Square Drives - good, bad , and the ugly.
- Thread starter TimD
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First volley... ;D
I use square drive because i believe a properly set up system has less drag than a flex hex system. With a square drive the thrust load is taken at the strut. The flex cable is only in torque. With a collet setup the cable is being pushed on so bares hard against the side of the stuffing tube. The more thrust the prop produces the more it bares on the stuffing tube.
Also with a flex hex the engine is pushed forward in the rubber mounts by the prop. This is the main reason you have to set a gap between the strut and the drive dog. Yes the cable does contract a little under torque as well. In rough water the motor hammers back and forth as the prop loads and unloads. That is why people often have problems with there pipes getting longer, or throttle stops braeking off in carbs. The engine moves! This is one of the major reasons that many of the current engines have carbs with no throttle stops....
Some people say the bearing life of the engine is shorter with a flex hex. I have never noticed this myself.
The problem with square drive is getting a good system. I personally dont like taking the thrust load on teflon or whatever washers. No matter how slippery they are, the greater the thrust load the more friction there is! I only use ball thrust bearings, and it took me a while to find the right ones. Now I get at least a season out of them.
Also you need a ferrule system. I personally have not had problems using the black 8/32 grub screws in flex hexes. I use 243 Loctite on them. I have never stripped one or lost one since using the loctite.
Another system is the screwed in ferrule. I have not used this myself, but it eliminates the the grub screws. It is not very convenient on a mono tho, you need to get spanners between the tabs. I dont use this system because I cant thread my shafts.
Okay, I have said enough. 8)
Ian.
I use square drive because i believe a properly set up system has less drag than a flex hex system. With a square drive the thrust load is taken at the strut. The flex cable is only in torque. With a collet setup the cable is being pushed on so bares hard against the side of the stuffing tube. The more thrust the prop produces the more it bares on the stuffing tube.
Also with a flex hex the engine is pushed forward in the rubber mounts by the prop. This is the main reason you have to set a gap between the strut and the drive dog. Yes the cable does contract a little under torque as well. In rough water the motor hammers back and forth as the prop loads and unloads. That is why people often have problems with there pipes getting longer, or throttle stops braeking off in carbs. The engine moves! This is one of the major reasons that many of the current engines have carbs with no throttle stops....
Some people say the bearing life of the engine is shorter with a flex hex. I have never noticed this myself.
The problem with square drive is getting a good system. I personally dont like taking the thrust load on teflon or whatever washers. No matter how slippery they are, the greater the thrust load the more friction there is! I only use ball thrust bearings, and it took me a while to find the right ones. Now I get at least a season out of them.
Also you need a ferrule system. I personally have not had problems using the black 8/32 grub screws in flex hexes. I use 243 Loctite on them. I have never stripped one or lost one since using the loctite.
Another system is the screwed in ferrule. I have not used this myself, but it eliminates the the grub screws. It is not very convenient on a mono tho, you need to get spanners between the tabs. I dont use this system because I cant thread my shafts.
Okay, I have said enough. 8)
Ian.
EatMyShortsRacing
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Tabs??? What tabs???
Oh I forgot.... some mono owners have tabs.... ;D
I agree about square drive being the best way. I HATE LOSING PROPS!!!! Also the least amount of drag in the driveline... has to be faster.
EMS Racing The older I get the faster I was....
Oh I forgot.... some mono owners have tabs.... ;D
I agree about square drive being the best way. I HATE LOSING PROPS!!!! Also the least amount of drag in the driveline... has to be faster.
EMS Racing The older I get the faster I was....
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Craig,
Personally I think square drive is the ONLY way to go with the A-90's considering the bearing/crankshaft arrangement. However Seaducers are one of the more difficult boats to set up with square drive due to the very low strut settings required.
Dale,
You are correct about the grease, i forgot about that! On a hydro it quickly gets mostly washed off by water. In the configuration I run on the mono the grease gets trapped in that tunnel in front of the strut, so it doesn't get out onto the transom. I spray it with degreaser and hose it out from time to time... ;D
TimD,
Look at the pics of my mono with the large hole in front of the strut. I loosen the grub screws, remove the prop shaft, then push the ferrule up and to the left, then slide it out the back. I grease it up, and use a torch to illuminate the hole so I can push it back in. Probably a little more finicky than a flex hex. On a rigger it is much easier as the end of the stuffing tube is exposed, but with the centre sponson it would be like that on a mono.
The trick with the grub screws is to use the longer type so that the socket is a good length. Stainless ones are too soft and will strip out the socket. Good allen keys are essential, I have a collection that size. I used to stand my riggers on their front up against a wall so that the ferrule and grub screws are easy to get to.
By the way you dont need to remove the flex if you need to take the engine out. Just take out the engine mount screws and slide it forward until it comes off the end of the flex. Easy! 8)
No, the torque reaction is still taken by the engine mounts, after all the engine is generating the torque and the prop is absorbing it. But the thrust is no longer taken by the engine, it is taken at the strut. As a downside of square drive you need to ensure the strut is well clamped. The single bolt strut setup you have would not be adequate. All my boats 45 and larger have two bolts to hold the strut.
