MAX-OS 30-S Prop?

LAST EDITED ON May-20-04 AT 11:36 PM (CDT)
 
I just mounted a 30-S on a Lightning Streak. It has the stock strap on exaust with uniflow clunk tank. I'm using 10% nitro 29% castor. What is the prop size to use with this engine? I would guess start with a 9-6, but am unfamiliar with this engine.

I run a 10x5 with muffler pressure

Couldn't have said it better

10-5

Tom and Scott,

I have two .30RC's torn down now for cleaning. They were gummed up pretty bad. I have been unable to pull the liners out to check that the wrist pin is free. I have cooked them for about 3 days now. I have tried to extract the liner while it was hot, hoping that the difference in CTE's would be enough. No luck! Have you ever pulled the liner out of your engines? Any suggestions? What size venturi are you running? What is the diameter of your spraybar? One of mine has a head shim and the other doesn't. Any info on what a .30S has?

I have heard that these have pretty mild timing. Would they haul a Magician around ok? Do they vibrate much?

Any info appreciated!

LAST EDITED ON May-21-04 AT 03:51 AM (CDT)
 
Dave,

As I indicated this engine is new to me. I believe it to be stock and it has a .256 id and the stock NVA. I have 4 more of the .30's and 3 of the .35's. I am going to order the ST NVA's from Leonard here at SSW for the others. The od of the Stock NVA is .125. Fortunately all of mine appear to turn freely and have good compression. I don't want to tear 'em down until I at least try them. I thought I read somewhere the 35-S had the same timing as the Fox 35, I don’t know if the 30 is the same or not.

LAST EDITED ON May-21-04 AT 12:24 PM (CDT)
 
> ... I thought I read somewhere the 35-S had the same timing as the Fox 35, I
>don’t know if the 30 is the same or not.
>
I have had two OS Max-S 30's, and still have one, just haven't run it in a long time. I've never made a degree wheel or had an urge to use one of someone else's. I don't know how similar the OS 30 & 35 S's were. Mine did *not* run at all like the Max-S 35's. I never did get either one to run "on the break" for a 4-2-4. It wanted to run one way or the other, dead slow four cycle, and hardly fast enough for a loop, or straight two cycle.

Of course, it's entirely possible that even back in 1969 or so, when the Max-S's started being offered, OS didn't use a decent sized intake venturi on the 30's. Fox got by using the same intake size for both the Stunt 29 and Stunt 35 (quite large); the S engines were practically identical, it would seem, to Fox engines, so one would think that both would run in the same (Fox style) manner.

My own 30's seemed to work best for me in a "wet two", the way I would have set a GH Torp for sport and stunt. I did use 10-5's, or if I had some 10-6's with chipped tips from short clearance gear and/or a rough patch of pavement, I would trim those to 9 1/2" and balance 'em. The muffler thing hardly existed when the S motors were new; they are thus less well adapted to using such devices than newer engines. You may assume a loss of about 10% of the power compared to an unmuffled run, roughly the same as the old Fox experiences.

.

Kiwi

>Dave,
>
>As I indicated this engine is new to me. I believe it to be
>stock and it has a .256 id and the stock NVA. I have 4 more
>of the .30's and 3 of the .35's. I am going to order the ST
>NVA's from Leonard here at SSW for the others. The od of
>the Stock NVA is .125. Fortunately all of mine appear to
>turn freely and have good compression. I don't want to tear
>'em down until I at least try them. I thought I read
>somewhere the 35-S had the same timing as the Fox 35, I
>don’t know if the 30 is the same or not.
>
>Tom

The stock needle should be .155. The .125 needle was used on the OS 20 and 25 (plus some of the smaller displacement engines). And the venturi size, using a stock needle, should be larger that what you have. So, I am going to say, yours isn't stock.

With a stock needle of .155 diameter (or Super Tigre, also), try about a .272 venturi on the 30S.
With the FP (.135) needle, try about a .250 venturi.
With a .125 needle, well, take it out and use it on a Fox.

These numbers, by the way, are for the 30S, not the 35S. A little larger or smaller can be tried. But if you are way off, this may be why some are not getting the same type of runs with the 30S that they get with the 35S. The venturi should be different.

Thanks for all the help! I'm going to try this engine this weekend. I will let you know how I do.

Here's my suggestion. Get a piece of flat plastic or a piece of aluminum , which you can shove in the exhaust port (piston in down position). Put a prop on the engine. Now heat up the external cylinder case ( not liner) with a hot air gun (paint stripper, monocoat gun, a hairdryer, or if you are careful, a propane torch-soft touch!). After it feels hot to the touch, turn the prop, and hopefully the liner will lift up at an 1/8 inch or so (depends upon the thickness of the plastic piece). Hopefully now you can grab the lip and convince it to come the rest of the way! (you could also drop a spacer onto the piston, and redo the lift again.

