[mattsz]

Hi guys-

What's the stock HP output of our 500 UCEs, engine and at the wheel?

[ace.cafe]

Several dyno charts have been posted here, and IIRC they were around 19-20 hp at the wheel.
I don't know of anyone who has tried to attach the dyno to the crankshaft on the UCE to get engine hp.

The factory hp claim of 27hp would obviously be a claim of engine hp, but the accuracy of that claim is unknown. It would indicate 7-8hp power transmission losses to the wheel.

[mattsz]

Actually, that's perfect, Ace, thanks!

I'm heading to a motorcycle meet this weekend at the Owls Head Transportation Museum here in Maine, and we talked about using my 2011 B5 in a side-by-side display with their 1922 RE; maybe do some start-up procedure comparisons.  I thought it might be nice to have some specs on hand for comparison...

Their bike:

http://owlshead.org/collections/detail/1922-royal-enfield



some specs: Engine air-cooled single-cylinder, two-stroke, bore 64 mm., stroke 70 mm., displacement 225 cc., power rating 2.25 hp.

[NorEaster]

Mattsz
Thanks for asking the question... it has been one I've had for a bit now

[SteveThackery]

some specs: Engine air-cooled single-cylinder, two-stroke, bore 64 mm., stroke 70 mm., displacement 225 cc., power rating 2.25 hp.

Actually, am I right in thinking that the "power rating" was calculated quite differently from how we do it now?  These days we measure "brake" horsepower, which is a proper measure of power.  I vaguely remember they would calculate the hp back then, for tax purposes, rather than measure it.  Wasn't it based on the bore and the number of cylinders?  Rather than the actual power of the engine?

[olhogrider]

Actually, am I right in thinking that the "power rating" was calculated quite differently from how we do it now?  These days we measure "brake" horsepower, which is a proper measure of power.  I vaguely remember they would calculate the hp back then, for tax purposes, rather than measure it.  Wasn't it based on the bore and the number of cylinders?  Rather than the actual power of the engine?

I think they actually hooked up two Clydesdales and a Quarter Horse then had a tug-of-war to get the 2.25 hp rating.

[ace.cafe]

I think they actually hooked up two Clydesdales and a Quarter Horse then had a tug-of-war to get the 2.25 hp rating.

The manufacturers almost always quote engine horsepower, not rear wheel horsepower. Owners that get on the dyno get rear wheel horsepower figures, and are sometimes disappointed that it is lower than the mfr quoted power.
There will always be some kind of power transmission losses between the engine crankshaft and the dyno roller under the rear wheel of the bike.

[barenekd]

I'm always disappointed when I see manufacturer's horsepower ratings. There are so many variables. I'll take a dyno reading any day. My Enfield had 18.7 hp with an EFI muffler on it. However, I suspect that the reading had he not literally plug the pipe up by shoving a 1/2" O2 probe down about a 3/4" tube. Probably robbed me of some HP.
But the bike was mostly always adequate on power. A few steep hills at 7 or 8 thousand feet could kinda slow it down!
I found that being a bit inventive, it was certainly useable on the freeway.
Bare

[Arizoni]

The real horsepower of the 1922 RE was probably known to the engineers in 1922 but the published horsepower of 2.25 was based just on the engine displacement for tax purposes. 
Note that the 2.25 horsepower is 10 percent of the 225cc displacement.

That makes as much sense as the way they calculated horsepower in Europe and the UK for the cars at that time.

They used a "RAC" rating which was based on the bore size and the number of cylinders.  Stroke had nothing to do with it so this system drove the designers to use really long stroke designs.
The RAC horsepower was equal to the bore (in inches) squared multiplied by the number of cylinders  divided by 2.5.  (Bore^2 X n)/2.5.  = RAC horsepower

This gave the supercharged 8 liter Bentley 6 a RAC horsepower of 45 while the OHC 4 valve/cyl. engine was actually cranking out 220 brake horsepower.

Our 500cc single using the 10 percent rule would have a horsepower of 5.0.

[dginfw]

The real horsepower of the 1922 RE was probably known to the engineers in 1922 but the published horsepower of 2.25 was based just on the engine displacement for tax purposes. 
Note that the 2.25 horsepower is 10 percent of the 225cc displacement.

That makes as much sense as the way they calculated horsepower in Europe and the UK for the cars at that time.

They used a "RAC" rating which was based on the bore size and the number of cylinders.  Stroke had nothing to do with it so this system drove the designers to use really long stroke designs.
The RAC horsepower was equal to the bore (in inches) squared multiplied by the number of cylinders  divided by 2.5.  (Bore^2 X n)/2.5.  = RAC horsepower

This gave the supercharged 8 liter Bentley 6 a RAC horsepower of 45 while the OHC 4 valve/cyl. engine was actually cranking out 220 brake horsepower.

Our 500cc single using the 10 percent rule would have a horsepower of 5.0.

For many years Rolls Royce and Bentley simply listed their horsepower as "adequate"

[gremlin]

I think they actually hooked up two Clydesdales and a Quarter Horse ...........

+1   

[Ducati Scotty]

For many years Rolls Royce and Bentley simply listed their horsepower as "adequate"

Well, it was. 

[gashousegorilla]

  The 85' Yamaha VMAX  and the truth meter.  Interesting read......


http://www.hotrod.com/thehistoryof/113_0603_dynojet_chassis_dyno/viewall.html

[dginfw]

That was a good read. I had no idea that the dynojet rolling road was that recent of a development. I guess I just assumed it had been around longer and that it was the product of a big company instead of a single visionary.

[gashousegorilla]

   Yeah, pretty amazing guy with a great Idea.