Starter for radial engine (Edwards 5)

[DiegoVV]

Dear friends,

I've just finished my Edwards 5 radial build (pictures soon). I've still have not done its firtst start and now I'm debating myself on the best way to do it.

With the prop installed it takes some effort to turn it by hand due to the amount of compression....it does, but not as freely as I expected.

How do you start a radial engine? By hand (Hard and risky) or using an electric starter? If I use one, can you recommend something with enough torque?

Disclaimer: The base is provisional, used for assembly purposes, I'm building another one with steel and carbon fiber for the bling factor.

 

[stevehuckss396]

Get a starter like this one. I have had a tower hobby starter for years but they don't have them anymore. The link I sent is a heavy duty high torque unit. I would shy away from the 20 dollar models due to you actually needing some grunt to get your engine spinning.

https://www.towerhobbies.com/product/powerpro-hd-12v-starter/HAN162.html

 

[cwelkie]

Another option is to make a "Hucks starter" style of hub that can be driven by a matching dog in a drill/driver. It provides a very solid connection that disengages easily once the engine starts. I've used this approach to good effect on 1/4 scale Cirrus and Anzani engines. Of course, this may not be the easiest solution given that your prop hub does not use a bolt together propeller carrier or hub

Steve's recommendation is a good one. Please ensure that the starter drive cone is a good fit on the propeller spinner. If mismatched the drive will not be solid and there is a high likelihood of the starter "jumping off" - potentially into the propeller arc.

 

[DiegoVV]

Thank you both for the inputs!! I think I'll visit my hobby store to buy a good starter based on Steve's advice. I thini I'm too lazy for designing and machining a new prop hub to use Cwelkie's approach, although I'll consider it seriously for my next project

 

[stevehuckss396]

Does anybody else find it funny that someone named Steve Huck has never heard of a hucks starter?

 

[cwelkie]

Does anybody else find it funny that someone named Steve Huck has never heard of a hucks starter?

That is funny! I guess you haven't been spending enough time in vintage "aeroengine world".
They were a very innovative response to "there has to be a better way".

https://simanaitissays.com/2021/11/13/b-c-hucks-maarvelous-starter/
Charlie

 

[stevehuckss396]

I'm working on a pair of 9 cylinder engines. They are both getting one!

 

[petertha]

I've been thinking about this issue myself for my own 5-cyl radial. I've used conventional RC starters quite a bit on both 2 & 4-strokes, but only single cylinder. I think the electric motors like on the Sullivan & similar are kind of wound to 'spin'. I just have a gut feel that more torque at the expense of rpm might be more suitable for a radial. I remember one of the guys at the field had a multi-cylinder OS & he used this kind of starter, also 12V.

https://www.kavanrc.com/en/item/planetary-gear-starter-12v-109381

 

[petertha]

Very clean looking build. Look forward to the posts. PS - what carb did you select?

 

[Tim1974]

I would try hand starting it I have a 9 cylinder and was very surprised at how easy it is to start all thow I do give it a quick spray of aero start then a quick flick and off she goes

 

[DiegoVV]

Very clean looking build. Look forward to the posts. PS - what carb did you select?

Hi Petertha. From my old days in the RC Car racing scene, I have several carburettors, most of them seem to be better made than the standard Perry. This is a carburettor from a Sirio 1/8 on-road engine.

 

[Steamchick]

Hi guys, I just picked-up this thread as I once was responsible for starter motors on 1.0l to 2.0 l car engines, for a major motor manufacturer.
Pre-1990 convention was a series DC motor - for high torque at low rpm, due to the full current passing through the field coils giving a large magnetic field for the same current through the armature to react against.
But Post 1990, Permanent magnets became so powerful with "new" rare earth technology, that the high speed PM starter became a sensible and cheap motor, but only delivered 12 to 1/3rd of the torque. So starter motors changed design to include planetary gearboxes to reduce the speed/increase torque proportionately. The Noise that the customer heard was the biggest problem with "new" starter designs, but this technology happened at the same time as hand tools, vacuum cleaners, and thousands of other products changed with the new magnet availability, and cost convinced everyone they were better solutions.
What I suggest for the starter for the radial engine is a bit of design work...
Take a dial torque wrench and use it to measure peak torque when you wind the engine around by hand.
Then multiply by 100 (for 100rpm) to get the power you need from the starter motor. Then all you need is a motor that can adequately provide that torque at 100 rpm and you have a solution.
It is rather more complex than that due to gas dynamics and heat flow, etc. from compressing gases in the cylinders, but your selected motor is likely to develop twice the torque and power than the calculations anyway, so that should work well.
Friends at the local Model Engineering club use hand drills for starters... with simple cone and pin quick release connectors on the Prop. nose. (battery screwdrivers are too slow).
K2

 

[josodl1953]

Hi Diego,
Please note that radial engines can have a hydraulic lock when there is too much fuel and/or oil in the lower cylinders. So, if you experience a very "high compression" feeling it may help to turn the prop backwards a few times or remove the glowplugs to get rid of the excess fluid in the combustion chamber(s). I remember seeing props turned by hand ( in old war movies) before starting when radial engines had been standing idle for a long time.

