Open thread on Edwards 5 Radial

[tornitore45]

Just fro kicks
Here the difference between Pinions and Trunnions
https://en.wikipedia.org/wiki/Pinion
https://en.wikipedia.org/wiki/Trunnion

 

[mu38&Bg#]

I guess compound gear is a common term. A place I worked at (Barber Colman should ring a bell with gear heads), called them trunnions.

 

[petertha]

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.

Re the ovalized holes idea - you are saying the nose case is temporarily omitted while phasing the cams? Otherwise I cant see how you set the adjustment with nose on. I originally assumed the case needed to be present in order to detect the lifters being actuated but maybe there is a way to set up DTI on the lobes themselves and or scribe between cam beginning or midpoint or something. The critical bit is knowing cam phasing relative to piston position. You need that relationship in order to ensure correct valve open/close. For example maybe piston is first set at TDC indicating beginning of intake stroke, THEN set cam plate indexed to a known position relative to I/E lobes. Seems to me that mine is exactly midway cam lobes at TDC but purely a function of opening & duration on that engine. Otherwise if you FIRST set the cam based on beginning of lift or maximum lift, then you would have to have a protractor on the crankshaft to set it to some odd angle or know distance the piston as above/below TDC. Its like an X & Y coordinate, just one is not enough.

Re your last sentence, the cam+ring gear can rotate unconstrained & independent of the crankshaft so long as the idler gear which engages the ring gear is not yet locked to its mate gear (trunnion or whatever its called). The method I was mulling is just some Loctite or slow cure epoxy between gears. You have X amount of time to phase the assembly, then allow to cure, then the gear sandwich is preserved for disassembly & mechanical pinning. During re-assembly, there can only be one unique gear tooth position to put Humpty Dumpty together again if you reproduce the TDC & cam event properly again. At least that's what my simple brain is anticipating LOL

 

[tornitore45]

Lots of good ideas guys. I did not consider the fact that the nose can be off. Since the cam lobe Max. lift is exactly on center-line it makes for an accurate place to line up the indicator. Both of the idle shaft gears must have a specific tooth engagement with the crank and the ring. In other words 4 dots one on each gear to line up.

 

[tornitore45]

I distilled some information from the cam lift table:
The lobes are symmetrical about the point of max lift, exhaust and intake are slightly different
Exhaust Starts @ 121 degrees Then again @ 301
Exhaust Peaks @ 152 degrees @ 332
Exhaust Ends @ 183 degrees @363
For a duration of 62 Cam degrees or 248 Crank degrees.
Assuming to set for max lift at mid stroke on the way up the valve opens 32 degrees before BDC and closes 32 degrees after TDC

Intake Starts @ -4 degrees Then again @ 176
Intake Peaks @ 25 degrees @ 205
Intake Ends @ 54 degrees @234
For a duration of 58 Cam degrees or 232 Crank degrees.
Assuming to set for max lift at mid stroke on the way down the valve opens 26 degrees before TDC and closes 26 degrees after BDC

Valve overlap is 9 Cam degrees or 36 Crank degrees
Valve lash will reduce all duration's slightly.
All of these number seem very conventional

I think I will set mine to max exhaust lift for the crank at 90 degrees before TDC.

 

[mu38&Bg#]

If I get really bored I'll draw the gears and cam in SW and clock them.

 

[Glorfindel]

I distilled some information from the cam lift table:
The lobes are symmetrical about the point of max lift, exhaust and intake are slightly different
Exhaust Starts @ 121 degrees Then again @ 301
Exhaust Peaks @ 152 degrees @ 332
Exhaust Ends @ 183 degrees @363
For a duration of 62 Cam degrees or 248 Crank degrees.
Assuming to set for max lift at mid stroke on the way up the valve opens 32 degrees before BDC and closes 32 degrees after TDC

Intake Starts @ -4 degrees Then again @ 176
Intake Peaks @ 25 degrees @ 205
Intake Ends @ 54 degrees @234
For a duration of 58 Cam degrees or 232 Crank degrees.
Assuming to set for max lift at mid stroke on the way down the valve opens 26 degrees before TDC and closes 26 degrees after BDC

Valve overlap is 9 Cam degrees or 36 Crank degrees
Valve lash will reduce all duration's slightly.
All of these number seem very conventional

I think I will set mine to max exhaust lift for the crank at 90 degrees before TDC.

Nice infos, thx. Im programming the cam.

 

[petertha]

Its been a long while since I looked at this & I never ended up building the Edwards, so take my spreadsheet with grain of salt. Anyway what I think tornitore45 has done is similarly mapped the intake & exhaust cam durations, max opening position etc. Hopefully they match mine, but leave that aside for the moment. Because the cam lobes are machined on the same part according to the table in the plans, this also fully defines the intake / exhaust phasing relationship to one another.

But there is still one important parameter: depending on how you clock the cam plate relative to piston position, all other timing events follow as a byproduct. Again, its been a while, but I don't recall seeing this defined. For example we would be looking for something like 'inlet opens at 20 degrees BTDC". If that's where you set it, fine. Just know that every other timing event (intake valve closed, exhaust valve open & close) all become defined, or locked down if you will due to the fixed geometry. And so it goes - if you adjust IO to 10 deg or 15 deg, then remaining parameters follow along. So, have you guys seen a reference timing event like this stated anywhere?

