Scale Furai - Scale 20B Nitro Engine
 

Hey guys, looking for some help on a project I have recently started. I have a lot of ideas right now for the engine on cooling, custom center plate, e-shaft, fuel system, etc. I have complete some solid models of what the engine should look like and now have to begin machining the parts.

I have been back and fourth on the car to build, but thats to Rotr8's advice I decided to go with my original plans and build a scale Mazda Furai. However, finding information on the car was next to impossible and the pictures I was working off were not the best to use for scale. I have been trying to find pictures of the Courage C65 carbon monoque and rear frame, but they are understandably hard to find. If anyone has any pictures and would not mind sharing them (I would keep them to myself if you request) I would greatly appreciate it.


If anyone has any advice or ideas I would really appreciate if you would post them!

http://i214.photobucket.com/albums/c...00/3515-12.jpg
http://i214.photobucket.com/albums/c...aFurai2008.jpg

Here are some engine pictures and more of what I have on the cars. They need some cleaning and maybe a rebuild (no side or oil seals, just apex), and maybe some new bearings. They are rated at around 1.2 hp each at up to 18,000 rpm...my version will probably not be able to spin that fast but we will see. The last two pictures are not mine, but shows what the rotor, seals, bearings look like.

Here is a video of a guy with two engines attached in a rc tractor. I'm looking to go more "traditional" and follow a 20b with sideplates and not jsut attaching two engine back to back. Got in touch with a guy who is sending me some CAD drawings and pictures from this tractor engine for ideas (he also has a bimmer with a 20b turbo!).

http://video.google.com/videoplay?do...s+wankel&vt=lf

First Part - Eccentric Shaft
http://i214.photobucket.com/albums/c...0/P1010056.jpg
https://www.rx8club.com/picture.php?...pictureid=5465
https://www.rx8club.com/picture.php?...pictureid=5463

save for pics...

https://www.rx8club.com/picture.php?...pictureid=6485
https://www.rx8club.com/picture.php?...pictureid=6484
https://www.rx8club.com/picture.php?...pictureid=7993
https://www.rx8club.com/picture.php?...pictureid=7994
https://www.rx8club.com/picture.php?...pictureid=7992
https://www.rx8club.com/picture.php?...pictureid=7991
https://www.rx8club.com/picture.php?...pictureid=7990

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sweet post Brent

thanks man, felt like I needed to get a little project going.

I don't know how much this will help you or if you've seen this model, but I thought it was relevant to your nifty project. I wish you the best of luck!

^Wow, that's pretty sweet, a liquid cooled single rotor setup. Me like!

I used to be into 1/10th and 1/8th scale on-road R/C nitro cars, and I wanted to do a custom two-rotor OS wankel engine build a while back, but then I got my 8 and sunk money into it.

This would be pretty sweet. Are you going to build the car to scale around the scale size of the OS Wankel engine? That would be awesome.

Please keep us updated man.

^ exactly what im going for. i should get the motors on monday or tues then ill be able to get some dimensions for scale. not as interested in top speed performance in this project as I am in making it look and function like the real thing.

I do not have much experience with nitro cars so im going to have to find someone to help with the tuning. from what I have read nitro wankel engines are a pain to tune.

The hard part is scaling the car from pictures alone. I have been able to use the wheelbase to get scale in pictures I found online so that helps out a lot.

Good luck with the build!

have you contacted racing beat? I believe they helped with the engine work for the furai

thanks!

thanks, Yeah I am going to drop them an email asking about the exhaust.

Did they do the intake as well, and do they have a user profile on here?

Wow, this sounds utterly awesome. I'm going to keep my eye on this!

got two of the engines in today, they had compression! the seals are in good condition, very light chatter, need a good cleaning tho. Also included one for perspective.

http://i214.photobucket.com/albums/c...0/P3160006.jpg
http://i214.photobucket.com/albums/c...0/P3160010.jpg

thanks cyber

don't expect too much too fast tho. Still in school so I have limited funds and time. Get access to a machine shop with water jet, cnc, welding, plus a few others...just have to convince them its for "school" projects.

Now that I have the engine I can make a solid model of the engine. Hopefully have a version of that done in a few days.

is it going to be turbocharged?

there are turbo kits for r/c cars you know.

This is really cool? How much do you think the final price of the engine will be? I would love to tackle something like this, a neat little toy

^ all depends on what you want to do. So far I have bought two used complete engines (OS 30 Wankel) for $170 each. They are around $350-400 new and you need 2 of them for a "13b" so far im up to ~$350 on the engine.

I have access to a water jet and milling machines for the center/side plates, if you don't its around $40 an hour to have it sent away. I have not looked into materials for the plates/shaft yet, but I do not expect that to be more than $100.



I'm not going this route but here is another option for joining engines...

aww look at the little baby rotors :lol2:

that's going to be sweet! I always wanted to get a nitro rc car with an rx8 body and turbo it

NOW that is cool!!!! Get some video and a sound clip if you can, I could imagine what a pint size rotary woulld sound like! What would the revolutions be on such a small motor,15,19,maybe 25k rpms give or take?

Hey Brent look at this,, ,half way down theres a flyer from SevenStocks RC Cup,,,
Theres a scaled RC Furai body there....
http://www.sevenstock.org/

Looks like you can only get by participating in the Furai cup challenge at SS11 but maybe you can get a hold of one through someone who is there...

Here is a CAD drawing of what the engine will look similar to.
http://i214.photobucket.com/albums/c...Project1-1.jpg

might drill a 'U' shaped channel in the center plate to use for water cooling because of the heat from each of the adjacent rotors.

The main drawback is my comp in too old/slow for me to put any type of animations of the engine together. Ill try to make one of a single rotor and housing.

Let me know what you think or any ideas you have.