Consider one last thing. A ball thrust bearing is DESIGNED to take axial thrust. The front (small) bearing of an engine (which is the one that takes the load from the flex hex) is designed to take radial loads. The axial load capacity of deep groove bearings is a fraction of the radial capacity.......
Ian.
Personally I think square drive is the ONLY way to go with the A-90's considering the bearing/crankshaft arrangement. However Seaducers are one of the more difficult boats to set up with square drive due to the very low strut settings required.
Dale,
You are correct about the grease, i forgot about that! On a hydro it quickly gets mostly washed off by water. In the configuration I run on the mono the grease gets trapped in that tunnel in front of the strut, so it doesn't get out onto the transom. I spray it with degreaser and hose it out from time to time... ;D
TimD,
Look at the pics of my mono with the large hole in front of the strut. I loosen the grub screws, remove the prop shaft, then push the ferrule up and to the left, then slide it out the back. I grease it up, and use a torch to illuminate the hole so I can push it back in. Probably a little more finicky than a flex hex. On a rigger it is much easier as the end of the stuffing tube is exposed, but with the centre sponson it would be like that on a mono.
The trick with the grub screws is to use the longer type so that the socket is a good length. Stainless ones are too soft and will strip out the socket. Good allen keys are essential, I have a collection that size. I used to stand my riggers on their front up against a wall so that the ferrule and grub screws are easy to get to.
By the way you dont need to remove the flex if you need to take the engine out. Just take out the engine mount screws and slide it forward until it comes off the end of the flex. Easy! 8)
No, the torque reaction is still taken by the engine mounts, after all the engine is generating the torque and the prop is absorbing it. But the thrust is no longer taken by the engine, it is taken at the strut. As a downside of square drive you need to ensure the strut is well clamped. The single bolt strut setup you have would not be adequate. All my boats 45 and larger have two bolts to hold the strut.
Consider one last thing. A ball thrust bearing is DESIGNED to take axial thrust. The front (small) bearing of an engine (which is the one that takes the load from the flex hex) is designed to take radial loads. The axial load capacity of deep groove bearings is a fraction of the radial capacity.......
Ian.
Tim
i use squar drive with the threded ferels its not that hard to thred the shaft. The way that i do it is to first partially turn the threds on a lathe and then clean up with a die nut to finsh the threds this works well.
As far as the greas washing off you got to be kidding what a mess to clean up especially on the twin.
Ozzy
i use squar drive with the threded ferels its not that hard to thred the shaft. The way that i do it is to first partially turn the threds on a lathe and then clean up with a die nut to finsh the threds this works well.
As far as the greas washing off you got to be kidding what a mess to clean up especially on the twin.
Ozzy
Propjockey
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What about polishing the INSIDE of the stuffing tube? Maybe with one of those big, long pipe cleaners from the craft store and some Brasso (or any metal polish)?
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Paul,
Most of the grease washes off my boats! Maybe try putting less grease on your shafts! Most of it is pumped out on the starting stand before it hits the water anyway.... If you use teflon shaft liners you still need grease, but you dont need much! ;D
Prop Jockey,
The shaft will polish the inside of the stuffing tube.... ;D
Ian.
Most of the grease washes off my boats! Maybe try putting less grease on your shafts! Most of it is pumped out on the starting stand before it hits the water anyway.... If you use teflon shaft liners you still need grease, but you dont need much! ;D
Prop Jockey,
The shaft will polish the inside of the stuffing tube.... ;D
Ian.
EatMyShortsRacing
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well I still have the collet stuff on the Seaducers but I will be looking to change that. Maybe the 21 can stay.
I got one of the Tony Grinter threaded Ferrule/shaft combinations and they look pretty good. May try to retrofit that to the Seaducer.
so who has 3/16 square ended cables??? I need some.
EMS Racing On your marks, get set, sleep.
I got one of the Tony Grinter threaded Ferrule/shaft combinations and they look pretty good. May try to retrofit that to the Seaducer.
so who has 3/16 square ended cables??? I need some.
EMS Racing On your marks, get set, sleep.
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Craig,
The locally built seaducers with square drive had to have a step turned on the ferrules to give clearance to the bottom of the hull.
For the engine get the Aeromarine square drive to suit Picco, it will go straight on with the M8 stud.
Octura supply 3/16" square end cables, and also make a really good square drive collet to suit which fits on most 21's and 45's.
Nitrocrazed racing: Winning isn't everything......but losing isn't anything!!
The locally built seaducers with square drive had to have a step turned on the ferrules to give clearance to the bottom of the hull.
For the engine get the Aeromarine square drive to suit Picco, it will go straight on with the M8 stud.
Octura supply 3/16" square end cables, and also make a really good square drive collet to suit which fits on most 21's and 45's.
Nitrocrazed racing: Winning isn't everything......but losing isn't anything!!