I think I will set mine to max exhaust lift for the crank at 90 degrees before TDC.
^^ what is this based on? ^^

I did look into several commercial methanol 4S engines of similar displacement & timing can vary quite a bit. Fortunately the engine I'm building has this a bit more clearly defined.

 

[petertha]

If I get really bored I'll draw the gears and cam in SW and clock them.

That would be great. But another consideration that might be simpler & arguably more useful is SW sketch with the key components defined as block elements. That way you could alter the cam relative to piston & then easily measure / compute all other timing events as a direct result. Gears would just be (toothless) pitch diameter circles that define the various gear ratios (crank gear > idler-1, idler1>idler2, idler2>ring gear). More importantly, you would also have the crank rotation relative to cam in this block assembly, so that defines piston position at any rotation angle & therefore its relationship to cam event.

That's what I was aiming to do in spreadsheet form. I think I succeeded on a more recent one, but its still clunky. In SW you could rotate to any desired angle & all other parameter dimensions would be revealed. This would aid in setup. Drawing the gear teeth themselves aren't even important unless you did the whole enchilada & defined 'tooth to part' for every component involving a gear.

 

[tornitore45]

The plans do not say how or where to time the engine. That is why we have this conversation. I did exactly what petertha suggested for my Hoglet which I completed today and will run the first sunny day.
Made a spreadsheet, for each degree of crank it calculated the degree of each of the three cams, a common offset angle can be added which accounts for slipping the gears.
The Hoglet plans do not specify the phasing either.
Looking at the cam table is not immediately apparent what goes on, I plotted the lift versus angle for all lobes and made a diagram, then things become instantly clear.
If anyone knows how to post an Excel file I would share it.

 

[petertha]

I found a tabulation I put together some time ago. Not suggesting this is appropriate (or 100% reliable).

 

[petertha]

The Ohrndorf 5-cyl radial works out to this

 

[tornitore45]

Good info. The Ohrndorf diagram looks like has the direction of rotation wrong. Valves close before opening.

 

[mu38&Bg#]

The cam lobes as described in the profile chart are symmetric about TDC. That is intake open and exhaust close occurs the same angle from TDC on their respective sides. This is easily observed by rocking the crank about TDC and indicating lift on the followers. This is the most common configuration in model engines as peterha has shown.

Valve timing is not that critical. When you have engines with tuned intake and exhaust tracts, then timing is much more critical to the power band.

 

[petertha]

Oops, I messed up the rotation symbol didn't I? Crankshaft = CCW. Idler gears 1&2 = CW. Ring Gear = Cam = CW.

 

[petertha]

Another consideration is the the Edwards lifters are on a common center plane relative to cylinder. My engine has them offset, radially angled. Again, this will come out in the physical alignment clocking but another general FYI. Sheesh, I better go back to my notes to see if I factored that correctly on the timing degrees.

 

[josodl1953]

The original Edwards had offset lifters too. I suppose Robert Sigler put them both on center to make timing easier.

Jos

 

[petertha]

I did some more CAD work last night & came to the realization I didn't arrive at the end of my journey with a complete understanding of cam phasing when I paused on the project last year. This is more generic radial engine cam timing discussion as opposed to Edwards specific, but the exact same principles will apply.

More for fun than any real revelation, I made the 4 gear train as 'block' elements. This allows one to rotate the crankshaft gear to any desired increment & observe/measure the effect on the ring gear. Now if you take this one step further & draw the cam bumps on the ring gear & superimpose a master rod, you can see the whole dynamic. This tool might be useful if you wanted to determine a relationship that was more convenient to measure in real life. For example where is piston when indicator is at midpoint of intake bump. But it gets quite busy & convoluted seeing what lines correspond to what. And as we discussed everything revolves around how you first align the I/E cam plates to begin with.

 

[petertha]

So I went back to my original method which is basically stacking the cam plates together in an assembly. The idea is to superimpose some reference datum(for example TDC) onto the assembly & then pick off radial measurements to whatever you want to know. Then multiply by the gear ratio (4 in my case) & that yields crankshaft timing degrees. You don't really need the gear tooth positions but I guess it could be accomplished in a (more complex) assembly model.

The last bit is to superimpose the appropriate I/E lifter positions because as we have seen, they may not be centered to the cylinder. ie. you need to measure from intake lifter position to intake cam event & exhaust lifter to exhaust cam event. Particularly if the I/E lobes are unique to each other. I now see in my case I misunderstood the designers timing TDC comment about midpoint between lobes. See what you guys think, is this a better way?

 

[tornitore45]

In my opinion the original version with the poppets off the center-line is a lot more pleasing. For one it reduces the poppet-pushrod-rocker angle a possible safety against a pushrod jumping out at Hy-Rev.
Hope the relative position of the two cam sets was altered to compensate.
I am debating with myself whether to folllow the plans or try to duplicate the original look. While the staggered push rod requires a bit more alertness during machining it does not add to the complexity of timing the cam. We set one valve (intake for example) for one cylinder and all the rest ( exhaust and other cylinders) follow in place.

To be sure, we are all talking about phasing the master cylinder, in a radial all other cylinder may be off a tiny bit from what the master is experiencing as timing goes.