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Engine basics => Engine set up tips => Topic started by: Gary Dowler on June 16, 2017, 06:07:45 PM
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Just picked up a used K&B 40 r/c at an estate sale. It was stiff from sitting and no glow plug so no way to test compression. Owner was obviously not available for comment. Get it home and cycle some fuel through it and got it turning freely again. Stuffed a glow plug in it and viola! No compression. Ok, I know the piston ring can stick after years of no use. It was suggested to let it sit with fuel in the cylinder overnight. Did that, nothing. Did the same with a penetrating oil, same result. It was suggested that I heat the motor well with a heat gun, nothing. Tried starting it today and, amazingly, actually got it to run for about 2 minutes. Sounded ok too. fuel ran out and flipped the prop expecting compression, still almost nothing. Very little changed from when I got it.
Not sure when it was made, s/n is 0072695. Im thinking a new piston ring, perhaps new cylinder liner. Thoughts, suggestions?
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A Dyke's ringed engine will be just as you explained. The compression is gained by flipping the prop abruptly or using a starter. The ring is on the top of the piston and uses the compression to spread the ring to the cylinder wall. If you flip slowly, it just feels dead, but when flipped it should offer a fairly good snap. This is of course doesn't mean that it's not tired I'm just stating a possibility. I have a few K&B .40's which indeed are the ringed type I explained but I'm aware that other models had different configurations and I'm not certain of yours. Ken
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Just picked up a used K&B 40 r/c at an estate sale. It was stiff from sitting and no glow plug so no way to test compression. Owner was obviously not available for comment. Get it home and cycle some fuel through it and got it turning freely again. Stuffed a glow plug in it and viola! No compression. Ok, I know the piston ring can stick after years of no use. It was suggested to let it sit with fuel in the cylinder overnight. Did that, nothing. Did the same with a penetrating oil, same result. It was suggested that I heat the motor well with a heat gun, nothing. Tried starting it today and, amazingly, actually got it to run for about 2 minutes. Sounded ok too. fuel ran out and flipped the prop expecting compression, still almost nothing. Very little changed from when I got it.
Not sure when it was made, s/n is 0072695. Im thinking a new piston ring, perhaps new cylinder liner. Thoughts, suggestions?
This engine uses a Dykes ring, which has very little tension and very little compression when you flip it. It seals up when the engine fires which pushes the top edge of the ring out to create the seal. It's normal not to have much compression.
Run it fast with a small prop at normal speeds (normal RC speeds, that is, an 8-6 or so with the throttle wide open, and the needle peaked and then backed off just enough to make sure it is not sagging) a few times (maybe a quart or so) . Use a fuel with a lot of synthetic, but a little castor. If it seems to run OK, then you will have to assume it's good until proven otherwise.
Brett
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Interesting, and thanks to both of you for the replies. I've never owned a engine like this, so this is new to me. When I got it running it sounded pretty normal (only prop I had to throw on it was a 10/6.). Only fuel I had on hand is 5% with 18% blend of synthetic and castor. It actually has more castor because I added more to run my Fox engine properly.
Should this engine have any form of head gasket? It has nothing as it is.
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K&B's generally didn't use head gaskets (or front & rear gaskets) after the "Series '61" engines. Which were not very good, frankly. They eventually got them working fairly well in about '64 or so.
I believe that engine is a model #4050, but I've never had one. I did have a #4055, which was a CL version, and was an ABC. Brett is right about the Dykes ringed engines. If you take it apart, check for cylinder bore gouges from the wristpin. We found that problem around '67 with one we used for rat racing. They really needed a rebuild every year, including piston, cylinder, ring, rod, wristpin & pads. Not real impressive durability, but it was a sweet engine with great restarts (with a good ring). You might be able to get a better ring from our piston ring supplier, down in the vendor's forums.
I went to HS in Pullman with a Dowler...Viki...another USAF brat. Any relation? H^^ Steve
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If it has four ' windows ' in the sleeve , at the exhaust port , its Ringed . One Big Hole is A.B.C. .
