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OS FS26S-C 4-stroke development

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OS FS26S-C 4-stroke development

Old 05-16-2008, 05:47 AM
  #796  
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You can count me in for a kit Do you have any pics of the current setup?
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Old 05-16-2008, 10:39 PM
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Default PICTURES

Here's pictures of the very first kit to ever be "packaged" up. This is the one my "team" driver will be running next weekend. It's missing some stuff he already has on his truck from when he ran my engine last fall, but it's still cool to see all the parts together in one bundle.

I also attached some pictures of the completed truck. (minus the exhaust deflector - I had it off to take some measurements)
Attached Thumbnails OS FS26S-C 4-stroke development-img_3089.jpg   OS FS26S-C 4-stroke development-img_3090.jpg   OS FS26S-C 4-stroke development-img_3091.jpg  
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Old 05-20-2008, 07:09 AM
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Dp, what carb did you end up settling on for best performance? It just doesn't look like the AE one you spoke of earlier. I believe it looks like an O.S. in the pictures.

Could you explain how the front intake works on the head and how you've made them? I've tried about 3 different ways to make it work and have 3 leaky heads. There just isn't enough room there to make my original idea work. It looks as though you are using the standard pinch bolt. I'm at a stand still without a front intake head, the last part to complete my project AD2.

Very nice work though man, very impressive. Fourstrokes will be popping up all over the place when you get the kits ready.
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Old 05-20-2008, 08:29 AM
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Well, it took lots of thinking about how to properly seal and secure the side-intake manifold and also how to keep the port plug in place. In the end, it turned out to be a port plug, custom intake manifold, a couple 4-40 bolts, and 2 operations worth of machining on the head. I seal the port plug with Loctite 680 and Permatex Ultra Copper, and the intake manifold/carb with Ultra Copper.

My mill guy will be working on the heads next week. This week, he's making fan mounts.

The carb I'm using is the TZ-12 3 port rotary carb. It's smooth, very easy to tune, and almost as cheap as the Associated carb. If I had to guess what the highest performance carb would be, it would be either an old CV-R slide carb (works good on the FPM head), or the TM-18 rotary carb. It's a BIG bore rotary - which SHOULD work - though I've never tried one because they cost too much to include in the kits anyway. The kits and heads will come with a 10mm adapter so you can try both 13mm and 10mm carbs.
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Old 05-26-2008, 06:10 AM
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Looks great!Keep up the good work
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Old 06-06-2008, 03:05 PM
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Do the airplane version four strokes, introduce many more difficulties than the FS 26 VII marketed for the cars ?
I remember reading about the belt driven cooling fan, clutch system, straight intake manifold, two needle carburetors and also the straight and long exhaust pipes.
Does anyone know of another area of concern in using an RC airplane four stroke in an RC automobile ?

I would like to install a four stroke in a 1/8 scale RC car and I am thinking of the OS FS 40 or OS FS 56FS-a. I have begun thinking about the OFNA 1/8 Ultra GTP Dirt Oval Chassis because it has an optional two speed transmission and also aluminum clutch shoes.

Let me if anyone sees some obvious problems in my project.
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Old 06-06-2008, 03:23 PM
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Does anyone here know how to figure out speed, I have a CRT ofna truggy with a saito 91 4 stroke installed and running great. The spur is 62 and the pinion is 26 with a RPM of 13,000. I have the standard truggy tires. does someone know how to figure the speed. Have not ran it apart from on the starter box. It's been raining for over a week.thanks
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Old 06-06-2008, 06:08 PM
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Originally Posted by laro View Post
Does anyone here know how to figure out speed, I have a CRT ofna truggy with a saito 91 4 stroke installed and running great. The spur is 62 and the pinion is 26 with a RPM of 13,000. I have the standard truggy tires. does someone know how to figure the speed. Have not ran it apart from on the starter box. It's been raining for over a week.thanks
Well let me think. If the motor is turning 13,000 rpm, divide that by your gear ratio (62 divided by 26 = 2.38 so divide 13,000 by 2.38= 5462.2). Now divide this number by your transmission ratio. To get that count the number of teeth on the crown gear in the diff and divide that by the number of teeth on the pinion. This gives you the rpm of the tires. Now multiply that number by the circumference of your tires (you can use any unit of measurement but for simplicity let's use feet. You now have speed in feet per minute. Convert fpm to mph and you have your answer.
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Old 06-06-2008, 07:17 PM
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my crown is 43 and the pinion is 10 and tire Diameter is 5.59. help the math challenged. thanks
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Old 06-06-2008, 07:27 PM
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21.1mph.
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Old 06-07-2008, 08:38 AM
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thanks but I sure hope you're wrong, or I'll be needing a 52 tooth main pinion correct? to hit 42.2 mph
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Old 06-07-2008, 10:06 AM
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Or more rpm.
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Old 06-07-2008, 01:51 PM
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Here’s the pictures of my OFNA-CRT Truggy with a SAITO 91
Attached Thumbnails OS FS26S-C 4-stroke development-100_0970.jpg   OS FS26S-C 4-stroke development-100_0971.jpg   OS FS26S-C 4-stroke development-100_0972.jpg  
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Old 06-23-2008, 01:42 PM
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Default ELECTRIC FAN

I've been using an electric fan, just like on the picture.
Cooling was OK with a 2 cell ( not enough with one ).
BUT, far too weak. 1 or 2 jumps and all the blades of the
fan are broken. I did an alu ring around the housing to hold
tight the comlete fan. No way. Result 5 broken fans in
30 min run: EXPENSIVE.
I did on a truggy with OS FS40SC? a transmission with
an "o" ring belt and a kyosho fan.
Temp is perfect. Unfortunately the belt falls out A LOT.
The mounting of the motor and fan are quite rigid.
The pulleys comes from Kyosho and the belt is same size.
I manage to mount a tensionner on the return side of the belt.
( Not shown in the pictures )
No change at all.
Has anybody a solution to avoid the belt falling?

Congratulation to DP-buggyboy for the job he is doing.
I'm sure the 2 stroke engines will die soon due to pleasure and
torque given by 4 stroke.
Attached Thumbnails OS FS26S-C 4-stroke development-dcp_6170.jpg   OS FS26S-C 4-stroke development-dcp_6174.jpg  
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Old 06-23-2008, 02:12 PM
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Thanks. The 2 strokes aren't going anywhere - people will continue to like them for quite some time. Maybe if the manufacturers get into the game making crazy-high performance thumpers, our hobby will go the same way the motocross industry has - but that's many years out still.

I glue a nylon washer to the front of the fan pulley which keeps the belt from skipping off. It needs to be about 1/4" larger diameter than the pulley. This allows the belt to run loose (as it does with the stock belt) and flop all over the place without skipping off. Run it too tight (too small a belt) and it will break. You might need to do something similar to the drive pulley too. My drive pulley is captured by the flywheel and front engine bearing, so no skipping problems there.

I've had similar problems with other cooling fans of various types.... They're just too brittle and break easily - even if they move enough cooling air. I'm currently having a custom fan bid from a place that specializes in making plastic fans. It's the last thing that's holding me up and it's driving me absolutely CRAZY! It's okay though because I took it out on the gas truck last Saturday. Ran through 1000cc's of fuel, 2 receiver packs, and a few sets of tires. Yes, that's LOTS of laps!! After the initial tune, I didn't need to adjust the carb all day. That was what I was testing, and it went WELL.
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