Author Topic: Engine swap - Snowblower  (Read 8527 times)

Offline Brass_Machine

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Engine swap - Snowblower
« on: October 26, 2016, 12:59:27 AM »
Hi all,

For those of us in the colder part of the world, we all know, winter is coming... That means that it is time to get the snowblower tuned up.

Back story: A few years ago, when I moved into the new house, I looked at the drive and figured I could just shovel it myself... "oh, it will be a good workout!" Yeah right. The driveway is about 350 to 400 ft. We had a brutal winter that year. A lot of snow... after the first snow fall and subsequent shoveling, I immediately went on Craigslist and found a snowblower. It is an Ariens ST420. A 2 stage 4 HP blower from the late seventies. Ad said, it ran last year but would not start so instead of fixing it, the owner bought a new one. $70. So I went and looked at it. Gave a tug on the starter and while it turned over, it would not start. So I offered the guy $25 for it and loaded it into my truck.

Got it home, cleaned it the best I could (it snowed the next day) and fire some starting fluid into the carb . It fired right up. Used it that winter by sarting it every time with starter fluid. The next winter I went to order a carb rebuild kit for it an found a new carb was only a few dollars more. Ordered it and put it on and had an easier time using it. This past winter, the motor seemed to have less power. Thankfully, we didn't get anywhere near as much snow, but it kept stretching belts because it did not  have the power to move the snow etc...

This year, I have decided to give it a new heart. I am replacing the original 4 HP engine with a 6.5 HP Honda clone. The replacement engine has good reviews and even has a go kart racing culture popping up around it. Apparently, with some hop up parts, I can get 27 HP out of it  :headbang:

So here is the start. The blower in it's current state (I had already started dismantling it):



This is the 6.5HP Predator engine I am putting in:



No adjusting or adapter plates required. It fits perfectly into place. Almost like it was meant to be there.



Comparing the engines output shafts, they are the same diameter and located about the same height from the bottom of the engine:



The crank pulley even fits nice!



But now we see the first problem. Anyone see it?



Yup, the eagle eyed will  see that the old engine has 2 output shafts, not just one. The old engine has a pulley that comes off the cam that rotates in the opposite direction from the crank output shaft.

While I can get a pulley from a new model that is essentially a double pulley, it does require an adapter sleeve (3/4 to 1"). Not really a problem to buy (going to order it tomorrow) The real issue is that pulley that spins in the opposite direction? It drives the wheels. So if I don't do anything, I will have 1 forward speed and 4 reverse speeds!  :doh:

So now I have to figure out how the drive train works. The belt drives a spinning disc, when you pull the drive lever, it pops up and makes connection to a dirve wheel which in turn drives the wheels. When you select a speed, there is a U shaped fork that slides the wheel to a different position above the disc. The closer it is to the center, the faster it spins, driving the wheels at a higher speed. At its slowest speed, it is towards the outside of the disc thus spinning slower. Move it into reverse and it goes past the center of the disc and spins in the opposite direction.

I pulled the contact wheel and shaft to have a closer look.



I forgot to take a picture of it in the blower chassis. You will have to imagine a spinning disc (much like a record, remember those?) perpendicular to the big wheel.

Took it apart to get a better understanding:



At first, I thought I could just reverse everything. Nope. Can't do that. The big drive gear (not pictured) will not fit on the other side. Too much in the way. I have to either come up with a way to spin the drive platter (for lack of a better term) in the opposite direction or add an intermediate gear to spin the wheels in the opposite direction.

Hmmm. Another idea might be to move that drive wheel down the shaft so it would work in reverse?  :scratch:   :smart: There are some things in the way, I might not get full movement. Maybe go from 4 forward speeds to only 2... I only use 2 speeds anyway. The lower ones... if i push the drive wheel past the center of the platter, I would only get the higher speeds. I think I have that right.

I will try to get pictures of the guts to explain what I mean tomorrow.

Until then I will be  :scratch: trying to figure this out.

Eric


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Offline awemawson

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Re: Engine swap - Snowblower
« Reply #1 on: October 26, 2016, 02:43:02 AM »
Eric,

Can you not make a flat gearbox that bolts on round the main shaft and has a 2:1 ratio presenting a shaft where your missing one is and running at the correct speed and direction?

I imagine a sort of sandwich arrangement, two flat plates and a spacer a little fatter than the gears, suitable bearings for the new shaft, and filled with a little oil.
Andrew Mawson
East Sussex

Online wgw

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Re: Engine swap - Snowblower
« Reply #2 on: October 26, 2016, 05:20:58 AM »
I don't know these machines , is there room to put a twist in the drive belt to the wheels ?

Offline RussellT

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Re: Engine swap - Snowblower
« Reply #3 on: October 26, 2016, 05:47:40 AM »
I might be misunderstanding your description but it sounds as though the spinning disc axle is vertical and the camshaft is horizontal.  How is the drive turned through 90 degrees?  Is there an opportunity there?

