Open thread on Edwards 5 Radial

[tornitore45]

Hy guys, there are several threads on the Edwards 5 some quite old.
I opened this thread to discuss any issue without hijacking any other thread dedicated to a single topic.
If you have a question, a problem, a suggestion or anything related to the subject you are welcome on this thread.

I start with one:
I believe have the latest drawing of the Oil Pump
Sheet 26 Rev A02
Sheet 27 Rev A00
Sheet 28 Rev A01

I suppose that the RH side of the pump as drawn is the suction part and the LH side is the output side.
I cannot figure how the pumping action works relating to the operation of the check valves.
How can a 0.125 ball in a 0.125 hole act as check valve
On the suction side the ball runs into a 0,136 hole, but I fail to recognize the seating seal.
Are the brass tubes on the right between body and cover part of the ball seat, requiring to have a
smooth & square lip?
Has anybody run the pump and observe oil moving through?

 

[mu38&Bg#]

The prints say the bores the balls are in are Ø.136"

 

[tornitore45]

Thanks, on close inspection you are right. I was mislead by the view with assembled plugs that seem to match the hole. I can see the plug is 0.125 and the seal is entrusted to the O-ring.

 

[tornitore45]

Question about Cam/Crankshaft phasing
Fixing the cam lobe position, the crankshaft position depends on 4 variables
1) The pinion orientation on the crankshaft
2) The two gears on the idler shaft gears relative position
3) The ring gear position in the cam hub
4) The 18 to 18 gear engagement can move +/- 20 degrees, by slipping one tooth

The drawing do not specify the position of gear teeth in reference to the mounting on shafts, therefore in the worst case the ring gear can be 1/2 tooth off the correct position. 1/2 tooth is 3.75 cam degrees which translates to 15 crank degrees after the 4:1 ratio.

The combination of the +/- 15 degrees error on the ring and a possible +/- 20 degree correction at the crank/idler engagement result in a maximum error of +/- 10 degrees of crank. ( worst situation is when the ring is off only 10 degrees and no correction is the best option.)

10 degrees is not much but is probably enough to make a difference on the top performance.

Any comment or previous wisdom on this?

 

[Glorfindel]

Question about Cam/Crankshaft phasing
Fixing the cam lobe position, the crankshaft position depends on 4 variables
1) The pinion orientation on the crankshaft
2) The two gears on the idler shaft gears relative position
3) The ring gear position in the cam hub
4) The 18 to 18 gear engagement can move +/- 20 degrees, by slipping one tooth

The drawing do not specify the position of gear teeth in reference to the mounting on shafts, therefore in the worst case the ring gear can be 1/2 tooth off the correct position. 1/2 tooth is 3.75 cam degrees which translates to 15 crank degrees after the 4:1 ratio.

The combination of the +/- 15 degrees error on the ring and a possible +/- 20 degree correction at the crank/idler engagement result in a maximum error of +/- 10 degrees of crank. ( worst situation is when the ring is off only 10 degrees and no correction is the best option.)

10 degrees is not much but is probably enough to make a difference on the top performance.

Any comment or previous wisdom on this?

I will do slothed (oblong) holes in the cam for fine tuning.

 

[petertha]

I'm building a similar (Ohrndorf) 5-cyl radial so will be interested in replies. Mine is similar layout: crankshaft gear > idler-1 gear > idler-2 gear > cam plate ring gear.
Idler 1 and 2 are on a common shaft but they are mated when in final timed position.

The way I understand it is:
- hard attach (meaning Loktite or whatever) crankshaft gear to crankshaft
- hard attach ring gear to cam plate
- assemble gear train, all teeth are meshed but idler-2 is still free to rotate as cam gear is clocked into position
- now you are ready to time both crankshaft & cam plate for a known (important!) relationship point like intake valve open at X degrees BTDC on a specified cylinder. That sets the idler-1 & idler-2 position relative to one another. Now, how this relationship is preserved during disassembly so it they can be permanently fixed to one another for future assembly.... I'll be crossing that bridge myself. So would be good to know any tricks.

