to how the valve positions. A gap isn't great but maybe would be Loctite filled anyways, not much different than bonding the annular wall.

- you will need some reliable datum to pre-register the cutting tool because it will be entering your cone chamber at a funky angle. In my case it was better to use the jig datum, but your mileage may vary.

- I found it better to select the cutting tool (10mm EM in my case) & then work out the valve cage OD from that for the appropriate fit. I chamfered the crown of the valve cage so it has clearance relative to counterbore corner.

- In my case it was better to drill the pilot hole first (corresponding to the valves stem). This removes material at the center where the EM doesn't like to plunge very well. You can decide if you want that segment to be glued as well as the cage for extra retention or make it a clearance hole. I had difficulty with the former. Only issue is its a longer pilot hole with smaller diameter so higher propensity to drift.

- Terry cut radial grooves in his valve cage OD's to take up excess Loctite. I haven tried that yet. But I did get a surprise on one tester that set up a lot quicker than I expected. They were squeaky clean & just a bit closer gap on that particular set. No primer or kicker or anything. Not sure what was going on there but do some tests before your real head.

What is the valve seat contact length you are designing for? That's another thing I am messing with. I want it to be about 0.010" via the valve seat cutter & leave me 0.005" truing/lapping allowance. Seems like when folks make it wider, say 20-30 thou, more difficulty sealing. Another consideration is where that valve seat facet on the cage contacts the 45-deg valve face. If the contact point is out near the valve OD that keeps the valve higher up into the cage & a more flush appearance in the combustion chamber when valve closed. If the contact point is more inboard towards the valve stem, the opposite occurs - valve kind of sticks proud. I finally realized this on another radial design where the valves stuck out (easier to make the cages) but had requisite scallops in the piston top to compensate. So yes, best to make the valve now so you can check the interaction of the combined assembly.

 

[petertha]

I have some 4 channel drivers I built years ago. They are 12Vdc in and 1.2Vdc output. They work great on the Cox glow plugs. Don't know if they would work for you but your welcome to them for the price of shipping

Its been a long time since I've seen a Cox (but I still have finger scars Haha). I seem to recall 1.2 volts, or maybe it was 1.5v nominal cell voltage with the typical long wire lead (resistance) that resulted in that at the clip. Regular glow plugs can take a bit more, like 1.5-2.0V. But the trick is current. I seem to recall ~3A.

Did you design that circuit yourself? Its something I'm going to have to tackle one day soon.

 

[stevehuckss396]

I'm not sure how it came about. I remember Jerry James programming the pic so it may have been a circuit he designed. I tried it and it worked well. Used it on the hwx 4. If a modern glow plug needs 1.5-2.0 volts this may not work.

 

[tornitore45]

Peter, I have addressed all your points the same way you describe.
I pre-drilled an reamed for 1/4" dowel to be used to re center the hole on the other side. Used a new 1/2" carbide end mill that did a good job, the corner is visually sharp but the valve cage is chamfered to seat on the bottom.

I made a sliding fit test cage to get the length verified then will duplicate on the real parts.

I am not fond of Loctite in a hot application. I have developed sufficient accuracy to be able to make a shrink fit reliably. Use a heat gun on the aluminum and the part is kept in ice water then it drops in without fuss. Stopped using a torch long ago when I melted the aluminum part.
Agree on the thin valve seat.

I used a fixture registering the head with the five screws, the little slop left was corrected by moving the table until the dowel in the quill reentered the hole freely.
Turned out well.

Plug Driver
5 plug at 3A need a 1.5V(adjustable) 15A regulator from a 12V source.
I was a power supply designer for 40 years and this is no different than a typical PC supply. The only issue is that I do not like home grown electronic project, I do not have all the parts and equipment I am accustomed to have working professionally.