Russell

Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #4 on: October 26, 2016, 09:11:26 AM »
I might be misunderstanding your description but it sounds as though the spinning disc axle is vertical and the camshaft is horizontal.  How is the drive turned through 90 degrees?  Is there an opportunity there?

Russell

Hi Russell

I will get some pictures today... a picture is worth a thousand words  :thumbup: it will explain much better than I can.

Eric
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Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #5 on: October 26, 2016, 09:13:04 AM »
I don't know these machines , is there room to put a twist in the drive belt to the wheels ?

I have thought about that one. Wouldn't there be wear from the belt rubbing against itself?
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Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #6 on: October 26, 2016, 09:17:32 AM »
Eric,

Can you not make a flat gearbox that bolts on round the main shaft and has a 2:1 ratio presenting a shaft where your missing one is and running at the correct speed and direction?

I imagine a sort of sandwich arrangement, two flat plates and a spacer a little fatter than the gears, suitable bearings for the new shaft, and filled with a little oil.

I think this one is possible. The new engine does have the 2 extra bolt holes at the top... I am having a hard time seeing in my mind what you are describing. I think I know but I am not sure...
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Offline awemawson

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Re: Engine swap - Snowblower
« Reply #7 on: October 26, 2016, 09:40:15 AM »
Eric, a quick C o Cad sketch

The cam shaft goes half the speed of the crank shaft so you need a pair of gears with a 2:1 tooth ratio. Drill the rear plate to pick up the mounting hole around the existing shaft. Gasket paper between the plates and drill an oil filling hole somewhere
Andrew Mawson
East Sussex

Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #8 on: October 26, 2016, 10:04:24 AM »
Here is a view looking from the bottom up.



I left of the gear that drives the wheels on the left. I believe the drive wheel is positioned between 1st and 2nd. I believe I have it wrong... the closer the drive wheel is to the center of the platter, it spins the wheels slower. The closer to the edge, the wheels spin faster.

If I adjust the drive wheel so it contacts the other side. I will get 1st and 2nd plus 1 reverse speed.Unfortunately, it cannot go any further left due to things being in the way.



Eric
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Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #9 on: October 26, 2016, 10:08:31 AM »
Eric, a quick C o Cad sketch

The cam shaft goes half the speed of the crank shaft so you need a pair of gears with a 2:1 tooth ratio. Drill the rear plate to pick up the mounting hole around the existing shaft. Gasket paper between the plates and drill an oil filling hole somewhere

That looks like it could be a good solution. I would just have to find gears that would work as I am not setup to cut my own gears.
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Offline Manxmodder

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Re: Engine swap - Snowblower
« Reply #10 on: October 26, 2016, 01:20:33 PM »
Eric, a quick C o Cad sketch

The cam shaft goes half the speed of the crank shaft so you need a pair of gears with a 2:1 tooth ratio. Drill the rear plate to pick up the mounting hole around the existing shaft. Gasket paper between the plates and drill an oil filling hole somewhere
Would the timing gears in the timing case of the old engine fit the bill? They are up to the job on the old engine they should be fine in Andrew's suggested gearbox.....OZ.

That looks like it could be a good solution. I would just have to find gears that would work as I am not setup to cut my own gears.
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Offline RussellT

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Re: Engine swap - Snowblower
« Reply #11 on: October 26, 2016, 01:57:12 PM »
Thanks for the extra picture. That helps.

Could you add an extra cross shaft carrying the gear that engages with the large gear and fit two gears at the other end of the shafts to reverse the direction?

Or would it be possible to replace the large gears with a chain drive - although you'd probably need an intermediate shaft and sprockets somewhere to get the ratio right.

Or raise the engine up and put a couple of shafts below it and deal with reversal there.

Incidentally there ought to be a couple of suitable gears in the old engine - but that would mean you couldn't go back.

Russell


Offline awemawson

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Re: Engine swap - Snowblower
« Reply #12 on: October 26, 2016, 01:58:21 PM »
Shame to spoil a perfectly good engine though - stock gears are cheap enough
Andrew Mawson
East Sussex

Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #13 on: October 26, 2016, 03:18:52 PM »
Shame to spoil a perfectly good engine though - stock gears are cheap enough

Yup. Gonna keep the old engine for a bit. I will use your idea of a flat gear box. Need to design it and find gears that work...
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Offline seadog

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Re: Engine swap - Snowblower
« Reply #14 on: October 26, 2016, 03:27:31 PM »
What about turning the drive hub around on the shaft? It would mean relocating the actuating fork though. Is that feasible do you think?

Offline vintageandclassicrepairs

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Re: Engine swap - Snowblower
« Reply #15 on: October 26, 2016, 04:19:09 PM »
Hi,
You will need to incorporate a 2;1 reduction as the drive from the camshaft was at 1/2 the crankshaft speed
So moving the drive disc across the the other side will work, but it will be twice the speed it was with the old engine :Doh:

"Neracar" 2 wheelers from the 1920's used a similar drive with the drive roller running against the engine flywheel !!!!!

