AnthonyH

I see what your talking about now...that item (on Mcmater) is actually an linen based phenolic material...which is similar in mechanical strengths to the G10, but is not the same material. The G10-FR4 is an epoxy impregnated fiberglass material. The "Garolite LE" is a continuous cotton woven cloth impregnated with a Phenolic resin binder and is always much cheaper, but doesn't maintain the same chemical resistance and temperature ratings as the G10/FR4 material. The company I mentioned above doesn't sell sheets or blocks of the Garolite LE, but they appear to machine it : [link=http://www.jjorly.com/phenolic_machining_fabrication.htm]http://www.jjorly.com/phenolic_machining_fabrication.htm[/link]

Now I understand why it was so cheap....thanks for the clarification.[8D]

On page 3351 is listed the G10/FR4 type Garolite with prices. I've used it a lot in the past and it is G10 and not the red linen fibre or phenoly you mention that is on page 3350.

Enjoy,

Jim

Getting back on Topic;

Yes commercial engines do cost more. In my case, much, much more. I have a 34cc Briggs and Stratton Four stroke Gas engine. I converted it from a Sears weedeater. The wacker (used from Ebay) was 100.00 with shipping. I paid Wackerenngines 18.00 with shipping for a hub. A buddy of mine made the 1/4 inch back plate and my band saw took care of the rest. I have a great running, dependable, (and oh boy does it sound good) engine for 118.00. Fuji, the only commercially availible four stroke engine that I know of for RC, has a wopping 799.00 on thiers. This engine does include an Electronic Ignition, but for 189.00 I could have that to. Even with the extra cost of EI, I would still only have 307.00 into the motor. Now,a savings of 490.00 is somewhat profound.
I do however agree with a comment that was posted way up there someplace, the real difference is how you feel about doing the conversion yourself. Its a great fun to play with these suckers and end up with something "I" built. And of course you can brag to friends how cheap it was. I have a feeling it really isnt about saving money to most of those that look down on conversions, I have a feeling it is all about bragging about how much they paid. To each thier own. Just go out and have fun.

By the way, I have been told that P-Tex (those cheap cutting boards you see at the department store) makes a darn good material for carb spacers. Any comments? I havent made one yet, but I would like to make a smaller one for my four stroke gasser. What are the dangers of reducing the size of those things? Why are some so long? (to make it easier to get at?) Thanks for the help.

.

Ralph,
You have to quit doing that "edit" thing. We all know you had something to say, we just know what it is when you do that. Just let it go Ralph......


Prop Nut,

I think you are right about those who bad mouth conversions, not because of how they run or look, it's more about how much they didn't cost. And also the fact that the engines aren't really "airplane engines", therefore there must be something wrong with them....somewhere or at sometime.

Prop :

The PTEX ( AKA SRB) material is a UHMW (Ultra High Molecular Weight) based plastic, that is primarily used on skis and snow boards. The UHNW, as the name implies, is a very dense material such as the G10 and phenolic.

Never used it for Carb blocks but I will get a chunk and let you know. I see that the PTEX also comes with a graphite binder...how cool. Don't know why some blocks are longer than others, can't imagine it would improve performance...maybe longer is for a slide carb?

On the question of the cost of conversion of
a Ryobi 31 cc. For my part, I have done this conversion and I have a great
engine for less than $150.00 (less than half than comparable "model
airplane" gas engines). With that said, I just read a review of the Zenoah
G26 in an issue of Fly RC mag. Guess what? My weed cutter Ryobi
conversion turns a 16x10 prop at a higher RPM (8,100 vs. 7,260) and idles
lower (1,400 vs. 1,860) than the G26. And my tests are at 5,500 ft altitude
with 15% thinner altitude, which knocks the crap out of engine horsepower.

As for weight my Ryobi is almost 1/2 pound lighter (51.1 vs. 58.3 oz.). I
should add that I added a homebuilt electronic ignition and dumped the stock
one pound flywheel/coil assembly.

Granted my $150 total cost doesn't include some of my labor and my friends
machining (I owe him a lunch). I should add that I pulled the Ryobi out of a
new, reconditioned weed cutter from Harbor Freight. Cost $49.95.
Also my 31cc is 22% larger displacement that
the G26 @ 25.4cc which slants the comparrison in the direction of the Ryobi.

Therefore my observation is that the engine conversions are at least
comparable to other gas engines in their displacement class and cost less.
What's wrong with this logic?

Absolutely nothing!



AV8TOR

Other than itreally peepee's off the OEM guys. [:@] Also the people who need to feel good about spending BIG dollars for the motors in their planes!!

Let's see. My first conversion (I'm brand new in that 'business':

Engine: Poulan 25cc Weed eater head (new) $25 plus $10 S&H (no tax) from ebay.
Prop hub: 1 dollar worth piece of T6 rod Plus 20 cents for prop screw plus 5 cents prop nut.
Motor mount: 1 dollar worth of T6 plate plus 40 cents 4 screws.
Pleasure working with metal: priceless

Now I doubled the value of my engine by adding aluminum muffler from Wackerengines. Includng muffler and mount it weights 3lb 8 oz (8 oz more than MVVS that size with muffler, mount, ignition and battery for over 450 bucks). Even with magneto and stock carb the engine turns MA 16x8 7200 rpm (on 1:30 fuel) and idles 1800+ rpm. I was surprised with transition as it goes from idle to full without hesitation like any 'brand name' 3D engine.

Anyway this is the cheapes engine ever I bought (it's cheper than any glow engine) and entire conversion took me about a day.
Remember, I never did it before. The next one will be even easier.

RysiuM

RysiuM,

What are you putting that 25cc engine on? Or have you already flown it. Tell us about it.

You may have already seen that thread [link=http://www.rcuniverse.com/forum/m_3082557/tm.htm]Poulan 25 from FL trimmer[/link] where I described entire conversion.



The truth is, that first I had and idea to build 1/4 scale PZL1-9 Wilga 35/80, next I got plans from UK. Now when building the fuselage I had to stop at the firewall to make sure the engine will fit right. As it is not a high performance plane I thought that cheap weed whacker will do just fine. Actually it does much better than I expected.
I estimated the weight of this 1000 sq inch plane will be 13-15 lb including 4 lb engine, and because it has very short nose Poulan fits just fine. I had to scale original plans to 90% as I wanted to fit the fuselage in my truck with 6ft bed. So it is about 68 inch long and 98 inch wingspan.

Anyway the engine is finished now, ready to run so I'm going back to the plane. It is fun as original plans sucks and I use them mostly as a general view coming up with my own engineering solutions. I'm just so happy I could get away with 50 dollars power-plant (including new muffler).

RysiuM