Formula 1 RC 1/3 with V8 engine

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bernimodels

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Hello Gents, I haven´t posted much on the forum before, but I decided it is time to show some of my projects.
I have successfully made some RC F1 cars in the past and some working 4 stroke engines, ( see here www.bernimodels.com). At the moment I am working on a F1 RC 1/3 scale car. It is a massive project as I have the determination to make all the systems that the real car has. The biggest challenge is the V8 engine, no doubt, but I also intend to make the gearbox, clutch and drive line, etc. This is why I think it might be interesting to show this project on the HMEM forum as I expect to learn a lot from your comments, and hopefully inspire others.
The complete car will also feature suspensions, tyres, steering, and control system, so you can actually have a real driving experience. I expect to complete it in a few years time.

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Welcome. thats some pretty serious modeling. Wonderful work.
Dick
 
I have got an Optimus BF20 L vario with CNC kit and rotary table. I am still a long way behind with CNC machining, but I have been learning a lot with the recent engines. Also a manual lathe.
 
I stumbled upon your site a couple months ago. Your work is impressive. My question is have you looked at what's been done in model engines? OS produced the FS-40S-C (6.5cc) with bore 21.2 and stroke 18.4. This engine was rated for peak power at 17kRPM and redlined at 21kRPM with normal construction (no different than the first aircraft version one they produced in 1982). Your bore stroke ratio will of course lead to a shorter engine overall, but I wonder how such a short piston will work at model scale. The RC engines I've seen with short pistons I would not buy, but they aren't popular so I don't know if what I saw was really a problem. Detailed information about F1 engines is not easy to find, so this is a unique project for sure. Gas or wire springs?

Welcome!

Greg
 
Hi Dieselpilot, I am glad you saw my website already.

There are many RC engines at this range of stroke, but as you say not with this level of bore/stroke ratio. I went for this construction as a) it is aimed to high revs (above 10000 rpm) b) I want to create the 1/3 scale of the real engine. The real engines have around bore = 100mm and stroke = 40mm ( so a ratio of 2-2,5). On my engine I went a bit conservative with a bore 35 and stroke 20mm.

With regards to piston skirt area and height it is quite aggressive for a scaled engine piston, but again I wanted to scale the real piston and it is not an engine aimed at lasting very long anyway. With this sort of construction there are less friction loses so therefore there should be a performance advantage.

And this is just a single cylinder test engine before getting on the V8. Any problems with cylinder design should pop up now and hopefully make my life a little bit more easier on the V8.
 
Sure, that makes sense. I look forward to hearing about how the short piston runs. That head looks great by the way.
 
This is a very nice project, with the large piston and short stroke and rod it will generate fast piston speeds at tdc, which will lend it's self to very good scavenging, I will be watching for sure.
 
Hi there! I have virtually completed the lower assembly of the engine. The crankshaft is finished and finally assembled with con rod inside the crankcase.

You can see that the crankshaft has 6 holes on the counterweight area. These will be filled with tungsten bars. This is to adjust the amount of weight on the counterweight as well as keeping the inertia low. On the V8 one I might not do it as it is a lot of hassle as the tungsten is really hard to work with. I have to use a right angle grinder and because the pieces are so tiny it is quite a dangerous job.

The bolts to on the con rod are M2. I will replace the current stainless steel by 12.9 steel ones.

The cylinder liner is from a Lapped internal H7 steel off the self tube, that I turned to fit the aluminium engine block. It is not hardened but I hope it will be just fine for this test engine.

I am going to use gasket sealant, like Loctite 5800 as I do not plan to use any joints on between the crankcase and engine block. Any suggestions?

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Nice work on the engine. Very unique looking

As for sealant. I would recommend a product called threebond. If you cant find it where your from go to a honda dealership and ask for Hondabond. Same thing but more money.

These sealants are designed for sealing flanges on engines, and would be ideal on your engine
 
I would use ultra grey silicone to seal the cases, this is what I use for my engine cases on my drag bike, you need only a light skim to seal them
 
Thanks guys, I think any of them will do. I will check what is easier to get.
 
three bond is the same product as ultra grey, the ultra grey is made by permatex either one works great
 
one thing that happens with small scale is th rev range increases. Galileo was the first to notice the cube square law as it applied to animals but it applies to mechanical engineering. with 1/3 scale you may be increasing the rev range 3 times. your port area to cylinder volume ratios should allow for this if the ports have the same efficiency as full scale.

bore to stroke ratio isn't as important as you think. the same displacement with the same BMEP makes the same power and torque regardless of ratio. a longer stroke makes for more mechanical advantage but a small piston makes for less force. it balances mathematically. one doesn't have an advantage over the other. the reasons long stroke engines make good torques have to do with other factors. a small bore will shroud valves of the same size, so valves are either smaller or flow less effectively. the results are more air velocity to create charge motion. the other thing is the rod/stroke ratio is often decreased with a long stroke giving more velocity at the top of the bore and less at the bottom, this may give the intake charge more energy as well but also gives the piston more mechanical advantage at the top of the bore, this may be beneficial when the burn rate is very fast or the engine is running slower..


formula 1 engines have a short rod so they have a low rod/stroke ratio despite the short stroke. the biggest reason this scale engine might have trouble is the valve area may be just too large to generate velocity. it may have difficulty idling. the idle speed can be several thousand rpm. you can bring the rpm range down with a really short intake came lobe timing that is retarded to give a late intake valve opening. simply retarding the cam could increase the rpm range by giving a late closing which works at high rpm because the port motion will lag behind the piston, but if you only have a late opening the piston can generate some suction before the valve opens helping to ram the air into the cylinder. shorter timing will increase he average velocity.
 