The A B C R/C & C / L are the same basic unit .
IRVINE 40 RINGS fit , gudgeon & rod too . The Irvine Ring seems a bit tougher .
A 10 x 6 is good , for 90 mph .a 11 x 5 would be o.k. for aerobatics , rich .
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K&B's generally didn't use head gaskets (or front & rear gaskets) after the "Series '61" engines. Which were not very good, frankly. They eventually got them working fairly well in about '64 or so.
I believe that engine is a model #4050, but I've never had one. I did have a #4055, which was a CL version, and was an ABC. Brett is right about the Dykes ringed engines. If you take it apart, check for cylinder bore gouges from the wristpin. We found that problem around '67 with one we used for rat racing. They really needed a rebuild every year, including piston, cylinder, ring, rod, wristpin & pads. Not real impressive durability, but it was a sweet engine with great restarts (with a good ring). You might be able to get a better ring from our piston ring supplier, down in the vendor's forums.
I went to HS in Pullman with a Dowler...Viki...another USAF brat. Any relation? H^^ Steve
Very interesting! I'll have to look into any Viki's in the family. Most of the family is from Montana.
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If it has four ' windows ' in the sleeve , at the exhaust port , its Ringed . One Big Hole is A.B.C. .
The A B C R/C & C / L are the same basic unit .
IRVINE 40 RINGS fit , gudgeon & rod too . The Irvine Ring seems a bit tougher .
A 10 x 6 is good , for 90 mph .a 11 x 5 would be o.k. for aerobatics , rich .
It's got 4 ports. I did see online that rings, pistons and cylinder liners are available. I did a check and there is still virtually no compression no matter how fast that prop if flipped. I'm certain that this one is just worn out.
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It's got 4 ports. I did see online that rings, pistons and cylinder liners are available. I did a check and there is still virtually no compression no matter how fast that prop if flipped. I'm certain that this one is just worn out.
Maybe, but *you will not get much compression with hand-flipping*, worn out or not. It just doesn't work that way, it requires the pressure of an actual firing (150-ish PSI and up) to do much with the seal. That is a flaw for our purposes, because you can't really tell whether it is worn out or not without actually flying it in a stunt plane.
If you can get it started reliably, it's probably good enough to get some flights in.
Brett
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Just picked up a used K&B 40 r/c at an estate sale. It was stiff from sitting and no glow plug so no way to test compression. Owner was obviously not available for comment. Get it home and cycle some fuel through it and got it turning freely again. Stuffed a glow plug in it and viola! No compression. Ok, I know the piston ring can stick after years of no use. It was suggested to let it sit with fuel in the cylinder overnight. Did that, nothing. Did the same with a penetrating oil, same result. It was suggested that I heat the motor well with a heat gun, nothing. Tried starting it today and, amazingly, actually got it to run for about 2 minutes. Sounded ok too. fuel ran out and flipped the prop expecting compression, still almost nothing. Very little changed from when I got it.
Not sure when it was made, s/n is 0072695. Im thinking a new piston ring, perhaps new cylinder liner. Thoughts, suggestions?
you can increase compression and ease of cranking two ways, first get a new sleeve , and buy a new ring from the guy who bought Frank Bowman's company, tell him you want one with a tight gap (Izero gap) the open the gap up to .001, break the engine in very slowly, running in a fat slloppy 4 stroke for 6 to 8 runs, the start slowly speeding the engine up, you will wind up with a motor you can hand start. the other way is to buy a ABC lapped piston/sleeve setup, they will have huge compression and a very good start.
regards
Randy
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Gary DO NOT buy your ring from MECOA unless you want no compression and a very large gap.. I have a dozen here brand new that ALL have huge gaps, The only way to use these in CL is the way Stan Powell did, he sent his sleeves to Henry for chroming, and in doing so make the diameter smaller, this made the end gaps much tighter, and so they were usable, and had compression to hand crank. My ST dykes Engines OS dykes engines and my K&B 40 all have decent compression for hand starting
So get a ring that you can buy with a small or no gap new, that way you can set the gap tight... starting off at .010 thou is NO good
If , as Motorman says, the new guy doing Frank's rings are no good, not round and rough, then I am afraid we will have to look for others to make Dykes rings for us.
