Forrest Edwards radial 5

[Mechanicboy]

Use Loctite 5770 High Temperature Thread Sealant instead epoxy + press fit. I prefer valve cage of bronce + valve of stainless steel , last very well.

Loctite 5770 High Temperature Thread Sealant works as a lubricant to mount valve cage into cylinder head and keep gas tight when locktite is hardened.

 

[josodl1953]

Thanks Jens, I keep it in mind. I wonder what type of bronze you are referring to. Usual bronze contains tin which, because of is low melting point, makes the bronze less resistant to heat.
Nice place Bergen, by the wat. Been there once..

 

[Mechanicboy]

Alloy material is the melting temperature of the tin no problem as it is mixed into copper that has a high melting temperature and then bronze has a slightly lower melting temperature than pure copper. Valve cage receives cooling via the cylinder head.

I used common bronze who are available in Norway either it's bronze or aluminiumbronze. Abration no problem.

Nice to hear from you about Bergen

 

[josodl1953]

For the pressing operation I made a pair of tools to properly support the cage and cylinderhead.

I had once, a long time ago, salvaged an old press from the scrapheap of a metal testing laboratory. It cam on handy for this opeation, with the help of a hydraulic car jack.

All went rather well, some cages needed mor force to install than others but in the end all were in place. Looks rather nice..

So far so good. Next: drilling of intake and exhaust ports.

 

[josodl1953]

Because I wanted as mich space between the ports and the valve seat I calculated that 7 mm would be a good value. To test this I took a pair of wooden cylinder heads I made for the mockup at the start of this project. I made aluminium valve guides, pressed them in ad drilled the ports which turned out to be rather well. The drill slightly touched the valve guides but I do not thik this is a big problem so I carried on with the "real "heads.

Next step was drilling and tapping of the inlet and exhaust flange mounting holes. I did this with yet another drilling jig.

So,with the most important operations on the cylinder heads complete, I only had to cut the side cooling fins. Normally this would be done with a sawmill but iI preferred to do i by turnig with a parting tool. To fit the head in the chuck I made a fixture on which I could mount the head in four different positions. A bit elaborate , but it does the job ant the result war satisfactory.

 

[josodl1953]

Meet Butch, he is my purrrrring prroject superrvisorrr.

He keeps me company while I am busy in my workshop.....

I have been considering the design of the valve retainer and decided that it was beyond my abilities to make such a tiny cone and the spli in two equal halves... Instead, I adopten the retainer design that Terry Mayhugh used for his quarter scale Merlin . Only I made the C- retainer from 1 mm sheet steel instead of turning and milling it from bar stock and parting them off. I found a piece of 4130 steel - heaven knows where is came from..- which seemd a pretty good quality.
I drilled the holes first, them cut them loose. The square pieces where then turned on a mandrel. The slots where made using a grinding disc on the Dremel.

The valve springs were a bit of a headache. At first I looked for commercial springs but I could not find the correct size.
Making them myself was a problem because getting the correct pitch by hand was almost impossible. Material was no problem because I had a coil of spirng wire of the correct thickness hanging around ( literally!) in my workshop for many years. Th bsolution was electric copper installation wire. I nhad the correct thickness to fit in between the coils of the spring wire. So I made a mandrel and a retainer for both the copper and the spring wire. Setting the lathe at it lowest speed and using the handle operated belt tensioner of the lathe as a clutch I was able to make the springs.

 

[petertha]

Radial I'm building has this sort of spring keeper arrangement. Uses a commercial groove retainer and a machined part. Maybe will provide some ideas.

 

[josodl1953]

Looks nice Peter. Do ypu have a thread of this build?

 

[petertha]

Thanks. Yes I'm going to start a build thread hopefully soon. I'll backtrack with the pictures I have saved & carry on with making the 5 cylinder assemblies which I will be commencing his winter. I had a busy non-machining summer & just acquired a new milling machine recently so shop is still in upheaval as I get it set up & re-settled in for winter metalworking again.