Alan,

Tried that on both engines. No luck. Wasn't super aggressive since I assumed finding a replacement rod, etc. would be difficult. Strategy at the moment is to continue cooking the daylights out of the assembled engine in hopes that the wrist pin is freed up in both the rod and the piston.

Mebbe this weekend I can make up a rubber expansion plug-type puller to apply some direct force....

>Alan,
>
>Tried that on both engines. No luck. Wasn't super aggressive
>since I assumed finding a replacement rod, etc. would be
>difficult. Strategy at the moment is to continue cooking the
>daylights out of the assembled engine in hopes that the
>wrist pin is freed up in both the rod and the piston.
>
>Mebbe this weekend I can make up a rubber expansion
>plug-type puller to apply some direct force....
>
>Dave
>LA_Flyer

I don't know if the .30S uses the same rod as the .35S. I recall GMA before he passed on once writing that he had a whole bunch of .30S piston/cylinder assemblies on hand from converting customer .30s into .35s. Nobody wanted the .30s it seems.

Jake

The con rods for the 30S and 35S are the same.

>I don't know if the .30S uses the same rod as the .35S. I
>recall GMA before he passed on once writing that he had a
>whole bunch of .30S piston/cylinder assemblies on hand from
>converting customer .30s into .35s. Nobody wanted the .30s
>it seems.
>
>Jake

Probably the difference is more of size. You have the same size case, the same weight with either engine. The 35, however, is almost 17% larger, and thus more powerful. It is also why OS doesn't make an LA 20. Most people wanted the 25.

LAST EDITED ON May-21-04 AT 07:49 PM (CDT)
 

HERE'S what I do. Take a tin coffee can. Fill half way with water. PUT IN FOUR drops, NOT TWO, NOT FIVE, FOUR. FOUR IS THE NUMBER. FIVE IS TOO MANY AND THREE IS NOT ENOUGH...oh sorry, of dish soap. Put engine in can with water and soap. Put can on top of one of the burners on the stove and turn on high. COME to a boil and make sure that you don't spill over. Turn on Mid-low and boil for at least 1/2 hour. After cooking take engine out HOT and try to remove sleeve I USE CHANNEL LOCKS.... BE CAREFULL TRUN SLEEVE 1/16" and the sleeve should come lose. BE CAREFULL. If you make a mark on the sleeve it's ok as long as it's on the side and not the top of the sleeve. A little of 280 grit will clean up any marks. I also have rubber jaw pliers they work. I do ALL of my old engines this way. SPARKERS NEXT.

Scott (has sharp pointy teeth) Riese

Finally, something in Stunt I have experience with!

I've been flying my OS .30 on a 10x5 TF wood prop. Seems very happy with it.

And this particular engine is one I bought used with a broken lug and gave it a new case. Removing liners is very easy to do if your wife is at the movies: Heat up the kitchen oven to 275 degrees - - let it stabilize and pop in the engine for 20 minutes. After you find your cotton gloves and a wood stick, as soon as the engine comes out of the oven, take said engine and push the liner up from the bottom with the stick, then grab the liner wearing gloves and pull it out the rest of the way. Assembly is the reverse.

These liners are sweated into their cases, and they get varnished up over time. Much easier to expand the aluminum case and take the liner out without stressing it up. Keeps it round. The aluminum case expands more than the steel liner with the heat, and it's dead-easy to disassemble.

To reassemble, I usually stick the liner in the freezer to cold-soak it, and, again waiting for the wife to go to a movie, heat up the oven and reverse the process. It's usually necessary to remove the liner before removing the piston/connecting rod, as the extra space allowed by the liner not being there makes assembling conrod to crankpin very easy.

Good luck with it, don't force anything, and no metal tools near the engine when disassembling it.

LAST EDITED ON May-21-04 AT 05:14 PM (CDT)
 
Hi Tom,
I picked up a 30S that was almost new, but a R/C carb. I used the venturi and NVA from an old 35S which was about wore out. Since you have a couple 35S, you might experiment with that set up.
I'm also using a 10-5 which was trimmed to 9 1/2. (it was a little chewed on the tips)
Bill <><

Bill,

The .35s have carbs. Acording to Leonard it looks like my 30 has a venturi/NVA from somthing smaller. I recently picked up about a dozen OS engines. I can make my own venturis but will be ordering the NVAs from Len. The only engines from the OS stable I had wer about 35 or so years old. I used a couple of .35s in Profile carrier years ago. I have no Idea of when these engines were made. I have some .40H, plain and BB, a couple of .35s, several .30s, .25s and a .20. I have been doing a lot of scratch building in the past several months and will be trying them all out. So much I want to do and so little time. The people here on SSW have been pretty helpful. Most of my questions have just been in ignorance as I haven't been active in modeling for the last 30 years or so. I'm between jobs now but expect to be back at work next week looks like less time for modeling. I discoverd somthing this past month though, when I retire in a couple of years my wife is gonna have to get a job. Not for the money, but just to get out of my face.

Tom,

Don't tell her yet....

LA_Flyer