huey-pilot

My Feedback: (17)

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.

Eagle Flyer

My Feedback: (84)

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.

Ralphbf

My Feedback: (27)

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.

tim220225

My Feedback: (4)

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.

Ralphbf

My Feedback: (27)

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.

tim220225

My Feedback: (4)

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.

tim220225

My Feedback: (4)

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".

captinjohn

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.

tim220225

My Feedback: (4)

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

Ralphbf

My Feedback: (27)

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.

captinjohn

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

tim220225

My Feedback: (4)

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

airbornrc

My Feedback: (9)

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

tim220225

My Feedback: (4)

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.

airbornrc

My Feedback: (9)

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.

tim220225

My Feedback: (4)

Mark you just use the bearings and one seal from the short block. You need to buy the other bearing. Assemble the engine seal and all. Slip the new bought bearing on the crank then install the aluminum bearing carrier. Center punch, drill and tap the case. You are correct that all bearings are roller. The ones you get in the engine and the one shielded one you need to buy. A 6201ZZ has two metal shields and a 6201VV has two rubber seals. These should be less than $5.00. You could also use one with a single seal but I would be afraid of dirt working in.

airbornrc

My Feedback: (9)

I just got an e-mail back from Keith. The bearing that goes in the front is a 12mm x 24mm. A 6201 is 12x32. The one we will need is a 6901rs which is 12x24x6.

tim220225

My Feedback: (4)

Cool. Never thought to measure or try a bearing in the aluminum carrier. That number has a rubber seal on it. Glad I found out now so I can be prepared. FWIW I bead blasted the case and mount today to remove the blue annodize color. Came off like water. I will post a picture later tonight. I prefer the raw or milled aluminum look. Polished is good too but more work.

tim220225

My Feedback: (4)

OK guys here are some pictures of the case and mount all bead blasted. I am also listing the Homelite part numbers for the reed valve assembly that you need. These parts fit many of the Homelite saws. When you call they may ask for a model number, I used SXLAO for the model and UT-10045 for their internal number. The model number stands for Super XL with automatic oiler. Look back at my other post here for a picture of the assembly.

Part numbers are as follows:

59274- Gasket - Spacer
59718-Spacer
63260A- Retainer - Reed valve (the rubber seal that holds the reed petals to the pyramid)
63253- Seat - Reed valve (the pyramid that the reeds attach to)
59722- Gasket - Carburetor

Here are the Homelite obsolete parts dealers who have these parts. PDQ and Eversharp seem to be the easiest to get on the phone. There are more but you need to call Homelite parts line for more names.

PDQ 800-444-0732
Hawkins Brothers 573-588-4731
Charles Moody 315-845-8664
Eversharp 330-723-2480

The reeds in fiberglass can be bought from Boyesen Engineering 800-441-1177. The part number is OER30401. BME and Brison used the same reeds in their engines. The mount on these cases is designed for these also but of course you can adapt if you have something else. All the parts from Homelite come to about $22.00 or so. The reed petals are $6.00 each and you need four. Hope this helps everyone who has one of these. Took me a long time to find all this out when I did my Echo 61cc twin conversion.

captinjohn

Looks like using through bolts and carefull machining the case could look more streamlined and made lighter. Hard to tell though in only to photos! Capt,n

tim220225

My Feedback: (4)

You want to use the mounting plate. Not much meat when the plate comes off. I even looked at milling the logo off but I think it may get too thin up there. We will see, I need to measure the thickness sometime to make a final decision.

captinjohn

I think the mounting plate could be used and still use through bolts. Not sure Capt,n

tim220225

My Feedback: (4)

Do you mean running the bolts from the mounting plate in? The plate mounts with four bolts in the rear of the case half. No way to run them through. The cases are held together by two bolts each in front and back at opposing corners of the case. I looked at the case again, I may be able to shave just enough off to eliminate the logo. However at that point the washer behind the case bolts would stand above the case a bit it appears. Not a big deal but maybe not worth the effort. We will see.

airbornrc

My Feedback: (9)

Well My crank is ready for welding. It took a little over an hour to drill and tap the front shaft for a stud to get rid of the left hand threads, and cut off the rear crank and get it bored for the locating nub from the front crank. Most of that time was indicating things to make sure it wouldn't have any run out. The acual machine work only took a couple of minutes. I have an e-mail in to keith asking a couple of details on the welding and will share his answers.
While I am waiting for my welder to get to the crank I am going to make a mandrel to hold the cylinders and turn the fins down.
My case only came with two bolts that were too short holding the halves together. Tha case takes two different lengths of bolts, I ended up using two that are 30mm long and two that are 40mm long.

huey-pilot

My Feedback: (17)

Hi airbornrc, what thread size are you using for the stud in the crankshaft? Thanks in advance.