Randy
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you can increase compression and ease of cranking two ways, first get a new sleeve , and buy a new ring from the guy who bought Frank Bowman's company, tell him you want one with a tight gap (Izero gap) the open the gap up to .001, break the engine in very slowly, running in a fat slloppy 4 stroke for 6 to 8 runs, the start slowly speeding the engine up, you will wind up with a motor you can hand start. the other way is to buy a ABC lapped piston/sleeve setup, they will have huge compression and a very good start.
regards
Randy
So, can I simply retrofit a ABC sleeve and piston for the current ringed piston and sleeve then?
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Thge wrist pin often degrades / corrodes , if anything has . So first check ! .
(http://resources.hobbystores.co.uk/product_images/large/X/X-IRV61-1135.jpg)
Pic of IRVINE ring , avaliable via. http://www.hobbystores.co.uk/default.asp?WPG=HOB_HomePage1&PageNumber=1&s=c:0,c:970,c:970-050,c:970-050-040 for a mere 7 pounds 75 p. :P
I found my ( one time ) supply fitted excellently to used pistons / took up the slack .
A NEW K&B piston & Irvine Ring , at first seemed stalled , but fit with zero vertical clearance but no binding , after a few cups of tea , :( .
SO the Irvine being a 20.000 plus late ( 80s on ) durable engine , its a ' off the shelf ' item that does the job . Well .
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Think if the abc case & the ring case are the same part No. the liners'd be interchangeable . But grab a new Gudgeon / Wrist Pin , whilst your at it .
Ive seen bronze bushed pistons , for the wrist pin . Assumed it Ex Factory , :-\ but seemed a bit unusual .
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Irvine 40 Rod FITS , ( & Gudgeon ) .
(http://resources.ripmax.com/product_images/combi/x/x-irv40-3145.jpg)
Throw in google pics , to find source .
Piston ( R E ) for comparison .
(http://resources.hobbystores.co.uk/product_images/large/X/X-IRV40R-1100.jpg)
Mine is a R E thrown together from a ' help yourself ' to obsolete parts stock of N.Z. Ex Importer .
Liner in it ( ringed ) is 130 Ex 110 Trans , for some reason . Only Ringed Liners they had .
their ABC set up is a differant C Case Bore , so none of those fitted the remaining S E or R E Cases .
C'Shafts the only remaining loose item I have .
A bloke here was donated the last new K&B 40 piston & spare Irvine Ring I had . a Speed Flyer , for a R I Torp 40 .
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So, can I simply retrofit a ABC sleeve and piston for the current ringed piston and sleeve then?
It can be retrofitted, but I do not know all of the parts needed, I have an ABC motor here, I would have to check out what parts you would need, of if just the P/S would work, I would FIRST , look at the Irvine ring , if it has a closer gap, it would be worth a try
randy
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The ABC sleeve has a bigger OD than the steel sleeve so the case would have to be bored out or buy a new case and head to make it a 4050 ABC. Besides the pistons are made from left over sportsman 46 pistons cut down and they are soft so lose the fit quickly.
MM
So both of the engines are bad quality ....and not worth the trouble it seems from what your saying ..... too bad
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in racing we found that a sharp flip backwards will give u one _ 2 flip starts comp or no comp
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Hi Bob:
What is backing to start all about? I find that this is the best method to use when starting my sport engines.
I read an article many years ago discussing why there is more compression when the engine is turned backwards but I forget the reason. Perhaps someone can chime in on this idea.
Be well,
Frank McCune
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Hi Bob:
What is backing to start all about? I find that this is the best method to use when starting my sport engines.
