Hi.

 I'm looking for drawings or just tips for the general dimensions of a Dykes type piston ring in model engine size. All the info I've found is for bigger engines. I've never seen such a ring live, so it's kind of difficult to start guessing the dimensions.
 Also, if I understand right, a Dykes ring needs less tension than a normal ring, how much would that be in comparison with a normal ring?
 The bore of my engine is 24mm (0,944").

 All help is appreciated!

 Lauri

I'd contact Frank Bowman, in the Vendors Forums. The Dykes ring for the Veco .61 should be .944" bore.

The ST G.51's don't have a Dykes ring. That reminds me, I need to send my G.51 piston and cylinder off to Frank.  Steve

I thought that AAC implied a lapped piston, and that a ringed piston implied a steel liner and cast ring, or visa-versa.  Are you considering a chromed aluminum Dykes ring, then?

The ST G.51's don't have a Dykes ring.

Thanks Steve, that was an oops on my part.

(Could have sworn they did though............)

 Hi.

 I'm looking for drawings or just tips for the general dimensions of a Dykes type piston ring in model engine size. All the info I've found is for bigger engines. I've never seen such a ring live, so it's kind of difficult to start guessing the dimensions.
 Also, if I understand right, a Dykes ring needs less tension than a normal ring, how much would that be in comparison with a normal ring?
 The bore of my engine is 24mm (0,944").

 All help is appreciated!

 Lauri

Lauri

You would need to also make a Dykes ring piston, they are different than the one you are using now

Randy

 To be honest, I'm just curious about comparing differend ring types. To make them (and the new piston, Randy) is not a problem.
 The engine I use has about 700 flights on it and I'm still waiting for ring-related problems. There is absolutely no trace of carbon/castor buildup in piston/cylinder, even though I've tried hard, even with full-castor fuel. I think it's because of piston scavenging, good materials and the aluminium cylinder with integrated cooling fins.
 Actually, the low operating temperature makes the engine kind of sensitive to weather changes, it can be a pain in ass in cold weather. For this reason I'm working hard to make burning more efficient. At the moment the hotter air gets, the better it runs. L

 To be honest, I'm just curious about comparing differend ring types. To make them (and the new piston, Randy) is not a problem.
 The engine I use has about 700 flights on it and I'm still waiting for ring-related problems. There is absolutely no trace of carbon/castor buildup in piston/cylinder, even though I've tried hard, even with full-castor fuel. I think it's because of piston scavenging, good materials and the aluminium cylinder with integrated cooling fins.
 Actually, the low operating temperature makes the engine kind of sensitive to weather changes, it can be a pain in ass in cold weather. For this reason I'm working hard to make burning more efficient. At the moment the hotter air gets, the better it runs. L

Hi Lauri

I didn't think it would be a problem for you to make a new piston, I mentioned that because all that was being talked about is to try a new ring, The Dykes ring, of coarse is not compatible with your piston your using now, and I just wanted to make sure that was known. I may have a few new 61 sized Dykes rings, I will look.  The  "L"  shape of the Dykes ring is meant to take advantage of the compression ,and high pressure in the cylinder to enhance the outward motion of the ring, and seal better. I have made many dozens of all types and would suggest this if you want the best .
Make a new 2 ring standard type piston, make the rings thinner than the normal rings, this is meaning thinner in top to bottom thickness, My standard rings are 45 to 46 thou thick, my double rings are 35 to 39 thou thick, The thinner rings folllow the sleeve better, and you really need them to be thinner with double rings so you do not have a lot of extra friction, It also would help if you pinned at least the top ring either on the left side on a counterclock wise rotation. Or on the right side on the reverse rotation motors., this is looking from the front of the motor.
What is your bore?

Randy

 Thanks, Randy.

 The bore is 24mm (mic says 23,960mm for piston) As I said, at the moment we use a ST.60 ring, I don't think Robbie modified it anyhow before assembly. Ring thickness (height) is 0,98mm. The pin is in front of piston (rear exhaust), or actually a couple of millimeters to the left, so the ring gap is in the center. I think Rob only thought of symmetry when he was making the piston.
 What's the reason for your recommendation about the pin position?
 About the thickness, we've talked about going even thinner as you say, to about 0,6mm (23 thou). Remember the piston lubrification is very good because of the piston ports, and the bore is chromed. I allready got some Rossi .60 rings with that thickness but we haven't tried them yet.
 Please send a dykes ring if you find one. Even if it's not good size, it would be good to have an example.
 Some people have mentioned that Dykes would be more difficult to start. Should I worry about that?
 What is your opinion, which one is best for a stunt engine, a Dykes or a normal ring (or two)?

 Lauri
 

Hi Bill

Typically a Dykes ring is an L shape looking at it from the top to bottom, where a standard ring is just a rectangle or square.
Many, but not all Dykes ring pistons have a much smaller diameter at the side of the top of the piston, than the sides just below the ring.
This is because the ring is flush with the top of the piston, This way the pressure in the cylinder goes between the ring and the piston (top part of the "L" shape)
and forces the ring to expand into the sleeve.



Randy

Thanks Randy.

If I read your response correctly, other than proper groove for the ring, the rest of the piston can be whatever is needed/desired. Correct?

Bill

Thanks, Randy.

 The bore is 24mm (mic says 23,960mm for piston) As I said, at the moment we use a ST.60 ring, I don't think Robbie modified it anyhow before assembly. Ring thickness (height) is 0,98mm. The pin is in front of piston (rear exhaust), or actually a couple of millimeters to the left, so the ring gap is in the center. I think Rob only thought of symmetry when he was making the piston.
 What's the reason for your recommendation about the pin position?
 About the thickness, we've talked about going even thinner as you say, to about 0,6mm (23 thou). Remember the piston lubrification is very good because of the piston ports, and the bore is chromed. I allready got some Rossi .60 rings with that thickness but we haven't tried them yet.
 Please send a dykes ring if you find one. Even if it's not good size, it would be good to have an example.
 Some people have mentioned that Dykes would be more difficult to start. Should I worry about that?
 What is your opinion, which one is best for a stunt engine, a Dykes or a normal ring (or two)?

 Lauri
 

Hi Lauri

If you are using cast iron for the rings, I would never go thinner than 30 thou.  They are too brittle when made ultra thin. If you are using another material, you need to make sure it is very stable.
The answer to the other question is, rod angle ,When you pin the ring on the left side..when looking from the front, assuming a conventional rotation motor, you will get much better compression, which is greatly needed on starting, especially with a low tension Dykes ring. You get lower compression pinning on the right side, this is because of rod angle and the way pistons are pushed upwards from an angle, the crank pin is at the far right side on upstroke so it pushes the piston toward the left side of the motor, thus closing the gap, increasing the seal, the opposite happens when the gap is on the other side.
If using 2 rings set the top one toward the left side of the motor and the other 180 degrees apart.

Randy