Jesse Open

I need to go back to work.Retirement isn't for sissies.

FlyerInOKC

My Feedback: (6)

Are you pass the point where you ask when you found the time to work for a living?

FlyerInOKC

My Feedback: (6)

Open rocker FA-30 for $100 anyone? It even has the chock assembly.

https://www.rcgroups.com/forums/show...ines-30-to-1-2

Hobbsy

My Feedback: (102)

Yes sir, I could use another 14 mm muffler for a 120 sized engine shoot me a PM for money talk, Thanks

Hobbsy

My Feedback: (102)

We may just have to accept a little binomial nomenclature where the prop driver is concerned. Fun eh.

Jesse Open

I always have recognized both terms. It wasn't I who questioned the correct use of "hub".
Not so with collet however.


No money needed, just send your address.

Glowgeek

You all may remember me receiving a low time 120 fathead. Tore it down and verified it was low time, very low time. The factory honing marks in the cylinder were like new, could barely see where the piston ring had run. The edge of the piston ring still has very sharply defined factory grinding ridges. This engine was obviously broke in and set aside for many years as it had a good deal of rust on the bearings and crank.

Anyway, I cleaned everything up, installed new bearings and set the timing and valve lash. All good UNTILL I tried to install the rear cover. As I tightened the screws the crank locked up hard. What the heck, I forgot the rear cover gasket? Nope. Hmmm, must not have seated the bearings properly, nope. Crud stuck between the pinion gear and crank shoulder? Nope. Crud between the spacer and pinion gear? Nope. Pissed off I gave up on it late last night.

This morning I removed the cylinder and decided to check for crank pin centering. Sure enough, the crank pin measured dead center of cylinder bore! What the deuce?!

Is it possible the rear cover is from a later engine? Anyway, my fix was to machine .008" off of the inside of the rear cover. All good now, engine runs spectacular.

FlyerInOKC

My Feedback: (6)

Good to hear you solved the problem! What are you plans for the Fathead, do you have a airplane in mind?

Glowgeek

The 120 Fathead is a perfect engine to use on 60 sized warbirds that need a morw weight up front to balance out. Hellcat, Bearcat, Corsairs etc. Also good for WWl bipes. Fresh out of any of those and it's not strong enough to fly my 60 size P-47 the way I want it to fly.

I just bought it for the experience. When I tire of it off to the marketplace it goes along with the a half a dozen of my other recently overhauled Saito engines.

Captcrunch44

had the same problem with 150.
there is definitely something different between I case and back plate and an other. Swapped out the back plate with the other engine and all was good.

Hobbsy

My Feedback: (102)

I had that back plate rubbing problem on one of the 120's, the rear bearings was about 1/64th" from being fully seated. It wouldn't pull in when tightening the prop, I had to finish pressing it and all was well.

Cap, your engines are on the way, tracking # by PM. Thanks

Jesse Open

Plus 1 on that.

Glowgeek

The crank will never pull the rear bearing in all the way if the front bearing is fully seated, it must be set fully with a press or with a drift punch. The front bearing controls the location of the crankshaft within the case ie the inner race of the front bearing is capured between the crank shoulder and the flange collet. (Did you see that Gary?). When everything is seated properly there is an intentional gap left between the crank counterweight and the rear bearing. The gap is there to accommodate thermal expansion of the case as the engine heats up. Kind of a scary thought but the inner race of the rear bearing actually slides rearward on the crank as engine temp rises!

Edited first sentence.

the Wasp

My Feedback: (1)

now with pride and assurance you can now change you user name to Fathead Saito LOL

Jim

Jesse Open

That 1/64" or .016" off seat that Dave mentioned is far more than any ends play that Saito may have designed in. Properly installed, both bearing outer races would be bottomed in their bores.And yes, I always heat the engine housing when installing bearing outer races.





A little side shot from 1979, USI Clearing Detroit Service Center Back in the heavy machine repair, sweat shop days. The iron link was heated with a ring burner for four hours. The two bronze half bushings were packed in dry ice at the same time. We lowered the bronze into the housing on tongs hung below the crane. Four or five men with maple blocks and 5 pound rawhide hammers would drive the bushings home together very evenly. You had one shot at it. Get it skewed and we were screwed.

FlyerInOKC

My Feedback: (6)

Impressive!

Hobbsy

My Feedback: (102)

Saito Buds, I received a heavy phone call from my daughter in W. Va. at 5:55 am, her youngest son died from a drug overdose. He was 25, I'll be gone for a few days. He is to be cremated with no kind of service. I'll go to support my daughter and her other four kids.

Captcrunch44

oh wow my thought’s and prayers go out to you and your family and especially your daughter.

Glowgeek

Oh no, so sorry to hear that Dave. Tragic at such a young age. Be safe out there my friend.

Jesse Open

Dave,

My heart goes out to the entire family, especially mom and dad. The loss of a child is a horrific experience.

Glowgeek

That bearing press is sweeet.

I have measured face to face of the bearing bores and face to face of the crank shoulders of several engines. Taking the delta of bearing thicknesses into consideration the clearance ranged from .006"-.009" on all except this almost brand spanking new Fathead, it measured .016". I measured and re-measured but that's what it is.

Either Saito designed it that way or there was a slip up in QA. As new as this engine is I seriously doubt the crank or rear cover was swapped out by someone but you never know.

Jesse Open

If I thought Saito designed that way, I would never own one. A minimal preload for this setup is quite acceptable. No room for .016" slop.

Thanks for the comment on the bearings press.

FlyerInOKC

My Feedback: (6)

Heart breaking Hobbsy! I wish you and your family all the best in this difficult time!

Mike

Glowgeek

Slop? No slop, unless you're using that term loosely to describe designed in clearances to offset cumulative tolerances.

There is no room for preload during cold assembly imo. I wouldn't want minimal preload cold and have side loads increase as the case expands. Saito didn't design it that way, neither did OS, Enya, YS or any of the clone manufacturers. The gap is intentional and necessary. Does it need to be .016"?, definitely not, .006"-.008" seems like plenty to allow for case expansion and machining tolerances.

Jesse Open

Care to educate me?
Slop would the outcome either way, be it bad geometric tolerances or shabby parts.
I am not inferring Saito intentionally made the slop, It is you who assumed they did.

Been doing this far too long to be baited into an argument with you. Worked with fitting and assembling. bearing setups from these toy engines to precision machine spindles to huge metalworking press bearings.
All good designs also specify the shaft and housing fit as well as the class of internal bearing clearances. Those clearances allow for the changes that take place when interference fitted on shafts and into housing bores.
Geometric Dimensioning and Tolerances is the actual, accepted practice. Properly applied, that .006" to .008" you prefer would be the final result, nothing outside that range.
All of that aside,back to the original thrust of my first comment;
In this application, a properly installed bearing should be seated with its outer race against the shoulder of the housing bore.




Go ahead, ignore that. Look for what you "want" .

Just like trying to explain the cam lobe position to you, I am done.