There may be other permutations of which gear is left floating vs. fixed, but this is how I understand the process.

 

[Glorfindel]

I will do slothed (oblong) holes in the cam for fine tuning.

Like this one. Plus i'll pre drill 3 holes on the gears to be able to put pins and block everything.

 

[tornitore45]

Good suggestion. I would make the fit of the idler gear on the common shaft a bit tight. Movable as one adjust the phasing but tight enough to stay put during disassembly. Then when the idler is free place a collet on each and hold in the late or the mill, lock the spindle from rotation and pull the gears apart. Place the Loctite and push together. The original relation should be preserved.

Which bring us to the next question: What is the specification for the phasing, does anyone know?

 

[tornitore45]

Glorfindel are those oval holes for the #2 screw threading into the ring gear?
Did you machined the eccentric as an integral part? I was thinking of doing just that.

 

[Glorfindel]

Glorfindel are those oval holes for the #2 screw threading into the ring gear?
Did you machined the eccentric as an integral part? I was thinking of doing just that.

It's not my parts, but i saw it in another forum and liked the idea.


Yes, those oval holes are for threading in the gear. Plus i will do 3 more holes in the ring gear (to put pins) to fix everything when it will be setted.

 

[tornitore45]

Another subject
The crankshaft has 4 ball bearing on it. If we do a good job at turning the seats and the shaft journals, the shaft is not going to come out without some serious pounding. Are you considering making a miniature extractor, like the typical gear puller, to push the shaft out. Also the prop hub will seize on the split cone and need pulling.
I envision placing 6 threaded holes in the prop hub for mounting the propeller and those can be used for the puller.
There is plenty of room on the cam housing nose to place blind threaded holes for the puller studs.

 

[tornitore45]

Returning to phasing the cam
There is sufficient room between the intake and exhaust cam tracks to place a 4-40 set screw to temporarily lock the cam to the ring gear before the holes are drilled in the gear. Once the phase is found the hole can be drilled in that position. The ring gear has now an inside and outside that should be identified by a mark.
A tapped hole could even be made in the cam housing to access the set screw if trial and error is not palatable.
The ovalized holes in the cam imply a trial and error method which requires disassembly. I am of the opinion that disassembly should be avoided. There will be already too many occasion to do it and pushing the bearing in and out on the shaft may loosen the tight fit recommended for bearing mounting.

 

[petertha]

Another subject
The crankshaft has 4 ball bearing on it. If we do a good job at turning the seats and the shaft journals, the shaft is not going to come out without some serious pounding. Are you considering making a miniature extractor, like the typical gear puller, to push the shaft out. Also the prop hub will seize on the split cone and need pulling.

I've completed these parts on a similar radial with comparable bearing layout. Some bearings are hard attached to other sub-components (as evidenced by the bearing stop flange on one side or another) and these sub-assemblies slide on the crankshaft in a sequential order. Whereas the big bearing is first attached to the crankshaft itself & so last to come off during complete disassembly. So there is no pounding involved & the shaft cant come out in a single push extraction. Some of the assembly nuances become more apparent when you stare at the drawings long enough or when the parts are made. Relative fits are very important & many of those are not really specified.

Often the face of the hub is tapped to facilitate puller studs, not a bad idea. The taper of the of the slit cone is supposed to help with this or usually just a bit of heat does the trick. But castor fuel & gunk has amazing permanent gluing properties.

 

[tornitore45]

I did not really mean "pounding" literally but ball bearing are supposed to be hard to slide on the shaft and off their seats, so some kind of gradual pulling is necessary.

If I read the plan correctly the fuel suggested is 3-5% Nitro but it does not say anything about oil.
Being pumped lubrication there should be no need for oil in the fuel or no more than 2% just to be safe.

I have researched the fuel availability and found specifications to be wanting.
Some say is for 4 strokes. Does that imply no Oil?
There are 4 strokes with fuel passing through the crankcase, that would require oil.
Could not see any Low Nitro fuel, it starts at 10%.

When we get to running these engines we may want to pool resources to share a gallon of fuel. I do not plan to run the engine more than a few time fur fun. No Airplane for me.

