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post #1 of 35 Old 04-08-2018, 11:38 AM Thread Starter
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Belt length change

I am planning on increasing the engine double pulley for the impeller from 2.75" to 3" or 3.25" on my Ariens Platinum 414cc SHO with 30" bucket. Does anyone have an idea of the required increase in belt length?

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post #2 of 35 Old 04-08-2018, 11:46 AM
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Wouldn't it add 1/4" or 1/2" depending on the pulley? I have found that in the end it will still need to be put on, see, try, remove, and try a different size by an experienced guessitimate. In belt sizes, 1/4" matters!

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post #3 of 35 Old 04-08-2018, 01:35 PM
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There's some trial and error involved, yes.

But... with the assumption that a belt uses about half the circumference of a pulley... a 2.75" pulley has a circumference of 8.64"

A 3" pulley has a circumference of 9.42"
A 3.25" pulley -> 10.21"

so... half of 8.64 = 4.32
half of 9.42 = 4.71 -> about 4/10" inch, i think you could buy a half inch longer belt and have a tensioner pick up the rest of the slack
half of 10.21 = 5.10 -> about 8/10" inch, i think you could buy an inch longer belt and have a tensioner pick up the slack


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post #4 of 35 Old 04-08-2018, 02:59 PM
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Quote:
Originally Posted by Town View Post
I am planning on increasing the engine double pulley for the impeller from 2.75" to 3" or 3.25" on my Ariens Platinum 414cc SHO with 30" bucket. Does anyone have an idea of the required increase in belt length?

================================================== ====================

Before you do anything I would use the online calculators they have for electric motors and roller chain and V belt pulley sizing where you can input all the numbers and see what drops out.

If I remember my physics correctly when you increase pulley size the output speed is reduced when maintaining the same engine speed so the impeller will be slower.

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post #5 of 35 Old 04-08-2018, 03:13 PM
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Originally Posted by leonz View Post

================================================== ====================

Before you do anything I would use the online calculators they have for electric motors and roller chain and V belt pulley sizing where you can input all the numbers and see what drops out.

If I remember my physics correctly when you increase pulley size the output speed is reduced when maintaining the same engine speed so the impeller will be slower.

the impeller will be faster thats why town is doing it
others have as well
if mr town doesnt want to keep his old pulley and belts id like to be 1st inline to score them
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post #6 of 35 Old 04-08-2018, 07:12 PM
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I'd go 1/2 in bigger on the 3" and 3/4 to an inch bigger on the 3.25
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post #7 of 35 Old 04-08-2018, 07:21 PM
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I'd go 1/2 in bigger on the 3" and 3/4 to an inch bigger on the 3.25
+1 on it
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post #8 of 35 Old 04-09-2018, 03:06 PM Thread Starter
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Thank you all for your helpful responses.

I measured my new spare belt (Ariens 07200703) using a string at 42" circumference. I cannot seem to find the belt length for that part from the internet. My original belt works fine and when I slacked off the adjustment there appears enough room for a 3" pulley. If I remember correctly I had to adjust the idler pulley to get correct belt tension when new, so the stock belt is a little long.

I have two pulley assemblies, the original platinum and a Pro. Both are 2.75" diameter and fit my engine using the Platinum bolt. The Pro allows for a longer crankshaft extension (up to 3/8" longer) to fit inside the pulley assembly and is overall an 1/8" longer than the Platinum. So I will get a machine shop to shorten the end abutting the engine wheel drive pulley by 1/8" and replace the incorporated 2.75" pulley with a 3" pulley and try that out.

If the 3" pulley works out as I think with the stock belts then I will get the Platinum pulley increased to 3.25" and look for a longer belt.

Currently the impeller speed is a little over 1100 rpm and with the 3" pulley will increase to 1230 rpm and the 3.25" pulley will give 1330 rpm.

So now to find a machine shop in my area.

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post #9 of 35 Old 04-09-2018, 03:42 PM
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Originally Posted by Town View Post
Thank you all for your helpful responses.

