Re: Ang.:Re: [electricboats] Sizing motor for 45-50’ boats

Dan,

I have reviewed your drawings. Very interesting, a hybrid boat !

When you are using a toothbelt drive, you actually don't need a Drivesaver, as the toothbelt will slip or break in a crash-stop situation. A new belt is far easier (and cheaper) to replace than a Drivesaver coupling.

The inertia in an electric motor (the rotating mass) is far less than by a diesel engine with a big flywheel, and you have no gearbox anymore to worry about.

The position of the ME1616 motor is almost free to choose, meaning that you can add a pulley to the shaft almost anywhere until you reach the sterndrive. The distance from shaft centerline to motor centerline is also only determined of the toothbelt length. You don't HAVE to place it in one common frameplate.

If you make the motor base adjustable, it is easy to change the belt.

If you make the frameplate with fixed driveshaft and motor shaft, like on your drawing, you likely will add an adjustable bearing roller to adjust the tension of the belt (same like in a car engine, for a camshaft toothbelt). Very handy too, for changes of pulleys for reduction ratio. (The roller must roll on the flat side of the belt, of course.)

I guess a complete roller kit for a car is rather inexpensive.

Why use aluminum for the construction?

I know that it easier to cut a thread and drill a hole in aluminum than in steel.

But :

Steel channels and steel plates are much easier to repair if you make a mistake, or something should be re-positioned.

Aluminum welding is no fun, and threads cut in steel are much stronger. You use Helicoils in aluminium constructions, if threads shall be strong and lasting. That requires special tools, so - not for a DIY mechanic.

If you need something done, any workshop in any port can weld steel, and can always find a standard machine tap in the dirty drawers.

I would say, that an ME1616 used as a generator might be shooting sparrows with a cannon - an expensive solution. Balmar have some 48V alternators, you can check them out.

How is your plan for cooling of the ME1616 for the shaft ? (I assume that you will make a common system for the Kubota and the ME1616.)

What kind of battery bank is in your plans ?

Do you have a photo of the shaft and of the engine room, as it is now ?

Cheers,

Carsten

On Thursday, 18 March 2021, 01:50:03 GMT+8, Dan Pfeiffer <dan@pfeiffer.net> wrote:

Carsten,

Can you elaborate?  What kind of steel would you recommend for the short shaft on the reduction gear?  And you thin the SS hub is not worth the added expense?  I can certainly paint all this stuff. 


Attached is sketch of one version of my reduction gear.  I am still refining it.  This version is made from an aluminum c-channel (from Online Metals).  I will probably change the c-channel for a flat plate because I'll have more flexibility in the choice of pulleys and that will let me better fine tune the reduction ratio.  I also have a variable pitch prop to play with.  The drive will tilt back about 15 deg in the boat.  This version shows a DriveSaver  between the shaft couplings.  I have not worked all that out yet.  I may do a soft mount between the drive assembly and the beds. 

I have the motor mounted to the side to free up space in the compartment for a genset.  I have a nice new Kubota D722 and am exploring fitting another ME1616 to it to make a DC genset.  It should all fit in the compartment.  The Kubota is remarkably compact.   Wth the ME1616 I should be able to get 8kW? I chose the ME1616 for it's water cooling which I think will bne important at 8kW.   The BLDC motor with a rectifier and regulator could get into the 93% efficiancy range.  Or so I am told.     I am still researching that.   For now my attention is on the drive line. 



To Steve's questions,

I think the thrust from the prop is on the order of 1000lbs.  There was a recent post with some tests of that using a spring scale.  I just doubled that to spec my parts.  There are several larger hub options too.  For your setup (as I understand it) I would proably want to go bigger.  Like a 6-bolt hub like this:
https://www.etrailer.com/Trailer-Hubs-and-Drums/Kodiak/KH42655S.html
But I don't know the details of your system and I am not an engineer.  Just a hobbyist. 


The threaded portion on my shaft is very short.  Just enough to tighten the threaded collar against the bushing and bearing.  Forward of that is the section the drive pullet will attach to.  That's 1" diameter for the bushing that the pulley mounts with.   I have not yet determined all the final lengths for the different sections of trhe shaft.  I need to get some more measurements on the boat. 

For tension of the belt I think you would need idlers on both sides and they would have to be quite beefy.  The drive needs to run in both directions.  Look at the belt arrangement on the Beta Parallel Hybrid Motors. 
http://betamarine.co.uk/wp-content/uploads/2020/07/B115T_HE_Twin_Hybrid-1024x1024.jpg

I think something like that would work.  It's more parts but it might make things easier in some respects?    R = 1/P where R is reliability and P is the number of parts.   


Dan Pfeiffer

 

On 2021-03-16 12:28 pm, Carsten via groups.io wrote:

 

Thanks, Dan !

 

Save your money on stainless (exept the shaft part from cutless bearing to prop).

You have an inboard, and mechanical properties of good ol "rusty" steel are usually better than ss.

 

Could you please provide a sketch of your setup ?

It seems very interesting !