 

[petertha]

The Edwards is a bit different than most commercial glow engines. My understanding is straight methanol is the 'fuel'. The separate lubrication pump predominantly directs oil to key areas, but one could expect carryover film to other critical areas. Nitromethane added to methanol is helpful for starting & idling & adds power as long as the CR & timing is conducive. I think the Edwards lube circuit has been discussed elsewhere on the forum, you would have to do do a keyword search. My radial is a bit different, oil bath in the nose case to keep the gears happy & regular RC 4S fuel that gets inducted into the crankcase rear for the rod assembly before going out again to the heads.

Typically when you see commercial glow fuel for 4 strokes, they will specify their recipe like: oil content 18-20%, majority typically synthetic & remainder castor (80/20 for example) and nitromemthane content (anywhere from 5-30% application specific). The remainder is methanol +/- mystical magical goodies like anti-corrosion, anti-foaming agents or whatever. Of course there are as many opinions of the best fuel as there are engines. My experience has been the 4S blends are appropriate. Sport fuels, loosely meaning 2-stroke fuels, may have slightly lower oil content & may or may not castor. 4S can actually run a bit hotter on the exhaust side even though firing half the stroke cycle. I think the view is that bit of extra oil helps with heat & gets in the mechanical nooks & crannies like rockers & pushrod/valve interfaces that just aren't there in 2S. Some amount of castor seems persistent over the years so there must be a good reason, its always present in racing fuels.
https://vpracingfuels.com/product/yssaito-2020-stroke-20-oil/
https://vpracingfuels.com/rc-fuels/#nitro
http://saito-engines.info/fuel.html
https://www.rc-airplane-world.com/rc-glow-fuel.html

 

[mu38&Bg#]

A 10° taper is self releasing in theory, maybe less so with soft materials. Regarding cam gears, the prints are odd in that the gears are not clocked at all. The gear train should be clocked and the gears fixtured such that holes are drilled in proper locations.

Try a hobbyshop in Austin for glow fuel. They may even have quarts. In Austin it may not be common , but gasoline "antifreeze" or deicer for the fuel tank is methanol "Heet". https://www.goldeagle.com/product/heet-gas-line-antifreeze-water-remover/

 

[petertha]

That's why I was saying there may well be different or better permutations of how to clock it in depending on whats easiest to do. If the cam ring+internal gear assembly were pre-locked and the crankshaft gear was pre-locked, you still have one degree of freedom with the idler gears. Meaning you could rotate the cam assembly & it would just spin the idler gear than engages the internal gear.

OTOH if you lock the crankshaft gear, idler gear set, then you need to have some means to alter the cam phasing relative to the ring gear because all the gears are now engaged & locked between themselves. I'll take some pics when I get to this stage but my engine may not be 100% comparable. Would be better to hear from an Edwards builder who went through the process.

 

[mu38&Bg#]

Ah, that's right! The idler assembly should let you set the timing were you want it. No clocking of any gear is required. The error would be very small in any case.

 

[tornitore45]

The problem is not "Where" the slip-clocking-pahsing or whatever one calls it.
The problem is the "How" Once the proper relationship of meshing teeth and relative position of the idler pinions is determined, the engine needs to be disassembled without disturbing the setting and the idler pinions Loctited to the shaft in the same position. At least one of the pinions needs to be slipped off the shaft to add the Loctite and then pushed back on in the same position. The system has to allow some frictional slippage to adjust it but stay put from the time the engine is disassembled to the time everything is locked in its permanent position.
Using ovalized holes on the cam does not pose the problem of disturbing the position, just tighten the screws where they are already.
Either method requires to have either the cam or the crankshaft immobilized and the other free to adjust. There is no current provision to immobilize or rotate the cam relative to a locked crank.

 

[mu38&Bg#]

That's the beauty of the "idler assembly"( I thought these were called trunnions). Look at how the teeth align between the two gears. The teeth align at a 0° and 180°. By pulling the gear assembly and turning it one tooth you changed the cam phasing. Between that and advancing/retarding the cam itself one tooth you a lot of adjustment.