Please Explain Gear Ratio Echo SRM 2620 verses Echo SRM 2620T

JLH52

LawnSite Member
The 2620 has a gear ratio of 1.62:1 while the 2620T has gear ratio of 2:1.

Does 2:1 mean that for every rotation of the shaft, the head itself makes 2 revolutions or is it vis versa?

I don’t understand exactly what’s happening at the head between the two different gear ratios.

Some say the 2620 is better for weekly maintenance, where as the 2620T having more torque is better for heavy dense overgrowth. It's also stated by some that the 2620 with 1.62:1ratio turns more rpms.

I'm confused, please explain.
 

Ridin' Green

LawnSite Fanatic
Location
Michigan
2 rotations of the drive shaft for every one rotation of the head takes less power to run a head like that than trying to make one full turn on the head in 1:62 rotations of the drive shaft.
 

Valk

LawnSite Gold Member
Location
KS
It really is a shame that trimmer manufacturers are using gimmicky names like 'Torque' or 'Turbo' for these gear reduction heads.

Bottom line is that the head speed will be slower for any given engine RPM compared to the non-torque/non-turbo unit, meaning that the top end head speed is reduced.
~ This 'might' be advantageous for when running w/o a guard...especially when running a longer string length.
~ This will be advantageous when running any kind of a brush blade or saw-blade.
~ This will be advantageous for cutting a LOT of dense brush w/ thicker string.

2-strokes tend to make their power higher up in the rev range, so gear reduction will put that power in a sweeter spot for when the demands for said power are increased.
 
OP
J

JLH52

LawnSite Member
Are the wide open throttle rpm's the speed of the motor or the rpm's at the cutter head? I did the following calculations assuming the wide open throttle rpm's as given in owners manual are at the trimmer head. Please correct me if I’m wrong.

According to operators manual specs for both the SRM 2620 and 2620T are as follows:

2620 gear ratio 1.62:1, wide open throttle 10,300 rpm's

2620T gear ratio 2:1, wide open throttle 11,000 rpm's

I was trying to determine difference of rpm's at head at full throttle

2620 10,300 divided by 1:62 = 6,358 rpm's at head full throttle.

2620T 11,000 divided by 2.0 = 5,500 rpm's at head full throttle.

6,358 - 5500 = 858

858 rpm's difference at full throttle between the 2620 and 2620T
 

Ridin' Green

LawnSite Fanatic
Location
Michigan
No, you have that all wrong. The engine speeds are the same as the engines are the same. the difference is down at the gear box. Many manu's give gearbox speed at a specified rpm and you can compare non T and T models easily that way.

Here is a quick example for the trimmer I use in both T and non T. Look at the output speeds in the specs.

 
OP
J

JLH52

LawnSite Member
No, you have that all wrong. The engine speeds are the same as the engines are the same. the difference is down at the gear box. Many manu's give gearbox speed at a specified rpm and you can compare non T and T models easily that way.

Here is a quick example for the trimmer I use in both T and non T. Look at the output speeds in the specs.

That's exactly what I thought, I knew the engines were exactly the same displacement, that’s why I assumed the WOT rpm's were at the gear box.

Therefore aren't my calculations correct. I did calculations based on rpm's stated in operators manual to be rpm's at gear box.

Am I correct in my calculations or am I wrong?

If I'm wrong please recalculate for me. I want to know the difference in rpm's at gear box at WOT between the 2620 and 2620T.

Thanks, Ridin Green
 

Ridin' Green

LawnSite Fanatic
Location
Michigan
That's exactly what I thought, I knew the engines were exactly the same displacement, that’s why I assumed the WOT rpm's were at the gear box.

Therefore aren't my calculations correct. I did calculations based on rpm's stated in operators manual to be rpm's at gear box.

Am I correct in my calculations or am I wrong?

If I'm wrong please recalculate for me. I want to know the difference in rpm's at gear box at WOT between the 2620 and 2620T.

Thanks, Ridin Green
They show you just what the rpm's are at the engine, then then at the output shaft which is at the gear box. There's a big difference between what they show and what you came up with as far as differences in head speed..
 

joed

LawnSite Bronze Member
Location
Toronto, Canada
Ridin Green is correct. The key figure I look at is rpm output at the shaft. That usually tells me how fast the head will spin. My Husqvarna 525LK has 6500 rpm output at the shaft. That's ok but not great. Once you start getting into the range of 7500 to 8500, then you get a fast cutting head that delivers that efficient, quick, and clean cut in typical grass you see during weekly mows. The lower rpm at the shaft produces a slower spin rate which is great if you're chopping down heavy and thick items. High torque models tend to have lower rpms at the shaft. I've never found them to be great in your day to day mowing but they do well in heavy and thick items.
 
OP
J

JLH52

LawnSite Member
Ridin Green is correct. The key figure I look at is rpm output at the shaft. That usually tells me how fast the head will spin. My Husqvarna 525LK has 6500 rpm output at the shaft. That's ok but not great. Once you start getting into the range of 7500 to 8500, then you get a fast cutting head that delivers that efficient, quick, and clean cut in typical grass you see during weekly mows. The lower rpm at the shaft produces a slower spin rate which is great if you're chopping down heavy and thick items. High torque models tend to have lower rpms at the shaft. I've never found them to be great in your day to day mowing but they do well in heavy and thick items.
Below are the specs. from operators manual for the Echo 2620T and Echo 2620 I don’t see anything telling me the rpm output at the shaft. Only gives clutch engagement rpm’s and WOT rpm's.

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Ridin' Green

LawnSite Fanatic
Location
Michigan
Like I said.... some manu's give you all the specs. Echo is one that doesn't. That doesn't mean that they do it differently than other manu's. they just don't give you all the specs for whatever reason. It seems that maybe you may have taken offense to me saying that you figured it wrong, and that you may still believe your calculations are correct? No offense was meant. You simply don't have all the info you need to figure the gear rations and final gearbox speeds. Trust me, if there was very little difference, they wouldn't offer both models as that just creates a lot of extra work and expense for them to stock and promote them etc.
 
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