Horsepower

I often get the question "how many horsepower (or KW) is your model" Is there someone who knows? Talking about the 4"agriculture now
Alex-Jan

Stil no replays. There should be a formula but I do'nt remember.

From the dim and distant past 17LE

IIRC at Dorset a few years ago a 4 1/2" or 4" Burrell was dyno tested and produced 1 1/2HP.

I remember reading how they worked out the horsepower for a traction engine which is totally different to the horsepower of a car. Basically you take the diameter of the cylinder and the stroke, multiply them together and divide by 10, then round it up or down. eg. an 8" diameter cylinder with an 8" stroke = 64 divide by 10 = 6.4 so the engine would be a 6hp engine. Applying that to our little engines with a 3 x 3.25 = 9.75 divide by 10 = 1hp. It gets a bit more complicated with a DCC.

Blimey Steve, that's a bit crude, dosn't even take into account "operating pressure" which has a BIG influence on power!!
Try this, full size equals say 6 horse power, 1/3 full size equals 2 horse power!!! (Ha Ha Ha!!)
Tony

Bear in mind this was only a guide to the power of the engine, we are so familiar with the power of this & the power of that being accurately measured now. 150 years ago the horse reigned supreme for most sources of power and as far as engines went they just wanted to know "would it do the job or not?"

I guess your right on that count. If one our little ol 4" agricultuaral engines can pull a 2 ton truck then I reackon that's power enough to do most jobs at that scale!!
Looks like "on average" the answer to the question is "around one & a half horses"!!!
Perhaps STW could give a definative answer............... Well Craig!!!..........
Regards
Tony

don't ask me

really not my area, Steve is your only hope from this direction

Well going out to a event for the next4 days, giving a answer to the public, asking how many.....
Regards Alex-Jan

I can't find the original article regarding horsepower but I have found an article in the Burrell Style book which relates solely to Burrells and effectively gives a similar result. I've reproduced it below:

The reference to engine size by means of nominal horse power rating had been used since the earliest days and for single cylinder engines was calculated on the diameter of the bore, the piston stroke not being taken into account. Virtually all makers followed the system using the formula NHP= DxD/10 where D is the cylinder diameter in inches. Thus the following standard dimensions were established and used to the last days:-
NHP Diameter Stroke
5 7" 10"
6 8" 10"
7 8.5" 12"
8 9" 12"
Steam pressure and piston speed were ignored but generally these factors were fairly consistant such that the variation in output between the different makers did not amount to very much. The exception was the use on the late Burrell engines of a working steam pressure of 200psi. which raised the power for a given rating above others.
The introduction of the compound system meant that a different formula was required and exactly what this was has never been established, makers generally following their own ideas on the subject. One assumption that could be made was that, since under ideal conditions equal work was done in high and low pressure sides, one half of the total NHP was to be derived from the high pressure cylinder thus.
1/2 NHP = DxD/10 where D is the diameter of the high pressure piston.
or NHP = DxD/5
The diameter chosen for the low pressure piston reflected the total number of expansions intended, bearing in mind the cut off in the high pressure and the desire for equal output from each cylinder under normal conditions of work. Usually the low pressure piston area was about 2.8 or 2.9 times that of the high pressure and calculating accordingly the hypothetical dimensions could become as follows:
NHP Dia HP Dia LP
5 5" 8.5"
6 5.5" 9.25"
7 6" 10"
8 6.25" 10.5"
10 7" 12"
Again the rating ignored stroke, speed and steam pressure but gave a guide to size with an actual output equal to or a little above that for a single engine.

So for the SC with a diameter of 2.75" 2.75x2.75/10 = 0.75 NHP

So for the DCC with a high pressure diameter of 2.28" 2.28x2.28/5 = 1.039 so a fraction over 1 NHP

So by these figures the DCC will have just over 33% more power than the single crank engine

I hope this has shed a litle light into a murky corner!

I've just seen that the spacings have all dissappeared from the figures! hopefully you can still make sense of it though.

Well done Steve, good lesson in old fashioned power equations, very interesting & informative.
Tony

An old thread but one I thought was worthy of bring up as I had the chance to Dyno my Agri at Hollycombe last weekend

Basically the set up was a LARGE motor/generator on a trolley with the a load of what I think was a couple of electrodes in a salt bath. A ammeter and volt meter were then used to get the wattage which was then transposed to HP.

The little Agri managed the grand total of 763 watts or there abouts, which equates to just over 1HP, another Agri managed about 1.25HP, I think I could have managed similar but the belt wasnt tight enough and was lashing about all over the place which I think was causing a bit of loss. I'd have liked another run but it was too late in the day really.

Must admit it was amazing how quick it used coal and water to maintain 120psi with a fully wide open regulator even during the short runs we did with it.

So there you go a definitive power output for a 13 and a bit year old single cylinder 4" Agri which hasn't had any special attention to its set up

A year on and I got on the dyno at Hollycombe again, different belt this time which wasnt flapping about and with a full head of steam managed 1.35HP this time, in comparison there was what could be classified a almost brand new STW 4" that was on its 10th or so steaming which pulled 1.6HP, so again I'm very pleased with its performance given that its the 1st one from Batch 1, although some folks say it should be zero as I think Julie Olds had the first production kit of the 4".

But once again in my excitement I completely forgot to take video or photos of it then again with a wide open reg at 120psi you need to be on the coal and water most of the time.

Tell you what it doesnt half make it bark