Carsten,
You suggested this very good thread from boatdesign.net:
>>https://www.boatdesign.net/threads/smaller-vessel-thrust-bearings.46072/
In that comment Mike Johns said this:
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It would be nice to find a commercial bearing housing for two
tapered roller bearings and seals. But there are only the high
end marketed products mentioned before and they are
probably not much better than the spherical roller bearing.
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Seems to me Mike Johns is implying a housing with two tapered roller bearings would be what he would like to use. ZF uses tapered roller bearings in their small boat transmissions (e.g. ZF 25).
Question:
Isn't the trailer hub a housing for two tapered roller bearings and seals?
I tried to track down Mike Johns to ask him if he had thoughts about a trailer hub like this. No luck though. He has not been on the boatdsesign list since last year. But holding the hub in my hands it seems like a quite robust bit of gear. Easily as robust as the Walter V-drive my boat came with. However I do wish the bearings in the hub were the same size and the shaft to fit them could be more like 30 or 35mm. It could with a larger hub but then you have to start with an even larger blank for the shaft.
Also, an issue with any of these bearings is a housing to keep the lubricant in. What do you think of a sealed bearing in this application? Are there sealed versions of the spherical roller bearing you like? I can't find any and I would suspect no because a seal would not be conducive to the spherical motion of the bearing. So then a housing is need with seals. And to handle all those torsion forces and misalignments you speak of what sort of seals would be needed?
Here is a sealed double roller angular contact ball bearing:
https://intechbearing.com/products/5207-2rs-2-row-angular-contact-ball-bearing
https://www.kugellager-express.de/angular-ball-bearing-5207-2rs-tn-3207-2rs-tn-35x72x27-mm
This is of the same type used in my Walter v-drive for the thrust bearing but larger and in a sealed version. It should be more than adequate for the load (as the smaller one in the v-drive has been for 43 years). Would this be a possible choice if a suitable housing could be found or made? The bearing is rated for 6000 rpm and would see no more than 1000 in a small boat application so that seems like light duty for RPM.
For these very nice bearings that Egbert found, how are they retained in the housing? It looks like just a press fit with no shoulder on either side and I don't see any set screws on the housing (just on the bearing to hold to the shaft). So what transfers the axial load to the housing? The bearing may be rated for the load but the load has to be transferred to the housing somehow? I also see these housings in a 3-bolt of 4-bolt flange which might be a more robust choice. Also is stainless as pointless as that may be.
https://www.kugellager-express.de/all-flange-bearing-housing-units
Thanks,
Dan Pfeiffer
Thanks for the housing link, Egbert !I still would go for a double spherical roller bearing solution (not a ball bearing), as it is much more flexible to absorb torsion forces and misalignments, so no trailer hub solution for me.Personally, I should also consider the life span of the system when converting my saildrive, or change to shaft drive.I'm not young, and my sailing days may be limited to 5-15 years, knock, knock, knock.(My back hurts today, ouch...)So, boat value is an issue.I don't want to save 300$ now, just to devaluate my boat with 3000$.I want to make a bullet proof design, that can convince a buyer too.If it is just you that will sail the boat until it (or you) is scrapped, then no problem. Then anything goes.But when selling in a good manner, it is why a good overall mechanically reliable design, and a good labelling of voltages and cable arrangements becomes important.A transparent and easily understood system layout convinces a buyer, that the DIY conversion has been done with care and mind. Let that be a document following the boat or a throughout good labelling (or both).In hope of your understanding of my poor english...Cheers, guysCarstenOn Thursday, 1 April 2021, 01:13:16 GMT+8, Egbert Van popta <motorstunter@gmail.com> wrote:I looked at the specs of the ucfl bearing at the skf site and did the math. The axial load range is more than sufficient for my 12kw motor. Radial load 15kn of which 20% can be used as axial load force. It's not a huge margin, but as it is a very cheap and easy to change bearing I'm happy with that. On this site they weirdly enough don't mention the 20% axial load , but they give tips to increase the axial load capability.On the end of this written piece they link to plummer block housings with spherical bearings. Isn't this what you are looking for?Egbert
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