Adjusting drive axle rpm for re-powering - Snowblower Forum : Snow Blower Forums
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post #1 of 12 Old 01-04-2019, 06:19 PM Thread Starter
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Adjusting drive axle rpm for re-powering

Hi everyone, new member here, first post and question. I've spent several hours cruising the site and am impressed with all of the knowledge.

Looking at re-powering an Atlas A825TG (1989 vintage) blower that has a blown dual shaft TEC HM80. I've looked at can't find a decent one to replace it with so I'm leaning towards the Predator 301cc which of course is a single shaft.

If I'm using the pulley calculator correctly, the TEC is currently turning the auxiliary PTO at 1800RPM at the engine and delivers ~720RPM to the drive shaft which drives the Trac Drives (wheels). Small pulley diameter is 2", large is 5", center to center is 9".

The Auger set up will be fine with an engine swap.

What's the best way to lower the RPM for the Trac Drives (wheels) off of the new single shaft engine which is 3600RPM. Best I can figure is new pulleys but even using 6" and 3" my RPM to the drive would still be high at 1800RPM.

Oh, and the Atlas is a bit unique in that the friction disk switch lever (reverse to forward) is not centered as I've seen on others so I have already flipped the friction wheel and done some other mods to get it to work in the correct direction anticipating using a single shaft motor.

Maybe smaller pulleys on the auger, larger on the wheels and then governor down the engine. Or a combination of both. The track drives have internal gears and are chain driven, maybe doing some mods there could help also.

Appreciate any advice, I have not bought the engine yet, just have killed some time doing the other work while on vacation.

Mark


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post #2 of 12 Old 01-04-2019, 08:48 PM
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to SBF Mark

If you reduce the governors RPM you also reduce the machines ability to move snow when it's thick and you need it most.
I know it can be done but I'd be looking for a dual shaft engine rather than trying to put all that time into trying to convert it to a single shaft. Is this you're only blower ??

When you say "blown" is the block cracked or is there a hole in it over on the starter side ??

They do come up on Ebay, craigs, facebook - - > https://www.ebay.com/p/Tecumseh-MTD-....c100009.m1982

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Make sure the windows are up before the snow plow goes by !!

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post #3 of 12 Old 01-06-2019, 11:31 AM Thread Starter
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Thanks Frog, I actually have a small electric blower which works well on our deck and walkways. I also am picking up a tractor with a bucket this week for pushing snow.

This is just a project to keep myself busy and I'm already committed to a single shaft with the other work I've done. I've adjusted the friction wheel to where it is barely past the center point of the drive disk for low speed, forward position #1. That with a bigger pulley should work out. In the picture attached (prior to reversing the drive) the friction wheel is in the old reverse position #2, with the changes I've done that is now forward position 4 of 6. Forward position 1 as I mentioned is just barely to the left of the center of the drive disk.

The 8hp TEC never really had enough power so I'm looking at either a 250cc Briggs or a 301cc Predator. Just need to make sure I can get the correct size belts before I pick up the engine.

Mark
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post #4 of 12 Old 01-07-2019, 09:53 AM
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post #5 of 12 Old 01-07-2019, 10:44 AM
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what about one of these? they are a bit more money but should solve your issue about the axle drive speed
https://www.brandnewengines.com/15C194-3018.aspx

arien 520 snow blower 6.5hp swap
yardworks 31AH6WKF515
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post #6 of 12 Old 01-07-2019, 11:30 AM
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Just my 2 cents on this issue.


The end game would be to get the same (or nearly the same) RPM ratio of the drive disc as compared with the impeller shaft. If you figure out the ratio that you are getting with the 2 shaft engine at the shafts, then maybe you can achieve the same ratio from the single shaft with both a small and a larger pulley, leaving the other pulleys within the chassis the same.


If not, then you may have to do a combination of mixing/matching both the engine output shaft pulleys and the chassis pulleys to get the same final ratios. The fewer pulleys to change the better.


As mentioned, using the governor would not be a good approach, because you will be slowing down both the wheels and the impeller, and reducing the throwing power accordingly.

Regards, Ted
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post #7 of 12 Old 01-09-2019, 08:18 PM
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looks similar to mine, i swapped to a harbor freight 212cc, changed both pulleys. pic was taken before large pulley was swapped, you can see the sping on left i had to turn around to get more movement of drive wheel, there may have been a pin i had to knock out to get it to slide over that far
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post #8 of 12 Old 01-09-2019, 08:28 PM
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If you won't be able to get the speed down to stock-ish, then I'd plan to go a bit big on the engine and pulley for higher impeller speed. That'll increase the snow processing speed (provided you've got enough engine power) and make the somewhat fast drive speed less of a problem (as you'll be able to move faster before the machine can't keep up).
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post #9 of 12 Old 01-20-2019, 11:42 AM Thread Starter
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Thanks for all the advice, I had already done exactly as aweks has suggested including knocking roll pins out to allow for more movement, I also had to put spacers in on the rubber friction wheel to get it to reach the outside edge of the drive wheel. In researching pulleys I just couldn't get the ratio and rpm I needed so after further consideration I'm going with crazzywolfie's suggestion on a brand new two shaft motor. I really did not know these were still available but I was looking for 8hp. I think the 11hp, as long as it fits, will do great.

Ordering today and have already unengineered the changes I had made.

I'll let you know how it turns out.


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post #10 of 12 Old 01-20-2019, 12:16 PM
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i am pretty sure the engine i linked to should be about equivalent to a 8hp or maybe 9hp. it is only a 250cc engine. it is 11.50 ft/lbs of torque. if it is anything l like the 250cc engine on my 26" machine i think you will be pretty happy with it. i find it pretty good on fuel and pretty powerful. i just wish mine had the throttle and fuel shut off like those engines. it was someone else on this forum that originally linked to that engine only a coupe months ago which is why i knew they were still available.

there is a chance you may need a adapter sleeve to go from 3/4 to 1" output shaft. you may want to try pulling the pulleys off the old engines to check that so you will know if you need the adapter or not.

arien 520 snow blower 6.5hp swap
yardworks 31AH6WKF515
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