Why don't they use radial engines in cars?

[krispos42]

I was pondering this after listening to Bill Cosby's "Fat Albert's Car" stand-up bit. Basically it's about how Fat Albert put an airplane engine in his hot rod. Funny, but it got the juices flowing in the ol' noggin.

So I began thinking... with the advent of front-wheel-drive cars and the automakers having to shoehorn a bunch of shit under the hood... why not make an automotive water-cooled radial engine?




If you orientated the engine so was the same as the tires, you could have the engine just inside of a fender, like on the passenger's side of the engine bay. Put the tranny in the middle, and mount the accessories to the tranny on the driver's side of the engine bay. Run the output shaft of the engine through the transmission and to a pully on the driver's side and use a serpentine belt to run the A/C, power steering, etc.

Any idea why this never took off? Do radial engines have bad power-to-weight or power-to-displacement ratios? Do they have a low rev range?

[gmoney]

1. cool graphic, but I dunno...

Isn't this sort of similar to the old "Wankel Rotary" engine Mazdas used to have? Any reason why those never took off?

Apart from an entrenched mindset that realizes there's an entire infrastructure out there that supports the old way of doing it?

[krispos42]

4. Nah, it's still a 4-cycle cylinder engine

It just moves like a starfish doing a strip tease!


But automakers introduce new engines every few years, so if they were designing a new engine for their small-car line because of new technology and new efficiency and pollution standards, why not a radial?

[flvegan]

2. Isn't there only one gear, forward, in a radial engine?

And then it's just all throttle? Though then I'm sure one could somehow rig a transmission to that, I guess. No idea.

[krispos42]

6. Well, they'd have to to a transmission on it...

...for the gearing. 4 or 5 speeds, just like a conventional engine. Transmissions don't care much for what's making their input shaft spin.

I understand that radial engines used in airplanes (think B-17s) have fixed gearing to the propeller shaft, but that's just something I read on Wikipedia. :shrug:

[flvegan]

9. If it made enough torque, one gear would work.

The Tesla is a one speed. I think the size of the engine would need to be huge though.

[DS1]

10. standard engines don't reserve their rotation

There would be no difference in operation. The rotary would have a rev limit, and be hooked up to a transmission like any other device design to twist an axle.

[krispos42]

15. Radial engines probably have the same rev range as a regular engine

I can't imagine trying to crawl through traffic with my car in 5th gear. :scared:


Don't electric motors rev a lot higher than most gasoline engines anyway? I though the Tesla motor could spin at like 20,000 RPM or something like that.





I can't wait for mainstream electric cars!

[flvegan]

21. Tesla redline is 13 or 14k.

[krispos42]

22. Damn, that's fast

My Subie redlines at 6k. Even those high-revving Acura engines with the fancy-shmancy variable valve timing only get to about 8k.

[NoPasaran]

3. Just guessing here

But I think putting a radial engine in a car would result in a rather high profile under the hood.

[krispos42]

7. Hmmmm... maybe too tall?

Maybe they'd have to have it stick out the bottom of the engine bay too much? Maybe a driveshaft wouldn't have enough range of motion?


That's a good point!

[Mugu]

36. That was my first thought as well. n/t

[Oeditpus Rex]

5. Size, I'd think

I'm no engineer, but I'd think to get a decent power yield, a radial engine would need to be about three feet in diameter with the cylinder heads.

Also, I don't think radials create as much power as conventional blocks. I'm referencing old technology, but in WWII, aircraft radials required 18 cylinders to generate 2,000 horsepower (two 9-cylinder blocks) while V-blocks did it with 12.

[krispos42]

8. Rotec makes a 110-hp radial that's about 32" in diameter

That would power a compact car easily. Of course, that's with 7 cylinders and 2.8L displacement. But it's carburated, not fuel injected, and the compression ratio isn't anything special.

If we did the same multiport fuel injection, 4-valves-per-cylinder stuff we're seeing that standard in today's cars, I bet that would boost power significantly.

