# Edwards radial questions



## kylenlord (Feb 2, 2020)

Hey Everyone, I have a couple of random questions about the Edwards radial five engine. I’m hoping to get some feedback. 

I’ve heard of people concerting this design to run off gasoline. What would be involved with that? Does it involve a distributor or is it one Hall effect sensor and a wasted spark setup? Would gas or methanol have more power?

Could the displacement of the engine be increased? I’d think it would a matter of either increasing the bore or increasing the stroke. I would think that increasing the stroke would have less drastic affect on the overall design but how does stroking effect the overall performance of the motor? 

I’m thinking about getting back on the engine come spring time, I’ve improved the shop setup since I set mine aside and am really looking forward to it.

Thanks 
Kyle


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## tornitore45 (Feb 3, 2020)

A wasted spark ignition system wont work on a radial 5.
You need a distributor 
OR 
5 separate ignition "Channels" each triggered by its own Hall sensor.
All sensors on a pentagon around one spinning magnet.


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## Cogsy (Feb 4, 2020)

tornitore45 said:


> A wasted spark ignition system wont work on a radial 5.
> You need a distributor
> OR
> 5 separate ignition "Channels" each triggered by its own Hall sensor.
> All sensors on a pentagon around one spinning magnet.



I've heard (but never actually seen) that wasted spark can be used on Harley-type engines with 60 degree (maybe even the 45 degree?) V's without issue. So I'm guessing it's not the separation of the cylinders that is the issue. Is it just the issue of getting 'enough' spark to jump 5 gaps at once that is the problem?


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## tornitore45 (Feb 4, 2020)

Cogsy, to have the 5 gap in series you need spark plug isolated from the metal head.
Waste spark is only possible in 2 cylinders engine because the HV is applied from tip to tip. All plugs have the threaded part in common.
Also wasted spark is possible IF one of the cylinder, the one that is not firing, is 360 equivalent crankshaft degrees or nearly so from the ignition point.
One cylinder at TDC compression stroke and the other somewhere around TDC staring the intake stroke.  A spark at the beginning of the intake is "wasted" because there is nothing to ignite but exhaust residual.
I have built the Hoglet which is similar to a Harley 45* and it works fine with a wasted spark.   The two cylinders are 360  +/- 45 equivalent crankcase degree apart.  They are physically 45* impinging of the same crank and cammed to work 360* apart.    While one piston is TDC the other is either almost done exhausting or just beginning the intake.  Yo want the wasted spark to go at the exhaustion one because there is nothing to burn there.


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## Cogsy (Feb 5, 2020)

Oh, I was under the impression the Hoglet fired "one-after-the-other" and I've heard incidental reports of wasted spark working in such a situation. I assumed the lack of compression on the cylinder that's not near TDC prevented ignition of the partially compressed charge. Obviously I could easily be mistaken.


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## tornitore45 (Feb 5, 2020)

You made me think about the firing order of the Hoglet.
The magnets on the camshaft are nearly 180* apart (not exacly 180 because the cylinder are 42* offset).   A new spark comes every nearly 360* of crankshaft, therefore the firing is alternate 
Fire-Turn-Fire-Turn   rather than   Fire-Fire-Turn-Turn
When I was building the Hoglet I was trying to find out what a real Hearly Davison is timed but never got a straight answer.
It would seem to me that a Fire-Fire-Turn-Turn cycle would make a pretty unbalanced engine and a lousy design just to save one coil.


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## Cogsy (Feb 5, 2020)

I thought the weird firing was part of what gave Harleys their unusual sound. I know my father has a 2 cylinder tractor that fires one cylinder straight after the other but I don't know why they designed it like that, surely not just to save an ignition component.

Edit to add: I found some info on Harley timing. It seems like the 'normal' firing interval for a 90 degree V is 315 degrees then 405 degrees which provides the unusual sound, while there are alternate cams available (I think for racers) which convert 45 degree V's to 45/675 and 90 degree V's to 90/630. Supposedly this gives the rear wheel nearly 2 crankshaft revolutions to grab traction between hits of power. Possibly this was the idea behind the tractor design as well. Sorry for drifting so far off-topic!


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## awake (Feb 5, 2020)

Cogsy said:


> I know my father has a 2 cylinder tractor that fires one cylinder straight after the other but I don't know why they designed it like that, surely not just to save an ignition component.



That sounds like the old John Deere engine, often called a "Johnny popper." Here's what I've heard for the reason for the fire-fire-turn-turn pattern, at least for that engine: Since the cylinders are side-by-side, a fire-turn-fire-turn pattern would require both cylinders to move in the same direction at the same time. Since the cylinders are large and the throw is long, having the cylinders move in unison would generate a lot of vibration. Instead, the cylinders move in opposite directions, so that the TDC for one cylinder is 18o° apart from the other.

Supposedly John Deere was very proud of how smoothly the engine ran - people would hear the distinct "Johnny popper" sound and think it must be vibrating like mad, and then they would balance a nickel on edge on the hood and show that it would not fall over. Or something like that ...


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## petertha (Feb 6, 2020)

I haven't seen the Moki 5-cyl radial up close but it has a spark ignition system (proprietary to their engine).
https://www.aeroscale.shop/collections/moki-engines
Some partial assembly pics 
https://www.rcuniverse.com/forum/rc...8946260-moki-radial-care-maintenence-135.html
Sorry I don't know much about these engines other than they exist

CH always seems to get mentioned for multi-cylinder conversions & retrofits
https://www.ch-ignitions.com/5-cyli...-for-moki-s150-moki-s180-rcs-150-rcs-180.html
https://www.rcuniverse.com/forum/gas-engines-142/11624029-ch-ignition-moki-150-radial.html


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## Billitmotors (Nov 23, 2020)

In July 1986 I purchased a set of drawings from Forest Edwards for his 5 cylinder radial engine. I started to build a pair of these engines but found a problem with some of the parts that I made and at the time shelved them until I could come up with a fix for the mistake. Any how I solved the problem and have continued on with the engine again. Since then I have found this site and I was wondering have there been any updates to the drawings as I have seen a number of photographs showing modifications to this engine? I have since made 36 other engines and thought it was time I finished this pair of engines.


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## tornitore45 (Nov 23, 2020)

I got my plans free   here

www.grabcad.com
you need to register

The plans I have show NO errors they are drawn by Robert Siegler
All sheets are revision A00 except
Sheets 10/36; 12/36; 22/36; 28/36; 34/36 are revision A01

Sheet 26/36 is revision A02

Edit:     I try to find it on grabcad but today could not


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## petertha (Nov 23, 2020)

I think I got mine off the old R&R yahoo site back in the day. Maybe its still around? Mauro built one recently so good he provided revision numbers as guidance. Is there a way on grabcad to specifically search for the PDF files as opposed to 3D versions? I never really trusted them many/most are 3D models. Not that there is anything potentially malicious but hard to know what version they used or drawn/assembled correct.





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## tornitore45 (Nov 23, 2020)

The plans have no copywrite claim on it.   Edwards made them publicly available, for which we thank him.
So there should be no objection to share them.
Here they are


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