I was just looking at the Edwards head for other reasons the other day for a different reason. Now I see the tapered cones being referenced. Maybe other Edwards builders have some better direct insight to that aspect of design & can comment. The Ohrdorf parts aren't difficult to make but it does tie into dimensional issues of the spring itself (Length, max/min OD & ID)... so collectively spring force & action movement. IE. there may be some latitude to modify the design, but there may also be constraints depending what parts are already machined.

 

[bazmak]

Nothing wrong with using a lathe as a mill if your prepared to accept the inconvenience and additional time needed for setup and changing setup etc

 

[josodl1953]

Yes, that is VERY true. I spent a lot of time fabricating jigs, fixtures, gages etc.

Peter, I considered possible dimensional issues. Before fabricating an assembly, I always make prototypes from scrap material to check interaction of various parts. In case of the valve train, I found out that I needed longer valve stems which in turn lead to longer rocker brackets. But since I had to recalculate the whole engine design beacuse of the metric conversion and the downsizing this was only a minor issue .

This is how my cylinder head assembly looks like:

 

[petertha]

Coming along nice. Sheesh, you are converting imperial engine to metric units and I am converting metric engine to my inch for my machining equipment!

When you pressed your valve cages in, you mentioned some required a bit more force. Did you end up using an adhesive like Loctite or is it an interference fit? Were the 45-deg valve contact faces cut in after the cages were pressed in or existed beforehand or ? I'm curious about any distortion or sealing of the valve. But maybe that part of build is still coming.

 

[Chiptosser]

fantastic! You Sir, are very patient and persistent.
It is great to see what can be done, With the equipment that you have a available (unavailable) to undertake a project like this .
Great Work!

 

[JohnBDownunder]

Great build thread that I have just read from Pg1 to here. Informative and to the point by a jig maker extraordinaire showing patience and ingenuity. Thank you for posting and I trust we get to see a finished, running engine when you are satisfied with the result.
Congrats,
John B

 

[josodl1953]

Thank you for your comments.
Peter, I used interference fits ( 0,01-0,02 mm) . Using Loctite would be an easier option but I was worried about the heat transfer between the valve seats and the cylinder head if there would be a thin layer of Loctite between them. This would probably not a problem for short demo runs but I intend to use this engine on a R/C plane. Internal dimensions ( valve guide, transfer and valve seat) were machined in one operation to ensure perfect alignment. I don't know yet if the valve seats are distorted during pressing in because I have not lapped the valves yet so wish me luck.....

Jos

 

[Raviv]

great work!
i am trying to take a similar root designing my own radial engine.
it is recommended that you take a cross cut to the wooden mock-up that you did in order to understand how close the ports actually are.
since i am designing my engine in CAD, and printing it using my 3D printer, its easier to have an understanding on how the parts actually integrates with each other.
learnt a lot from your post so far, thanks.

 

[josodl1953]

I made a plastic model as you can see in a previous post, this is also helpful.

 

[josodl1953]

Proceeding with the rocker brackets, I had to make a drill jig for the bolthole because there is very little room for error. The hole dia is 2,5 mm, the thickness is 5 mm so there is only 1,25 mm material left on both sides of the hole. The jig consists of 5 parts, two spacers, one block with the drilling hole, and two sideplates held together with six 2 mm Allen bolts and nuts.

Milling the slot and drilling and reaming of the pivot shaft called for some fixtures .. as usual ..

For grinding the C-clip grooves in the rocker pivot pin I use my home made toolpost grinder.

 

[josodl1953]

Fabricating the rocker arms was a bit more complicated. Harvesting material from a slice of what appeared a sample of a thick-walled aluminium tube involved milling, drilling and good old elbow steam sawing. Only the sawblade didn't make it to the end ... tough stuff, that..

Drilling of the holes for pivot pin, rocker button and adjusting screw involved making a.... drill jig.

After drilling, it eas just a matter of removing excess material by several milling and turning operations, pics are self-explanatory.

 

[josodl1953]

With the valve train complete, I went on with the cylinder liners and barrels. I cut the cooling fins with the barrel fitted on a mandrel, using

a parting tool.

Turning the liners was pretty straightforward, so no pictures. I used a light shrink fit of about 0,02 mm so after fitting them in the barrels I had to rework some of the bores to avoid the piston from seizing up at TDC.

Looks rather nice....

Merry Christmas everyone!


Jos