How much torque?

[rcn11thacr]

I have not had any luck finding torque figures for my motor so I'm asking here for assistance. I have a 27 hp Kawasaki in my max Iv, can anyone tell me how much torque this motor makes? Also, how do I figure that torque figure as it goes through the T-20? That is, what would the figure be after it goes through the tranny (and before it gets to the sprocket)? Finally, what would the torque figure be at each axle assuming at 12 tooth sprocket on the T-20?

[msafi65]

27 hp Kawasaki was listed at 43 ft.lbs. of torque. This was my favorite MAX engine. It's only 1.6 ftlb under the kohler aegis at 31 hp. The t20 is 6.25:1 but I don't know how you figure belt and clutch slippage and variable ratios there. Hope this helps a bit.

[Mike]

Here is a link to a photo of an excel sheet I was using to determine what tooth count I wanted when gearing my Argo:


Like msafi65 mentioned, there are several variables that are difficult to calculate because they are constantly changing through the RPM range. There are a lot of good sites in the golf cart / go kart world that have information on calculating those figures if you are interested but I cheated and treated the CVT system as 1:1. That simplifies everything. The reason I did this is that I was targeting the same gearing in my Max IV and the CVTs could be eliminated in the calculations since they both had similar CVTs.

If you walk through your gearing, start with the T20 which msafi65 mentioned was 6.25:1, meaning that you get one revolution on the output shafts for every 6.25 revolutions of the input shaft. If we go with your output sprockets of 12 teeth and assume that your axle sprocket on the rear is 32 tooth, then your gear reduction at the axles would be (1/6.25)(12/32)= 0.06 So for every 1 RPM of the T20 input shaft, you have 0.06 revolutions of the axle. If you take the inverse of 0.06 (or 1/0.06) you get a gear ratio of 16.67:1

So take your input torque of 43 ft-lbs and multiply it by 16.67 and you get 716.81 ft-lbs at the axles

Hopefully someone else can correct anything I missed?

[amphibious drew]

Here is a link to a photo of an excel sheet I was using to determine what tooth count I wanted when gearing my Argo:


Like msafi65 mentioned, there are several variables that are difficult to calculate because they are constantly changing through the RPM range. There are a lot of good sites in the golf cart / go kart world that have information on calculating those figures if you are interested but I cheated and treated the CVT system as 1:1. That simplifies everything. The reason I did this is that I was targeting the same gearing in my Max IV and the CVTs could be eliminated in the calculations since they both had similar CVTs.

If you walk through your gearing, start with the T20 which msafi65 mentioned was 6.25:1, meaning that you get one revolution on the output shafts for every 6.25 revolutions of the input shaft. If we go with your output sprockets of 12 teeth and assume that your axle sprocket on the rear is 32 tooth, then your gear reduction at the axles would be (1/6.25)(12/32)= 0.06 So for every 1 RPM of the T20 input shaft, you have 0.06 revolutions of the axle. If you take the inverse of 0.06 (or 1/0.06) you get a gear ratio of 16.67:1

So take your input torque of 43 ft-lbs and multiply it by 16.67 and you get 716.81 ft-lbs at the axles

Hopefully someone else can correct anything I missed?

My head hurts after reading that the day before a holiday.

[Noel Woods]

I think Mike's data is solid.

Of course, air cooled engines are notorious for losing compression, and that effects both Horsepower and torque. Lets just say you have lost 10% of each over the years, that would still leave a very respectable power to weight ratio any way you cut it. Especially in a machine that weighs just over 1200 pounds with a load and driver.
Then you get into tractive force which is not measured well diagnostically. Then the issue of power loss via parasitic load, etc. There are many variables that you could look into, but the calculations get deep.

Bottom line though your machine is one of the most capable amphibs produced, so I'd just rock and roll on with it.

[rcn11thacr]

So take your input torque of 43 ft-lbs and multiply it by 16.67 and you get 716.81 ft-lbs at the axles

Mike,
So for clarification, that would be 716.81 divided by 6 axles right? So it's 119.46 ft-lbs per axle.

[rcn11thacr]

Thanks to everyone for help with my questions.

[anotheramature]

My guess is that you would divide by 3 beings that output shaft is driving only 3 axels the other output shaft drives the other 3 axels... Right?

[Mike]

Mike,
So for clarification, that would be 716.81 divided by 6 axles right? So it's 119.46 ft-lbs per axle.

My guess is that you would divide by 3 beings that output shaft is driving only 3 axels the other output shaft drives the other 3 axels... Right?

I would say that you are both right. With the T20, you can split the torque/power to both sides or have it all (for the most part) going to one side so I would think that it would vary between 1/3 to 1/6 of the full torque. However, keep in mind that traction is also a factor. If you have one tire one dry ground and the other 5 in the mud, it can be possible to apply a lot greater torque to that one axle. It really depends on what you are trying to do with the torque values that you calculate.

Also, if you are trying to find the torque transferred to the ground at each axle, don't forget to factor in your tire size as well.

[riotwarrior]

If...IF uou know your clutch type a d can locate ratio info you can determine Hi and Low as well like slight downhill grade wide open throttle provides different than steep uphill wide open...thus the torque is much different too! up to 4 x more torque in low than hi...just saying there are lots of parameters to consider

JM2CW

[rcn11thacr]

Well, it appears my questions have opened up a can of worms...

Mike you posted this: if you are trying to find the torque transferred to the ground at each axle, don't forget to factor in your tire size as well.

How does tire size factor into this, literally?

Riotwarrior, same to you. I'm not sure how to factor that into the equation either.

[Mike]

I think the real question is, what are you really trying to calculate and what are you wanting to use that data for?

Both the tire diameter and the clutch ratio will be factored in just like the previous gear ratios were. For the CVT, you can look your specific model up online and get the actual ratios, both starting and final drive ratios. The starting ratio will be the highest torque and the final ratio will be the lowest torque. If you find out that your starting ratio is 4:1, then your torque right off of idle is 4 times greater there. If your final drive ratio is 0.5:1, then your final torque at top speed is divided in half there. Anything in between is variable between those two numbers. We previously assumed a 1:1 to make the calculations easier because you are using the same clutches for whatever gear ratios you choose so it really doesn't matter.

For the tire diameter, the larger the tire, the lower your applied torque will be. A smaller tire will apply higher torque to the ground. Or you can look at it that a larger tire will take more torque to turn. So, treat them just like you would a gear ratio, just do so in inches instead of teeth. So, if the diameter of your 32 tooth sprocket is 7" and the diameter of your tires are 26", then your tire ratio to factor into our earlier equations is 7/26. That means that the torque is decreased at the tire. If your torque at the axle is 100 ft lbs, then at the tire, it would be 26.9 ft lbs.

I'm just typing this out loud. Please question my math and be sure to Google anything I'm typing for verification. There are a lot of good free torque calculators online that will make life much easier for you if you search for them. There are also a lot of detailed equations on many 4x4 sites that can help as well.

[riotwarrior]

what I will say is find my muscateer thread in other atv section start at the end ang go backwards. Find the math I did to calculate overall gear ratios and for your application input the specifics and you can determjne final output...dont forget about parasitic loss through drive train no less than 10%

what is it you plan to do with the data btw?