Echo BME twin
 

I just purchased a few crankcases from BME that will be used to make small twin engines using Echo weedwhacker engines. The parts that I received from BME are a nice anodized blue and the machining is very good. I am starting to get together the parts that I need to make an engine, it looks like I will have to use the 21.2 pistons and cylinders since I haven't had any luck in finding the 23.6 engines, if anyone has the 23.6 cylinders and pistons I would be interested in making a purchase. I started this thread hoping that there would be some other RCU members starting the same project and we could share information.

RE: Echo BME twin
 

Huey-pilot, I am in Mobile and have a bunch of new 23.6cc short blocks. How many do you want? I thought about making a twin myself when I saw the post by BME. Not sure how I would do the crank to make it secure and strong and not warp from welding it. Do you have any pictures of the case?

Tim

RE: Echo BME twin
 

Thanks Tim, I sent you a PM

RE: Echo BME twin
 

Huey-pilot,

Keep us informed as you progress. I saw the post as well but decided the project was too complex for my current skill set.

RE: Echo BME twin
 

Tim is sending me two short blocks and the case is on its way from BME. I can't wait to get started on this project. Everyone that is putting one of these together needs to post progress reports and photos to this thread. Then we can help each other out.

RE: Echo BME twin
 

I wish some-one would post some photos of the crankcase and also a photo of what the crank is to look like when finished. If that was done this project would get off the ground a lot faster! Thanks Capt,n

RE: Echo BME twin
 

I'll try to put a pic of the crankcase up here later on. The crank part I haven't gotten to yet. Something about too many projects going on... ? [:o]

AV8TOR

RE: Echo BME twin
 

Hey Capt,n I have two cases comming from Keith. The crank is easy now that I talked to him. Cut one end of a crank off flush with the counter weight. Bore a hole into the counter wieght to accept the other cranks end. Cut another crank down so that you allow for and have a flush fit when pressing that nub into the bored hole in the crank. Line up the cranks so that you are opposed 180 degrees and both rods will be at TDC at the same time. The counter weights are ground flat so when you pair them up all you need to do is tack weld them together in a couple areas. I will figure some way to make a jig or some setup to indicate them in as close as possible. Keith indicated to me that if you were off a bit it will not make a difference. I may for safety sake drill the front journal area and pin it. Keith said there were some that would walk and get out of line when welded. My welder friend said he can do the tig welding no problem and keep heat to a minimum too. I may have to try this before I tear down my machines to move them to my new house and shop. We will see. I am trying to finish assembling my new Carden 35% Edge now before I move. A few more nights wiring and a little time with the spray gun and I will be set. Maybe!!

RE: Echo BME twin
 

These cases are setup for the Homelite pyramid reed system Problem is that all the parts are obsolete and not available from Homelite. I found a guy who has these parts in limited supply. There are 5 part numbers that make up one reed assembly, sans the petals. Boyeson has these or will make them. I have 3 assemblies for my 61cc twins and will be getting more for these smaller twins. I will be getting some as spare parts just in case as these things are on the bottom of the engine. Whever is interested in these parts let me know. The guy is digging up the parts and will be calling me back to let me know how many complete assemblies he can put together. There are some other reed assemblies that may work. Echo has some in current saws but they are 30 to 33cc. Don't know how they would work here. My guess is they will be fine. Other than that you may need to machine an adapter to mate to the case.

RE: Echo BME twin
 

Hey Tim,

Put me down for a reed set for the BME twin we're all working on as well!! Please let me know when I can get it and how much. E-mail me if that's easier/better. UPS tracking says the two Echo 23.6cc engines I got from you should be here tomorrow.

Thanks!
AV8TOR

RE: Echo BME twin
 

Sure will Av8tor. This guy is a one man band fir sales with a few parts pullers. He has my number and is supposed to get back to me with the available bumbers of compete assemblies.

RE: Echo BME twin
 

Ok, thanks guy!!

:D <- (Happy camper, uh, flyer...)

AV8TOR

RE: Echo BME twin
 

The Brison 6.4 twins used the same reed setup, and maybe the D&B and Fox twins too...One of those companies should know....:D
The original reeds were metal...The Brison used the metal reeds, I think D&B had some made from fiberglass...
Just worked on two different Brison 6.4s, both had the same reeds, SDC 80 carbs, but different crank designs...

RE: Echo BME twin
 

Her you go guys. Got the cases and other parts today. Look real nice. When the time comes I think I can shave a little weight off the top of the case. We shall see. I would like to remove the anodizing too. I may try the bead blast cabinet and see what it brings me as I prefer the plain aluminum look. Otherwise these things are outstanding. Thanks to Keith for making them available to us. Will try to post the weight later.

RE: Echo BME twin
 

Tim,

I just ordered a couple of crankcases from BME as well. I'm going gas / glow on mine.
Please keep us updated on the crank splicing technique. I think this part is going to be outside of my current skill set.

