PTO electric clutch help!

[ArlyA]

electric PTO clutch and shaft size help!

I'm assembling a mini tiller what is used within the cross country ski industry to chew up hardened snow. There are a few made in the EU, but these do no fill the needs here in North America and are toooooooo narrow or under powered in general. The one I've been asked to assemble with be 6ft wide and be powered by a v-twin engine, putting out 37 or so HP. The HP per foot is already been established by the alpine industry, so I'll stick with those approximate numbers. The engine's we're looked at come either with a 1 and 5/16 or 1 and 1/8 output shafts.

In the below print, you can see a jack shaft that bring the power out to the implements end and connect to chain box that will of course run the tiller. The tiller will need to be ran at 1000 RPM, give or take so will need be a 3 to one reduction. Off the engine, we've like to use a couple of 5vx belts to power the jack shaft off the engine. Here on the jack shaft, we'd like to utilize an electric PTO clutch that can used with dual, 5vx belts. Two questions for you mechanical gurus here are below.

Would a 1 and 1/8 size mild steel jack shaft be sufficient if its 2 to 4ft long? Engine will be position so as to balance the implements weight so the jack shafts length is not know at this time.. An where can we find a PTO clutch we can use and has 2 belts and can be used with a 37 HP engine. Obviously it needs to be 12 volt and no brake is needed. Start up will be at idle or low RPM and system inertia is hard for me to describe. I guess it would be like a 6ft wide dirt tiller. Options????

 

[ericm979]

Torque on the clutch will be a limiter. You can put it on the engine side if you can't find one strong enough to handle the torque after the gear reduction. Could you use an operator operated belt tensioner as the clutch, like some riding mowers?

 

[leonz]

Once you start digging that tiller will act like a vacuum and it will just skip over the surface as you are essentially trying to dig in gravel pavement.

you need to know is that placing the engine in the center with the jack shaft is counter productive and wastes power as the best way to run a tiller is with chain drive using the engine on the end of the tiller over the driven gear to provide the power needed. The belt drive will not work well as it will slip too much.
Before you go too far you need time to you run the purchasing and labor numbers and you will find that purchasing two of those units and having them shipped here in 6 weeks will be simpler and much less costly.

You will be able to make tandem hitch for them with a little overlap and cover almost six feet at a pass so the speed will not be an issue and repairs will be easier to do. Even if yopu add a third unit you will be able to groom a little less than nine feet with a three unit tandem hitch.

 

[ArlyA]

Torque on the clutch will be a limiter. You can put it on the engine side if you can't find one strong enough to handle the torque after the gear reduction. Could you use an operator operated belt tensioner as the clutch, like some riding mowers?

I already drew the prints up for an actuator operated idler on the two v belts. That is a very doable design, but if the machine operator "suddenly" finds that hidden stump banging against the tiller, a PTO style electric clutch would be a more of a immediate disconnect of the tiller, from the engine. They do make them for this much torque/hp and they even have them on many compact tractors. I did email Warner asking them what they offer, but no response as of yet...

 

[muddstopper]

Warner makes multiple vbelt clutches, you will need to give them the torque and hp numbers you will be imputing before buying one. There is also another company call Extreme that makes quality electric clutches and they are much cheaper than Warner or Ogrua. There clutch pullyes are made out of billet aluminum and I have used them with good results. They also have a one year free replacement warranty. The mention of going with gear and chain drives I am opposed to. Anything that is going to be subjected to shock loads, belts are a lot more forgiving than chains and gears. I wouldnt worry about belts slipping, stump grinders and straw blowers use belts all the time. Better to slip a belt than break a chain.

 

[ArlyA]

Thanks Mudd, that was very helpful! I knew that Warner makes PTO clutches large enough and I did send them an email asking for specifics, but sometimes these large companies never respond. To busy for customers? I will now try an email to Extreme with details, and see what they can offer. The belts were added and desired for the very reason you mention. That is to insulate the engine from load shock. I've operated combines with a CVT belt drive which did not slip. Go figure.

Warner makes multiple vbelt clutches, you will need to give them the torque and hp numbers you will be imputing before buying one. There is also another company call Extreme that makes quality electric clutches and they are much cheaper than Warner or Ogrua. There clutch pullyes are made out of billet aluminum and I have used them with good results. They also have a one year free replacement warranty. The mention of going with gear and chain drives I am opposed to. Anything that is going to be subjected to shock loads, belts are a lot more forgiving than chains and gears. I wouldnt worry about belts slipping, stump grinders and straw blowers use belts all the time. Better to slip a belt than break a chain.

 

[muddstopper]

I dont know if this number is still good, but Warner 815 389 3771. I talked to them about a electric clutch to pull a large water pump once. They spec'ed it out and it lasted for probably 10 years before it finally burnt out. I think the engineer I talked to was named Dave, but he has probably retired by now. I have the number to extreme somewhere. I found them very helpful and have bought 2 clutches from them. Again, its been a while. I did have a warrenty issue on one clutch, I called them up and they found when I bought the clutch and said it was fully covered and mailed me out a new one, I had it in a few days. still running it on my zero turn.

 

[ArlyA]

Does anyone have suggestions for shaft sizes??

The jack shaft I was thinking that 1.250 which largely matches the engines output shaft. Could we go smaller? The tiller is much tougher for me to guess. I'll include some photos of a one built in Italy but its a more narrow version, like just 3ft wide. Maybe 1.5 or 1, 5/8 mild steel for this one?

 

[ericm979]

With the tines solid mounted I'd think that bending strength if it hits something would be a concern.
Maybe a larger diameter tube instead of solid rod, for more bending strength without more weight?

Are you using a two stroke engine or was that just a stock pic?

 

[ArlyA]

Not a 2 stroke. We'll use either a B&S or Kohler V-twin that's about 37hp which are 4 strokes. Manufacturers of the large tiller do indeed use a structural tubing for the shaft but us simple guys working in a amateur shop, need to keep it simple, stupid. I'll attach a photo of a manufactured one.

Seems that a 1.5 shaft could do lots of smacking against rocks n stumps and not stay bent??

With the tines solid mounted I'd think that bending strength if it hits something would be a concern.
Maybe a larger diameter tube instead of solid rod, for more bending strength without more weight?

Are you using a two stroke engine or was that just a stock pic?