 

Carsten

 

 

On Tuesday, 16 March 2021, 23:54:19 GMT+8, Dan Pfeiffer <dan@pfeiffer.net> wrote:

 

 

(sorry if this is a repeat - I posted it 8hrs ago and it never showed up)

I have also spent a lot of time looking for thrust bearing options.  That Python Drive looks like a great solution where there is room to fit it.  Looks like it will leave some room in the wallet too. 

Thunderstruck uses a trailer hub with tapered roller bearings.  It's a good simple and inexpensive solution for small setups (<30hp?).   I think this is the hub they use:

https://www.agrisupply.com/trailer-hub-capacity/p/25669/?sid=asf10&eid=Easf10&zmam=77232640&zmas=1&zmac=1&zmap=25669&eid=gl020116&sid=google&gclid=Cj0KCQiAyoeCBhCTARIsAOfpKxg-UWWx-rrzYMZA1hBZLyEhEjTr2oVK21ludtM8zMI49vR0KLRQ3D8aAgkUEALw_wcB

One issue with these is setting the pre-load on the bearings.  If you have changed the wheel bearings on a car you know what this is about.  Thunderstruck does it by using a fixed collar and bushing on the prop side of the bearing and another bushing on the other side that is held in place by the tapered bushing that holds the toothed belt for the reduction gear pulley.  It's a simple setup with only a few parts and some simple machining on the shaft.

I am fabricating my own belt drive reduction gear for my boat (12kW motor) and I am going to use a trailer hub that's one size larger and available in stainless steel (with a price premium of course).  This is what I am using:
https://www.etrailer.com/Trailer-Hubs-and-Drums/Kodiak/KH84545S.html

I am going to use a threaded split collar on the shaft to set the pre-load on the bearing.  My shaft will be a more complicated machining (including a threaded section) but I think it will be a better way to set and hold the pre-load on the bearings.   The two parts I have to make are the shaft and the bushing.  Both will be stainless steel.  The hub will remain stock with no machining.  The bearings are standard hub bearings you can get anywhere.   All the parts except the bearings will be stainless steel.  And the bearings will be in the grease.  The bushing will have the OD sized to fit the grease seal on the hub that takes the place of the standard cap when it is used on a wheel.  It's a standard grease seal but I had to hunt a bit to sort out fitting it in the hub. 

This could easily be scaled up for larger applications.   These hubs come in at least two larger sizes in stainless. 

The bearing, reduction gear assembly, and motor will mount to an aluminum plate similar to what Thunderstruck does.  I was going to use a piece of c-channel and that would work well but I wanted more flexibility in the pulley sizing to be better able to fine tune the reduction ratio and the c-channel limits the diameter of the gear pulley a bit.  I am still sorting that part out but I am aiming for about 3:1 for the reduction.  The world of timing belts and pulleys is vast and has been difficult to get a handle on so far. 


Dan Pfeiffer

 

On 2021-03-15 11:29 pm, Carsten via groups.io wrote:

Of course you'll need a double bearing for axial loads in forward and reverse...

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På tir., den 16. mar. 2021 klokken 10:47, Carsten via groups.io

<Carstensemail=yahoo.com@groups.io> skrev:

Hi, Steve

 

Consider to make your thrust bearing with a high quality spherical roller thrust bearing, eg. of SKF brand. This can accept torsional forces much better than ball thrust bearings.

Then you don't need the expensive solutions with a lot of rubber (which needs care and replacement when worn).

 

The tooth belt drive (not V-belt, which introduces higher radial forces to the shaft) can be mounted either before or after the thrust bearing.

The housing for the thrust bearing should best be mounted close to the cutlass bearing, to minimize torsional bending of a long shaft.

 

Could you please post some photos of your existing setup of the shaft and cutlass ?

 

Have you considered which prop you will use for your new setup ?

Going electric has a lot of torque at low revs, which is very useful during maneuvering, so the prop should have less pitch and larger diameter, imho.

 

Carsten

 

 

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På tir., den 16. mar. 2021 klokken 4:52, Steven Borg

<steve@theborg.family> skrev:

I'm in the process of planning and installing a Hyper-9 motor at 154V with a battery bank of 48 280Ah 3.2V LiFePO4 batteries I received from China. The motor is rated to be plenty powerful to replace my 100 HP Diesel (which has been removed).  I'll keep everyone posted when it's installed.

In the meantime, I have a related question (maybe for ChristopherH?) around thrust bearings.  I've decided to use a belt drive (like the photos above, but for a single motor and gear.  But without the transmission I had planned on using (with integrated thrust bearings), I'm going to need to anchor the propshaft to the boat.  

Christopher, what inline thrust bearing did you use?  I'm trying to determine if I should build out a thrust bearing somewhere along the prop shaft, or whether I should integrate the thrust bearing into the engine mount, either before or after the belt pulley driving the shaft.  Also, if there's a pre-made thrust bearing for boats, I can't seem to find them (except large ones for giant ships). Does anyone know what they'd be called, so I can search for them.  (Yes, this is an embarrassing, totally newbie, question to ask, but I just can't seem to find them, so have been debating whether to just engineer my own from bearings off Granger or McMaster-Carr).

I'm not sure those questions even made sense, but that's where I'm starting...  Still trying to figure out the best way to get this done!  

This has been an amazing thread!  Thank you!