Thanks

RE: Echo BME twin
 

tim220225: I do not see a split line. Does the crank install from the rear? Is the bushing for endplay? Thanks Capt,n

RE: Echo BME twin
 

There is a split line, very well hidden with the fine CNC machining.Where the BME logo is there is a prop outline and the split cuts right through the center of the prop. The crank works the same as anything else for installation. Exception being the rear bearing presses in from the inside like always but no seal is needed as the crank stub for the clutch gets cut shorter. The other unanodized piece goes over a third bearing that installs on the crank after the crank is installed. Slide the bearing on then the piece of aluminum and drill and tap the three holes to hold the bearing block in place. The milled slot is for the timing sensor to glue to. Now I wish I could come up with one or two cases like these for the 61cc twins I have here.

RE: Echo BME twin
 

Well I just weighed the case and it comes in at 11.7 ounces. The reed assembly weighs .7 ounces less gaskets. Here are two pictures showing the 3 pieces that make up the reed assembly, and another showing it assembled. The black spacer could be machined if need be.

RE: Echo BME twin
 

tim220225: Is there a option on joining crank parts? Instead of welding, could we send parts to a machine shop and have the crank broched for a spline and use a short press fit spline joint? It probably is a long shot. Can you get a photo of a crank made for this engine? Thanks Capt,n

RE: Echo BME twin
 

There really isn't that much material there once you cut the shaft and bore the hole. Once you chuck the crank and indicate it in you should have a pretty rigid setup. I would chuck the hub end and cut off the clutch side. Plenty to grip to there on the hub end. Center drill the crank and go. Your hole will be rather shallow as I can see it. I looked at a crank I had here for reference. Before I did any of this I would rework the hub end to rid the crank of the LH threads. Don't know of any crank pictures out there yet. I think Huey-pilot will be closer than anyone. Wouldn't it be great if we all lived close by and could see things first hand? Here is a picture of two cranks I sent to Av8tor a while back. Maybe these being next to each other will help. Visuals always do for me. I think both you and foamcut can do it, just dig in.

RE: Echo BME twin
 

I found what appears to be the correct reed assembleys. He has 6 left on Ebay. Item #140005316892.

Mark

RE: Echo BME twin
 

Will the crank look simular to this one in photo? Capt,n

RE: Echo BME twin
 

Capt,n it will look somewhat similar. Ours will have four counterweights and no steel bar between them. That engine appears to me as though it would run kind of rough and be unbalanced. The counterweights on ours will be 180 degrees opposed. Look back at my crank picture and you will see what I mean. The crank on the left will have the clutch end cut flush and faced to the journal then bored. I plan on boring a flat bottom hole. I suppose you could bore through too. Wouldn't make a difference and be a little easier to do. The other crank will have one end cut off and faced to the depth of the hole. They should fit together nicely as the journals are ground flat. Align them and tack weld them together. Most of the stress will be on the front half or prop side of the completed crank so I assume that is the reason for the external third bearing.

RE: Echo BME twin
 

What holds the piston pins in place on these cranks. Is it a press fit? Capt,n

RE: Echo BME twin
 

There is a pin that the rod and bearing ride on. Kind of like on a car engine crank. The pin in this case would be the journal of the car engine crank. The design on these little engines is very much like that of a Harley flywheel assembly. The pin is pressed in.

RE: Echo BME twin
 

I talked to Keith at BME a few days ago and asked what he thought about tig welding the pin on the front crankshaft, he said that it would be a good idea since the pressed in pin on the front crankshaft has a tendency to loosen.

RE: Echo BME twin
 

If you have counter weight 180 degrees of each other then neither one serves any purpose except to add weight and cancel each other out. Your building a boxer engine from what I deduce. If that's the case then the opposing reciprocating mass cancels each other out. Get rid of all the counter weight and put a straigt bar in the center as earlier pictured.
No offense intended but I think you have a little home work to do.
As I said, no offense intended. Nothing wrong with trying. But on the other hand this is a good place to get that kind of info!!!
Besides, trying is half the fun for people who like doing these kind of things. Don't give up and keep at it.
We all started at the beging at one time.
But then I could be wrong. I have read several times in the past things on this site that were wrong. 30 years as a mechanic taught me a few things.

RE: Echo BME twin
 

I was wondering about that myself.
Why would you need all that rotating mass?

Two rods on the same journal seems logical to me.
Rebalanceing, you should be able to get rid of most of the weight
of the counter balances.

But you will need someone smarted than me to figure this one out.