[KG]

11. radials are air cooled. other that the VW i can't think of another successful air cooled auto engine

[krispos42]

17. Well, yeah... but I don't see any reason you couldn't water-cool it.

:shrug:

[SacredCow]

32. The only other that comes to mind is the Corvair....

Though not commercially successful, it was a pretty good car. My family had one, and one day I hope to score one to restore.

[Jamastiene]

12. I think I understand why.

You know how if your tires aren't balanced, it's a really uncomfortable ride and you do not have good control of the car?

Well, an engine that kept that motion up (like in your picture, which also reminds me of the dancing I see some women do in rap videos :P ) might would throw the balance of the car off while it is going down the road.

[krispos42]

16. Whole lotta shakin' going on? :-)

This is what most 4-cylinder engines in a car look like. They have counterweights molded into the moving parts to smooth things out. And they mount the engines to the car with rubber to help absorb vibrations.

[MajorChode]

13. I've seen a few motorcycles with radial engines

[krispos42]

18. Sweet!

Needs a cowling, though... decreases air friction, increases cooling.



7 cylinders, sweet!

[dembotoz]

14. what about those early mazda engines

perhaps not a radial but a rotary.

[krispos42]

19. Those rotaries never took off.

Something with the interior seals not working very well.

[jobycom]

20. Those were rotary. Looked like this.

The fuel and air would be forced into the cylinder in the larger gap, then the cylinder would turn so that the air and fuel were compressed into the smallest gap, where the combustion would spin the wheel and expel the exhaust.

[krispos42]

23. Check out this animated gif

[jobycom]

24. There you go. Hard to describe in a still photo. nt

[Blue_Tires]

35. cool design

but as applied in the Mazda RX-8 it is light on torque and a gashog...

[1]

25. "piston engine goes boing, boing, boing, boing, boing. but the mazda goes huuummm..."

http://www.youtube.com/watch?v=oHzeGEHWMjo

[jobycom]

26. As I recall, it's because the drive shaft is too high.

The drive shaft is in the center of the engine, so a transmission would have to convert that motion downward then outward, and it loses it's advantage.

A radial engine has a better power-to-weight ratio, which is why they were more popular for airplanes, and are easier to cool because the cylinders are individual (also makes them lighter) and face the airflow (which is why yours has to be water cooled, since it is turned sideways). But in an airplane the motion is applied straight to the screw, and the engine is centered in the compartment with the screw coming straight out of the center of the engine. In a car that's not possible, so the transmission is less efficient than an inline system.

I'm not sure if your idea of putting the engine to the side takes care of that issue or not. :shrug:

A couple of those plugs would be a pain to change, too.

[The Velveteen Ocelot]

27. They're a maintenance nightmare -- at least the airplane ones are.

[krispos42]

28. How so?

I mean, I understand they seem to still be using older technology like carburators, but I would think that an automobile-orientated design would be as reliable as a V or H engine.

OTOH, the radial engines I have seen in use (specifically, a B-25) dripped oil like a sieve while in operation and shortly after they were turned off. I just though it was a consequence of a 70-year-old design, though. Maybe it's an inheirent problem with the layout?

[MajorChode]

29. Radial engines can be fuel injected

All the ones I've seen use quite a bit of oil, but I'm not sure if that is inherent to the design.

Someone did build a radial powered race car in 1935, but evidently it never did actually race:
http://jalopnik.com/383661/1935-monaco-trossi-is-16-cylinders-of-radial-engine-awesome

New radials are being manufactured in all sorts of sizes. A few brand new aircraft still use them.

[MajorChode]

30. Interestingly enough...

The reason why radials were so widely used for decades is because of their simplicity and reliability.

[HopeHoops]

31. It would only work well in a rear-wheel drive - think flywheel.

The reason it was so popular on planes is because it provided linear stability. If you mounted it sideways, you would have a gyroscopic resistance when turning.

[kentauros]

33. Here are some other more efficient designs:

StarRotor Engine
Revetec Cam-Drive Engine






:D

[Blue_Tires]

34. packaging, f/r weight balance?

durability?