Dman, I have to disagree with you about bore to stroke ratios not mattering, it all depends on the engine application, a nitro engine likes a long stroke to take advantage of the slow long burn rates, not so much a gas engine. I also believe the reason for short rod lengths in F1 is to shorten the dwell time at TDC and BDC to increase VE in an NA engine, I do think that the idle speed will have to be high depending on the port and valve size, the larger the port the higher the air speed is needed. prostock motorcycles found that when they went to the large port Vortex heads, the engines had to leave at 10000 to make any power on the launch.
 
Dman, I have to disagree with you about bore to stroke ratios not mattering, it all depends on the engine application, a nitro engine likes a long stroke to take advantage of the slow long burn rates, not so much a gas engine. I also believe the reason for short rod lengths in F1 is to shorten the dwell time at TDC and BDC to increase VE in an NA engine, I do think that the idle speed will have to be high depending on the port and valve size, the larger the port the higher the air speed is needed. prostock motorcycles found that when they went to the large port Vortex heads, the engines had to leave at 10000 to make any power on the launch.

if you map volume over time or volume to crank angle the only difference is rod:stroke. bore:stroke has zero effect on expansion volume vs crank angle. it's also note worthy that the difference rod:stroke makes is surprisingly small. 1.5:1 is very similar to 1.75:1 but when you push the extremes you can see a difference between 1.45:1 and 2:1.

long stroke engines may have more charge motion (tumble/swirl) for a combination of reasons and they have a lower cross section to displacement ratio giving them more port velocity. but the traditional explanations about "why" they have more torque do not apply. a scaled down engine has more cross section compared to volume, bassically a scale engine has less volume to take advantage of the port so the rpms will have to be higher. on a 1/3rd scale engine the ports will need to be shrunk down to .577 of the scale diameter to run in the same rpm range as the full size engine. i would expect this model engine to rev to 40,000+rpm.
 
The proof is in the pudding, this is a scaled down 4 stroke, not a two stroke it's not likely that the engine can flow enough air to reach 40000 rpms, and rod length makes a huge difference in charging formulas not included, for formulas are not the real world. I have built enough race engines to know. 😁
 
The proof is in the pudding, this is a scaled down 4 stroke, not a two stroke it's not likely that the engine can flow enough air to reach 40000 rpms, and rod length makes a huge difference in charging formulas not included, for formulas are not the real world. I have built enough race engines to know. 😁

it's a scaled down engine that revs to 20,000 rpm in full size. the ports are gigantic. the biggest thing holdings it back will be valve stability and and timing events. put some ducati style desmodramics on that thing as and see how fast it turns...

about the rod:stroke ratio, when it comes to this sort of thing sometimes a small difference makes all the difference. but reher morrison published a book and their opinion was that it's not worth worrying about. you build the engine to have a stable piston and good ring seal you you put the longest rod in it that doesn't interfere with the rings too much to keep the skirt short and that's all you worry about. i had a formula to map the curves on a graphing calculator and i showed it to a friend, he showed me the page in the reher morison book and that did the same as my formula and in print you couldn't see a difference between 3 overlapped curves. on my iphone screen with zoom you could see that there was a difference but the differences weren't visable to the full curve unless you put some very low numbers in there or numbers above 2:1. the difference to a pure sine wave was obvious but in the normal range of numbers used in performance engines they were similar.... i asked a long time racer about it and he said a stock chevy 350 was "about right" when he put long rods in they were heavy and didn't run worth a damn, and when he tried extra short rods he pushed pistons through cylinder walls. this sis something that is always going to be debated. all i can do is say what i've demonstrated mathematically and who has said what. other than that the discussion may never end...
 
Are you certain about rod stroke ratios of F1 engines? http://www.epi-eng.com/piston_engine_technology/comparison_of_cup_to_f1.htm

Besides, the goal here is recreating existing engine design not developing something new.

Greg

gues i was mistaken. i didn't realize the stroke would be that short... seems whenever i see a cutaway of these things the rod look short and leaned over pretty hard but perhaps what i've seen hasn't been accurate or i've seen engines from another open wheel series and assumed it was f1.. 2.5:1 certainly is not a "short" rod.. and what i am saying is that if you recreate an engine dimensionally you will end up with something that revs much higher both due to structure and airflow. galileo understood the idea that makes this true in 1638 when he notices big animals have thicker leg compared to their body size and that strength goes up with te square and weight goes up with the cube..
 

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