Torque

[Swisher]

Looking at the specks for the jd2520 it says 51.3 torque at 2600 rpm.
Formula for Torque=5252xhp/rpm
When I clculated the formula it comes up to 53.53 ft lb, subtract the 51.3 ft lb from the spec have difference of 2.23 ft lb, which I think is drive line loss.

My question is if I run the tractor at 1800 rpm will I get 77.23 ft lb minus the 2.23 ft lb for drive line or will the tractor only put out the 51.3 ft lb as discribed in the specks.

 

[JCB]

Swisher,

Using your formula, I'd suspect the horsepower drop at 1800rpm would negate most the drop in rpm.

Joe

 

[orlo]

Swisher:

One of the specs is wrong. Both HP and torque at at the engine.
But your 73 calculation looks like you were assuming 26+hp at 1800RPM
which is incorrect - it would be less than the max HP. You'd need to look at a torque curve of the engine
to know what the torque would be at 1800rpm. (or an HP curve and you could calculate the Torque). It will be far less than 73 but probably slightly more than 51.3 I noticed the specs don't list 'max' torque, just torque at the rated RPM..

Generally on Diesels the torque curve peaks low (1600/1800rpm) and then goes down slightly until the maximum RPM. Max HP is always at a equal or higher RPM than max torque (Always higher on Diesels. You might find a two stroke dirt bike where they are virtually the same).

John Deere might be able to tell you the 'engine' torque at 1800rpm.

 

[Swisher]

Thanks Orlo, I am begining to see it now. The HP for JD2520 is 26.5, now I understand that the lower the rpm the less Hp.

Thanks again.

 

[73jeep]

Just out of sheer estimating and guesswork, I'll bet your max torque would be around 56-61 ft/lbs. And this would be in the neighborhood of 1800-2000 rpms. I only base this on similiar sized engines that specify max torque instead of torque at rated eng. speed.

 

[Swisher]

Thanks for the replys, I just trying to get a estimate of about were to set the rpm for loader work.

Thanks Again,



Bert

 

[therebarely]

If my memory serves me, horsepower includes a time element, whereas torque calculations do not have a time element. Horsepower is the amount of work performed in a prescribed amount of time. Someone correct me if I am wrong.

 

[orlo]

Therebarely:

Generally HP listed is instantaneous HP which remains constant over time but you are right. HP is the ability to do a certain amount of work in a certain amount of time.

One SAE HP is the ability to lift (Straight up [and with Earths gravitational pull]) 33,000lbs 1 foot in 1 minute [or 1lb 33,000 feet in one minute or any combination multiplying out to 33,000]. This is 33,000 foot lbs of work. If you put ft lbs of work into a circle you get a 1 foot lever going around the center (A unit circle) who's circumference (PI * the diameter[2]) is 2PI so you get 2PI (2*3.1415926...) foot lbs of work every revolution.

33,000 divided by 2PI is 5252. So with 1ftlb of torque if you can spin 5252RPM you've generated 1hp.

Thus to compute HP if you know torque and RPM it's HP = RPM * Torque (in Ft/lbs) / 5252.

If you only know torque or RPM and not both RPM you cannot compute HP.
Given any two (HP, Torque, or RPM) you can compute the missing one.

If torque remains the same, a higher RPM produces higher HP. But torque in diesel engines generally peaks early and then slowly goes down as the RPM goes up.

 

[psdx]

Just out of sheer estimating and guesswork, I'll bet your max torque would be around 56-61 ft/lbs. And this would be in the neighborhood of 1800-2000 rpms. I only base this on similiar sized engines that specify max torque instead of torque at rated eng. speed.

I beleive this is the hp/torgue curve for the 2520 engine: http://www.yanmar.com/file.asp?F=1F...2A-DSA+performance+curve-DI.pdf&C=store_items

It shows a peak of 64 ft-lb at 1200 rpm