I measured my new spare belt (Ariens 07200703) using a string at 42" circumference. I cannot seem to find the belt length for that part from the internet. My original belt works fine and when I slacked off the adjustment there appears enough room for a 3" pulley. If I remember correctly I had to adjust the idler pulley to get correct belt tension when new, so the stock belt is a little long.

I have two pulley assemblies, the original platinum and a Pro. Both are 2.75" diameter and fit my engine using the Platinum bolt. The Pro allows for a longer crankshaft extension (up to 3/8" longer) to fit inside the pulley assembly and is overall an 1/8" longer than the Platinum. So I will get a machine shop to shorten the end abutting the engine wheel drive pulley by 1/8" and replace the incorporated 2.75" pulley with a 3" pulley and try that out.

If the 3" pulley works out as I think with the stock belts then I will get the Platinum pulley increased to 3.25" and look for a longer belt.

Currently the impeller speed is a little over 1100 rpm and with the 3" pulley will increase to 1230 rpm and the 3.25" pulley will give 1330 rpm.

So now to find a machine shop in my area.
I have done alot of research on your belt part number mr town as thats the belt i will be getting if upgrade to sho top pulley
no place could i find the length on the net
I found it on rock auto says 41.125 od
https://www.rockauto.com/en/moreinfo...=4970133&jsn=3

My blower has the 2.5 stock you are 2.75
2.5 impeller rpm 1010
2.75 impeller rpm 1083
Think you are a lil high at 1230 think you will pick up around70 to 75 for 3 inch 140 to 150 for 3.25
3.25 would be the way to go imo
The length of the top pulleys are not the same you show a washer with your sheave mine does notyou say the pro is not the same as yours interesting
cant see that the crank is longer 414 should be 414
you would think being a larger pulley woudnt matter

Last edited by 1132le; 04-09-2018 at 03:49 PM.
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post #10 of 35 Old 04-09-2018, 06:11 PM Thread Starter
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Originally Posted by 1132le View Post
I have done alot of research on your belt part number mr town as thats the belt i will be getting if upgrade to sho top pulley
no place could i find the length on the net
I found it on rock auto says 41.125 od
https://www.rockauto.com/en/moreinfo...=4970133&jsn=3

My blower has the 2.5 stock you are 2.75
2.5 impeller rpm 1010
2.75 impeller rpm 1083
Think you are a lil high at 1230 think you will pick up around70 to 75 for 3 inch 140 to 150 for 3.25
3.25 would be the way to go imo
The length of the top pulleys are not the same you show a washer with your sheave mine does notyou say the pro is not the same as yours interesting
cant see that the crank is longer 414 should be 414
you would think being a larger pulley woudnt matter
Thanks for your input.

Hard to believe that I made a mistake of an inch in measuring the outside circumference of the stock belt. Not sure how I can verify my discrepancy.

The 1083 rpm with the 2.75" pulley is at 3,600 rpm but Ariens allow a 100 rpm variance + or - so I am running 3,700 rpm which is about 1130 rpm by calculation and with my infrared laser rpm meter. Each 1/4" increase from 2.75" at 3,700 rpm (with a 9" impeller pulley) gives slightly over 100 rpm increase. So 1233 and 1336 respectively with the 3" and 3.25" pulleys by calculation method. Not being a mathematician I rely on an app for that. The problem is that the effective pulley diameter is not its outside measurement but the belt path which is considered to be about 1/2 the belt depth so a 1/8" or so less. So that is why the Platinum is rated 1083 compared to the calculated 1100 rpm at 3600 rpm. As the belt wears it drops a little in the groove so speed drops marginally. My setup is measured at a little over 1100 rpm for the impeller actual speed, but at higher engine speed. My issue is that the Pro spec is over 1112 rpm with the same size components as the Platinum, which cannot be the case.

The B&S 420 engine uses a longer crank extension than the LCT 414 engine. There is no washer between the LCT engine impeller pulley assembly and the engine wheel drive pulley. The Pro engine impeller pulley has a deeper 1" opening with an included keyway that fits over the crank on the B&S 420 engine. So the Platinum pulley will not work on the B&S engine but the Pro pulley will work on the Platinum. To get the best pulley alignment the Pro pulley needs to be shortened by 1/8".

Hope this explains my numbers better.

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