Jos

 

[Vixen]

Hi Diego,
Jos is quite correct about clearing any drained oil from the lower cylinders. Years ago, I worked on aircraft fitted with Bristol Hercules sleeve valve radials. Every morning we had to 'walk' the engine through eight blades (two complete revolutions) of the prop, before attempting to start the engines. There was usually a great cloud of oil smoke as the engine cleared it's throat.

Mike

 

[Bentwings]

Dear friends,

While I’m sure it takes some torque to start these I used a padded leather welding glove on the larger Rc flat twins an bigger singles . Generally the “ slap method” works best . Turn it over byby hand with ignition off . The “ impeller supercharger” won’t do much mixture mixing until it starts don’t expect boost . There have been many attempts at centrifugal blowers and superchargers but size and air flow just doesn’t work out . There was even a compounded one . It would inflate a plastic bag. It will really thrash the fuel air once the engine is running . Most radials start pretty easy if you look at some giant scale Rc Warbird videos you can see some pretty good sized radial engines starting comp ARF is a good Corsair model to watch these are 50 pound airplanes the radials make about 15 hp 34 to 36 inch props some three and 4 blade

I've just finished my Edwards 5 radial build (pictures soon). I've still have not done its firtst start and now I'm debating myself on the best way to do it.

With the prop installed it takes some effort to turn it by hand due to the amount of compression....it does, but not as freely as I expected.

How do you start a radial engine? By hand (Hard and risky) or using an electric starter? If I use one, can you recommend something with enough torque?

Disclaimer: The base is provisional, used for assembly purposes, I'm building another one with steel and carbon fiber for the bling factor.

 

[Bentwings]

. Try tower hobby or horizon hobby . There are new ones with planetary gears that have a silicone cup hub so you could use a spinner there are at least two sizes of starting cups. The original starter used a tooth belt reduction but I YHINK the new ones have much stronger motors these are 12-24 volt units I’ve watched many nicecradials hand started a two blade prop is probably safer than 4 blade I’ve used all on my two stroke singles and flat twins I’d turn it over ignition off a number of time I used a hard “ slap” with padded welding glove You have to “mean business” when Han d starting the 18 cyl will probably fire two or three cyl starting but no single cyl firing will be strong enough to “bite” my Rc engines all used 24” props. Regardless of number of blades .
Thank you both for the inputs!! I think I'll visit my hobby store to buy a good starter based on Steve's advice. I thini I'm too lazy for designing and machining a new prop hub to use Cwelkie's approach, although I'll consider it seriously for my next project

 

[josodl1953]

Hi Diego,
How about this:

Just a piece of wood with a piece of bicycle tube wrapped around it. I remember seeing R/C flyers starting their 10cc's with something like this, back in the sixties. With a 5 cylinder engine, you have only one cylinder on compression at the time, which means 12 cc for a full-size Edwards ( total 60 cc).
Should not be too difficult, I think.
Oh, by the way, the Edwards does not bite you, just stay clear of the prop once it's running.....

Jos

 

[Bentwings]

Hi Diego,
How about this: View attachment 139538
I tried the “stick” method very early on in big Rc engines . It wound up in the drainage ditch next to the field after I removed the padding. In our club at the time you ere looked down upon if you did not glove hand start gas engines. I can’t recall anyone getting “ bit”. You can’t just flip props like glow engines many gas engines have magnetos thatcrequire about 400 rpm to start. That is one smart smack on the prop those newer engines that have electronic ignition are not as critical. But you still have to spin the prop pretty fast. Not sure why . The main thing is get the prop and sensor through the firing sequence . Somevengingines take proper positioning . It may seem awkward but when you look at it analytically you can see that this gives maximum rpm through the firing sequence . Bottom line is don’t “ baby” prop flipping . You need to make it know you are boss. I have several notorious hard starting engines and I flew these for years choking until pops then turn off choke and one stroke starting . Even the twin took only a minimum of flips
Just a piece of wood with a piece of bicycle tube wrapped around it. I remember seeing R/C flyers starting their 10cc's with something like this, back in the sixties. With a 5 cylinder engine, you have only one cylinder on compression at the time, which means 12 cc for a full-size Edwards ( total 60 cc).
Should not be too difficult, I think.
Oh, by the way, the Edwards does not bite you, just stay clear of the prop once it's running.....

Jos

 

[petertha]

Hi @Bentwings I'm not sure if you realize - but in your recent posts 15, 16 & 18 for example, you are just quoting another post (as opposed to replying with some text of your own).

 

[Bentwings]

Hi @Bentwings I'm not sure if you realize - but in your recent posts 15, 16 & 18 for example, you are just quoting another post (as opposed to replying with some text of your own).

it’s entirely possible and I apologize . I have a very hard time with the spell check editor both for combining things that should not be and not really correcting as it should it’s hard enough to just post with my personal vision issues . Sometime I should just read and keep opinions to myself . I’m just really interested in what others are doing that I cannot I try to respond if I think I can help . This “corrector” is very intolerant of a simple missed space . It then will run a bunch of text together . I try and edit but even this does not always stay fixed . I’ll try and limit my comments to minimum . I’m not sure how the double post came about sometimes the post reply operates slow especially in the evening .

Thanks for understanding I appreciate notice if I make errors or mistakes .