RE: Echo BME twin
 

You may be correct, however the case was designed and is dimensioned to be done the way we are trying to do it. Also there would be more machining and alignment issues than most here have equipment for. What would one do for example with the pin or journal of each rod? You would be removing a counter weight and then you would have to try to reattach the pin to the afore mentioned bar. I have done an Echo twin and that crank has a disc the size of the counter weights that is machined with two holes in it that the rod journal or pin is pressed into. Essentially the two counter weights welded together in the design of this engine is the disc in the true twins crank. In my mind this design is so simple and straight forward I would have a hard time altering it. More work and many more issues. Just the counterview. :)

RE: Echo BME twin
 

Are you going to set it up so one cylinder will fire then the other or will they fire at the same time?

If they fire at the same time you are better off with a large single cylinder.
Larger bore means bigger ports that equals more power.

The advantage of twins is they run smoother and sound really cool.

RE: Echo BME twin
 

Both pistons move the same way at the same time. The ignition only has one sensor and magnet so both plugs fire at the same time. Just like a Harley engine does. Twins are somewhat inefficient compared to singles but they are smoother.

RE: Echo BME twin
 

Two rods on the same journal would not work in a boxer design. The Harley rod design is knife and fork and is set in a "V".

RE: Echo BME twin
 

Here is the way I see it. Both pistons move outwards at the same time and reach top dead center at same time. This makes for better balance and is the only way you are going to get a pumping action to pull in air and gas. If both pistons went the same direction on one throw there would be no vacume to pull air & gas into crankcase. The air would be just shifting from side to side. Also the balance would be way off with 2 pistons stopping to left side of engine then back to right side. I say both pistons have to travel out-wards to top dead center...but maybe a better way to join the 2 cranks may be had. Capt,n.... Edit added Photo.

RE: Echo BME twin
 

Wow capt,n that picture sure is shiney and pretty. Someone spent a lot of time on that Echo 61cc crank and cylinders.

RE: Echo BME twin
 

I had forgot about the "Sucking Action".

You are absolutely right you would need independent crankcases to
have the fireing other than at the same time.

Each counter balance would have to weigh as much as the piston, rod and rod pin
to balance.

It's amazing how things fall apart when you forget one simple detail.

RE: Echo BME twin
 

Tim220225: That photo is right of the Echo website....nice for sure! That was part of the promotion of a twin chainsaw. Capt,n

RE: Echo BME twin
 

Been all over that site I thought. Can you post a link? They polished the thing for display I guess.

RE: Echo BME twin
 

I got my block today and should have the donor motors by Wed. Tim, did Keith give you a number for the third bearing? Also do the other two come from the donors or do I need to get something ordered up? Looking at this little block I may be inspired to build a 100. It would be a bit of work to whittle out a block manually but it could be done. I need to look around for some suitable donor engines. Are there any current 50cc reed valve industrial engines?

Mark

RE: Echo BME twin
 

Mark most everything from the short blocks transfer to the new case. The bearings in the short blocks are number 6201, pretty common. They are open or not shielded or sealed as there is a seal that presses into the case from the outside of the engine. In the new case you only need the seal at the front of the engine as the rear bearing is pressed in flush with the case. The case isn't machined through in the rear bearing support so you need to cut the crank off a barely proud of the outside of the rear bearing. May need to test fit the crank back there to make sure it doesn't rub the inside of the case. The front support should take the same size bearing. I will be useing a shielded bearing there. Shielded meaning there will be a metal shield on both sides of the bearing. I think this would be better than the rubber seal. Besides I don't think there will be room for a rubber seal anyway. I get my bearings from the local bearing hous Motion Industries. Any supply house can get these bearings. Tell them you want a 6201 bearing but the shielded version and they will fix you up. Don't know what 50cc reed engines there are out there but Echo makes several 30 to 33cc reed units. Also don't know that it has to be a reed engines to make one work. The Echo CS-346 is a reed engine with a standard piston. No window etc. The engines you will have are the same way. Also I don't think the other RC manufacturers are using special pistons in their engines. Most are Echo, Stihl, Husky, etc. cylinders and they were not reed engines originally. My Echo 61cc twin has regular pistons too. Also if you are open to other CC sizes you may be at something over 100cc. Making a case would take some time without CNC equipment but would be rewarding. You could make the crank the same way. May be a little heavier than some but not that bad. BME has used stock Echo cylinders and pistons for years. His cranks were and or are custom made though. Nice work can be done with a manual machine, a rotary table, and an indexer. I have seen a Volstro head for a Bridgeport machine like mine do incredible work. CNC put them out of business. For a home shop guy though they can be the ticket for CNC type work. I would get one in a heartbeat if I could find one. Well I have found them but the money is stupid. One will turn up though. Patience.

RE: Echo BME twin
 

The I.D. of the bolt on piece is only slightly larger than the area that the seal is supposed to go in. The only type of bearing that looks like it will go on there is a roller bearing. Is there a small o.d bearing in the donors? I will have to wait till they get here and check it out.