Just in a hurry to show I have been busy.

also, right now its around 2.26lbs with iron side plates and chromoly eccentric shaft.

pretty cool man...
Im not sure if it will work but heres an idea, look into machining graphite rotor housings, Pro- Self lubrication, cons- possibly weak over time...

finally I got an update for the project. I have changed direction a bit and have decided to build a scale rx-8. it will be easier since I can just go to my car for measurement, and cheaper since I do not need to buy another rc engine.

I also just got the RX-8 book by Jack Yamaguchi which has excellent information and suspension layout diagrams (must have for any 8'ers).

Last week I went and got a 7x12 grizzly lathe (works great) and just finished my first part of the engine. Took me about a total of ~35 hours to make the jig (aluminum) and machine the eccentric shaft (4140 chromoly). Here it is, I just have to trim the shafts and drill the holes in the lobes. Need to go back to school for that because I do not have a rotary indexing table with a chuck. Now on to the center plate.

If anyone has an RX-8 design diagrams would you mind posting them or pm'ing them to me. Thanks.

not the best but I have an ancient digital camera.
http://i214.photobucket.com/albums/c...0/P1010055.jpg
http://i214.photobucket.com/albums/c...0/P1010054.jpg
just finished turning now to clean the surface
http://i214.photobucket.com/albums/c...0/P1010051.jpg

nice update!!!

in response to this question, i couldn't even imagine. the small single piston OS engines get up to 50k, and now this one's a rotary. Assuming an average car goes up to 6k and a normal rotary goes up to 9k, and assuming the single piston OS engine is average, this baby will get up to 75k rpm :) whoa!

The OS rotaries can't get anywhere near 50K rpms. They are capable of hitting 20K though and hit their peak power at 16K rpm. I have one! 75K. Dream on!!!

Ahhh...my bad. When I had an hpi nitro car, they told me that the engines are capable of 50k. by using math, i assumed the same ratios :) guess not :lol2:

50K? HAHAHA! THat must be right before the connecting rod goes through the side. :lol:

this is defintely a sweet project.

makes me want to do something like this, that would be pretty sweet to have my own r/c mini rx-8.

can't wait to hear more updates!

ok. you think that. it's probably correct for the engine i had at least. refer to this: http://www.rccartips.com/nitro-engines.htm .

EDIT: sorry for "ruining" the thread. good luck, however!

Brent Ive gotta check theis out in person,,, the next meet you come to make sure to bring this with you...

You should contact some of the large RC manufacturers and ask for some free parts! lol A cool little project like this can attract attention from different people and what not. Get that car in a RC mag

=O nice, really impressive work. please keep us posted good luck with the project

Let's see it. :squint:

I agree with this suggestion, to some extent. I think your work is exceptional and could get lots of attention from the general public.

What technique was used for joining these engines? Just an adapter "flywheel" like piece?

I am working on a similar project and I hadn't seen this thread....funny! Good luck on your project!

Best regards,

Chris

Don't forget that real cars are 4 stroke engines, R/c cars are mainly 2 stroke so they rev way more by comparison.

Chris

dam this is crazy!!!

I had already posted this as a joke some time ago, but here it is again: Mini wankel

here is my almost complete 13b. So far the only remaining tasks are to buy threaded rod for the long bolts, thread the eccentric shaft, bend the exhaust tubing, and order some new apex seal springs.

The engine does not have the water passages drilled yet because I am waiting to see if they are truly necessary for the model. I will run the engine while monitoring the temperature to decide. I have attached the front OS engine cover (bell housing location) to hopefully gain some cooling from the side mounted fins.

The side housings and eccentric shaft were also heated until they were glowing red and then oil quenched to help harden the surfaces and increase wear resistance. Note to self: do not grab the end of the pliers that were holding red hot metal with you bare hands!

Rear side housing ready to be cut to shape.
http://i214.photobucket.com/albums/c...0/P1010005.jpg

Just completed grinding the rear housing profile, the alignment rods need to be cut to length.
http://i214.photobucket.com/albums/c...0/P1010011.jpg

The engine completed to this point.
http://i214.photobucket.com/albums/c...0/P1010013.jpg
http://i214.photobucket.com/albums/c...0/P1010014.jpg

I hope to have a video of it running in the next few weeks. Somehow during the machining I managed to lose one of my fixed gears so I will have to order one of them as well, great waste of $40.

What type of rpms are you estimating to spin? That tiny of a motor I am assuming the rpms would be north of 15k ? Also on your motor why does the housing have fins or spines on it? Is this for cooling, strength, stress or just by design ?

Such a cool project, keep up the good work.:)

^thanks, I appreciate it.

A single OS engine is capable of 1.27hp @ 17k rpm's. I cannot give an exact answer on what my red line will be but, since I have increased the size of the engine the rpm's should be below 17k.

The fins on the housing are for cooling since it is made for rc planes it is air cooled from the propeller.

This project is to develop a prototype to test my machining and get experience with small scale rotaries. If this works I have already begun designs on a scale engine based exactly from the 13b (1/4 scale), and will include side and oil seals, water jacket, oil lubricated bearings, etc. This will not be made from any available engines, so all parts would be one off machined parts.

Coolest project in the forum.

Glad to see you are still working on this project and making progress! Can't wait to see the video of this little wonder engine running! If you ever get to the point of making a kit, let me know please!

Sorry I'm late. This thread is awesome!

im glad to see you got it up and put together.

get video of it running. very cool.

I was going to do this a while back as well, until I figured out how big I'd have to make the car :lol:

pretty sweet progress, can't wait to see it done. :)

I can't wait for a vid. This is the greatest project on the site that I've seen.

thanks everyone!...I just got new seal springs, fuel line and fuel tank in today. Hope to have a video soon.