I use "kevlar" belts on my ride on mower, much less prone to wear /slippage, I dont believe belts stretch much they wear on the sides and sink further into the pulleys ???

John

Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #16 on: October 26, 2016, 11:19:04 PM »
What about turning the drive hub around on the shaft? It would mean relocating the actuating fork though. Is that feasible do you think?

That was my initial thought and perhaps the easiest fix. Problem is, there is stuff in the way and I would not get full movement (so not all the forward speeds) plus the drive pulley spins at 1/2 RPM... spinning it directly off crank would double all the speeds.

Eric
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Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #17 on: October 27, 2016, 12:04:06 AM »
So, I am searching for gears.

Having the worst time. I cannot find keyed gears that have the same pitch angle for both 1/2" and 3/4" shafts. the crank shat is 3/4" while the pulley that drives the wheels (originally off the cam) is only 1/2".

The only thing I have found so far is some gears that can be bored. No keyway though... Which is fine for the 1/2 drive shaft, I need a keyway for the 3/4 shaft.

Hmmmm
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Offline awemawson

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Re: Engine swap - Snowblower
« Reply #18 on: October 27, 2016, 02:22:01 AM »
Come on Eric, we're mad modders, you can slot a key way on your lathe, or if your lathe is too skimpy for that, I'm certain one of our fellow members can do it for you.
Andrew Mawson
East Sussex

Offline RussellT

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Re: Engine swap - Snowblower
« Reply #19 on: October 27, 2016, 05:42:52 AM »
If I adjust the drive wheel so it contacts the other side. I will get 1st and 2nd plus 1 reverse speed.Unfortunately, it cannot go any further left due to things being in the way.

I think I would give this a try first.  As this is a continuously variable transmission 1st, 2nd etc are just positions so by holding the gear lever in position 1/2, 1, 1 1/2 and 2 should give you 4 speeds.  Because the disc is running at double speed they should be equivalent to 1,2,3 and 4.

It may not work because the higher disc speed may cause slipping but I would have thought it was worth a try.

Russell

Offline Manxmodder

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Re: Engine swap - Snowblower
« Reply #20 on: October 27, 2016, 05:44:11 AM »
Shame to spoil a perfectly good engine though - stock gears are cheap enough

Yup. Gonna keep the old engine for a bit. I will use your idea of a flat gear box. Need to design it and find gears that work...

I misunderstood your earlier posts and thought the old motor was a scrapper. I also would feel hard of dismantling a motor for the gears if it was still a runner.

Looking back to where the suggestion was taking us why not find another engine that is a scrapper from a mower or similar and whip the gears out of that.

Thinking a little further along these lines,if the gears,crankcase and the front cover could be acquired from a knackered Honda model that yours is the clone of then the crankshaft is the same diameter and you have the extra front cover with the same bolt hole pattern as your new engine to make the front cover for your gearbox. You only need to make a back plate if you slice an end section of the scrappers crankcase......OZ
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Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #21 on: October 27, 2016, 12:47:55 PM »
Come on Eric, we're mad modders, you can slot a key way on your lathe, or if your lathe is too skimpy for that, I'm certain one of our fellow members can do it for you.

Yeah yeah. I don't know if my tiny lathe can handle it, but I am going to try. I have never slotted a key before, so this will be new territory for me. I figure if I can't get it cut, I will just cut the key down (So I can still use it for the impeller pulley) and just use a set screw or two to hold it in place. Going to order the shaft and two gears today.
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Offline awemawson

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Re: Engine swap - Snowblower
« Reply #22 on: October 27, 2016, 01:20:18 PM »
A perfectly acceptable keyway can be made by:

a/ turn a plug to be a tight fit in the bore of the gear

b/ drill a hole slightly smaller than the width of the keyway so half is in the plug and half in the gear

c/ remove plug and hand file embryo keyway out to full size using a four square file

It actually doesn't take long as the drilled hole removes a lot of the material and acts as a guide
Andrew Mawson
East Sussex

Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #23 on: October 27, 2016, 01:30:20 PM »
Thanks Andrew! I will give that a shot. Always willing to learn something new.

I ordered the 2 gears. Got a 24 and 48 tooth gear, 6" piece of 1/2" drive shaft and a couple of bearings. Should be here tomorrow. I need to get this done and working, I think, fairly soon. We already got freezing rain this morning! :doh:

Not sure if I will have time to work on it this weekend. I might have some time to work on the design of the mount. Do it up on cad... have to figure out where to have the pulley placed so I don't need to buy a different length belt.

Eric
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Offline Brass_Machine

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Re: Engine swap - Snowblower
« Reply #24 on: October 27, 2016, 04:43:19 PM »
Dumped some the rusty pulleys and the drive shaft into a vat of Apple Cider Vinegar to de-rustify them.

Just waiting on parts.

Eric
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