Volvo folding props on Yanmar saildrive? Can they be resplined?

Hello. My new sailing cat fitted with 3GM30s and SD20 saildrives had some dismantled volvo 3 blade folders on board. So I done them all up ready to fit to the boat on the haulout and they seemed very loose on the splines so I had to reuse the fixed 3 blade props.

The odd thing is, if they don't fit why were they on the boat?

Is it possible that the splines are flogged out? They slide on OK but the play seems excessive to me. I could really rock them around and they slid back far enough to hit the zincs on the sail drives.

I want folders on this boat and they cost around $6,000 to replace. So I wonder if I can get them to work? I have been told they should fit.

Any suggestions on what is going on?

Also, the folders are left and right, and the fixed props are both left. But as far as I am aware its no prob to reverse the direction on a SD20?

 

I have no doubt whatsoever, that you can source new props for a hellava lot less than $6000. Dont be afraid to buy from overseas...

This was one of the first sites i googled... http://shop.rkmarine.co.uk/sections/88/2_blade_folding_props/

 

Cheers. If I buy new it will certainly be from overseas! Mine are 3 blades, which would cost a fair bit more. But if possible I would use 2 blades. My preference is flexofold. I am waiting on a price back for them just to see. I would then get them from the USA by a connection with discounts.

Either way, if I can just get the ones I already have to work it would be the best solution.

I would love to hear peoples opinions on why they are so loose. If its because the spines are worn, or if they are probably just the wrong size to begin with? I was led to believe with spines in general, when they get bigger they increase the spline count rather than just make the same number of splines bigger.

 

As a fair to good amateur machinist with the ability to machine both internal and external splines, allow me to say that your question is unanswerable with the currently provided information.

They could be worn loose or they could be the wrong size.

The only way to know for sure is to get the manufacturer specs on the splines and then measure both the shafts and the prop hubs to see if they are within specification.

For a less precise answer (but possible useable) you need to accurately measure everything and then post the information here, with detailed pictures, or get a machinist to take a personal look.

And by accurate measurements, I mean using a micrometer capable of reading to 0.0001" resolution so you get answere good to better than 0.001". A ruler or even a set of verniers doesn't really cut it.

Doing anything else, particularly on an internet forum, is simply intellectual wanking and a waste of time. There are *pages* of specifications on splines and their fits in Machinerys Handbook etc, and *none* of them prevent a manufacturer from inventing their own proprietary one.

PDW

 

PDW, that super accurate measurement will certainly be required if I want to get new splines custom made to suit my saildrive shafts, and the machinist does not know the shaft specs, which possibly they would if they specialise in prop work and are familiar with my prob. The boat is back in the water now so I can not take any accurate measurements. I do have the folding props though.

I was merely hoping some general information could be given by people experienced in these matters such as volvo and yanmar spline sizing and if they are supposed to be the same. This problem might have been well known, so it was worth asking.

I have been told by a few sources now that they should indeed be the same size 17 spline, 28mm shaft, which leads me to believe there may be a ware issue in the volvo hubs. The fixed props fit well and the shaft splines do not appear to be worn. I will try to contact volvo next week to confirm.

I would gladly take them in to get them looked at. I am in Brisbane and if anyone can reccomend anyone I would like to talk to them. The fixed props that went back on look pretty much the same as an outboard motor prop with a rubber donut and a metal spline. But the volvo setup is a little different, but I hoped they could be resplined somehow in a similar way.

 

re props

Hi Dennis
http://www.solas.com.au/kiwi-prop/ Maybe these people can help

 

Pity you're not down here as I'd happily take a look at them for you.

If you can take some decent close-up photos of the prop splines then something might be obvious, don't know.

I had to machine up a spacer/adaptor for a friend's saildrive a couple years ago - don't remember anything obviously non-standard about the spline setup.

Where is the free play? Are the props a loose fit on the shaft - this would indicate that the minor diameter of the hub spline is too big and the major diameter is also. This is what I mean about different standards - both might be 28mm OD shafts and the shafts might have 17 splines, but one could be an involute spline form and the other straight sided, plus the splines could be cut to different depths.

If the props fit on the shafts well but have excess rotary motion, I'd say it was spline wear but it still could be a mismatch of spline profile.

Given the price of folding/feathering props it's certainly worth a bit of your time trying to sort it out.

PDW

 

Thanks PDW, yes the costs involved are huge which is why I would love to sort it out. The there is play in all directions. I can rotate it back and forward a little, but the major issue is I can rock them back and forth, which means that once tight they may not be running true and this would cause a major balance issue.

One hub certainly does have a visible issue where part of the splines are missing in a certain area, but the prob appears to be in a small enough area that it should not make that much of a big deal. But the fact this damage is there points to there possibly being more worn than just this obvious area.

I will try to get some pics when I get home, but as you can imagine it will be hard to take pics of an internal spine.

 

You need only two simple measurements to give a machinists: diameter and number of splines.

 

Oh absolutely. That explains why there are over 35 pages of very small print, densely packed, in the 22nd edition of Machinerys Handbook, all dealing with splines and their sizes/fits. As I have already said, there are 2 different forms of spline in common use, involute splines and straight splines.

Can you tell me just how many splines you have either personally machined, or paid a machinist to make for you, giving him nothing except a diameter and spline count (IOW no sample to match)? Because I'm very much of the opinion that the answer is a nice round number......

PDW

 

There are 3 axes of movement.

Nice sliding fit but fore & aft on the splined shaft - ie end float. This just needs a spacer/bushing of the appropriate size. I've done this for a friend of mine to take out the end float in his saildrive. Dead simple job.

Next, a nice sliding fit of the hub on the shaft, but considerable rotary play/backlash. This is likely to be wear but might be a spline size mismatch. Hard to tell without looking at the things in situ.

Last is a cocking movement for want of a better term. Indicates that the outside diameter of the hub is too large as is the inside diameter. If this is the case, same as above, hard to tell wear from a mis-fit but I'd be more inclined to suspect the latter.

Given that most boats spend 90% or more of their time in forward I'd look closely at the hub spline profiles. Does one side of the spline look markedly different from the other? If so, I'd say they had significant wear.

Question comes down to, how much time & money do you want to spend in pursuit of this? My Autostream prop was serious dollars so I expect you're looking at $7K for a pair of props.....

PDW

 

I haven't kept count of the splines
The OP is asking about splines on a propeller, so they are not some weird size or design. They will be evenly spaced so he only needs to know the diameter and number of splines. Further, the splined hubs that are pressed in the propellers are standard, so he only needs to choose from the commercially available models. It should be a 17 spline 28mm shaft. You can get new folding propellers for L250-340 in the UK.
http://www.sillette.co.uk/pdf/sillette_marine_propulsion_catalogue.pdf