I read an article many years ago discussing why there is more compression when the engine is turned backwards but I forget the reason. Perhaps someone can chime in on this idea.
Be well,
Frank McCune
In ringed engines, they will have better compression in the direction the ring gap sits
If the gap is son the exhaust side it will have better compression flipping frontways
If ring gap is on the intake side it will have better compression flipping backwards
It should make no difference in lapped motors
Randy
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I thank everyone for the help on this. Having never owned a dykes ringed engine before, don't even think I had heard of them that I can recall (it would seem these came out during my long absence from flying) this was a new experience.
I've learned a lot in the last week. Just took it out to the stand again and it started instantly and ran good. My tach showed 11k rpm with a 10/6 prop while running just a touch rich. Carb worked good and transitions from full to idle and back well.
Think I have a decent engine at this point, and a project in mind to put it on.
Thanks to everyone!!
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In ringed engines, they will have better compression in the direction the ring gap sits
If the gap is son the exhaust side it will have better compression flipping frontways
If ring gap is on the intake side it will have better compression flipping backwards
It should make no difference in lapped motors
Randy
Additionally, for whatever reason, the gap on some engines wants to migrate to a particular orientation. All my ST46s (maybe 5-6 of them total over the years) had the ring migrate to the intake side and when not right, had lots of compression backwards but not much forward. Even if you assembled it one way, it moves until it is in the preferred direction.
One of the things I was going to try to make it more repeatable was get someone to put a pin in the groove, and I was going to file a notch in the ends to keep it in one orientation. In fact I was thinking about how to do it on my way to Golden State in 1988 - but when I got there, there was Paul Walker and the Impact/40VF. After that weekend, no one present thought they should keep trying to make ST46s work!
Brett
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(http://sceptreflight.net/Model%20Engine%20Tests/K&B%2040%20Series%2070F%20RC%20page%203.jpg)
justabouthesameas a ST 46 powerband . Timings about 140 - 120 so not far off . Tho the later front end is beffier , bigger passage .
Torpedos were in 29 , 35 & 40 , plus a .15 in a smaller case . They mustve made zillions 1960 - 2000 , a wisnewski injun .
(http://sceptreflight.net/Model%20Engine%20Tests/K&B%2029R%20Page%201.jpg)
cor : http://www.airplanesandrockets.com/motors/how-bill-wisniewski-reworks-his-engines-jun-1957-am.htm(http://[img]https://blog-001.west.edge.storage-yahoo.jp/res/blog-6d-af/hkclsp60kn7/folder/539706/70/2506070/img_0?1248950725)[/img](https://blog-001.west.edge.storage-yahoo.jp/res/blog-6d-af/hkclsp60kn7/folder/539706/70/2506070/img_0?1248950725)
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Additionally, for whatever reason, the gap on some engines wants to migrate to a particular orientation. All my ST46s (maybe 5-6 of them total over the years) had the ring migrate to the intake side and when not right, had lots of compression backwards but not much forward. Even if you assembled it one way, it moves until it is in the preferred direction.
One of the things I was going to try to make it more repeatable was get someone to put a pin in the groove, and I was going to file a notch in the ends to keep it in one orientation. In fact I was thinking about how to do it on my way to Golden State in 1988 - but when I got there, there was Paul Walker and the Impact/40VF. After that weekend, no one present thought they should keep trying to make ST46s work!
Brett
Most all of them did that, so did the ST 40 and 60 , several other engines would do the same, the rings moved, so I always pinned mine, I used a very small roll pin, it would stay with no problem, you could grind a notch into the inner 2 edges of the ring at the gap, I also sometimes just used a piece of piano wire, and peened the aluminum over the wire, both ways was OK, I drilled down thru the top, my friend Scott would micro drill the edge of the piston at the ring groove, you could use a piano wire piece and you did not even need to secure it, as the ring would keep it in place
I have ABC lapped stuff for my old 46 51 and 60s
Randy