Sprockets, chain for Rotary Drive autopilot

[mlpayne]

I see on-going threads indicating folks are DIY installing Raymarine EV200 AP systems with rotary drive units. I installed a system on my H376 last winter. The bill of materials used for the sprockets, chain and chain tensioner are:

Sourced from Grainger:
TRITAN Sprocket,5.000in OD,0.375in PD,1inBD,#40 Item # 36GA58 Mfr. Model # 35BS40H X 1 Catalog Page # N/A UNSPSC # 31171901
TRITAN Sprocket,1.732inOD,0.375inPD,5/8inBD,#13 Item # 36GA23 Mfr. Model # 35BS13H X 5/8 Catalog Page # N/A UNSPSC # 31171901
Sourced from McMaster Carr
High-Strength Corrosion-Resistant Roller Chain, Single Strand, ANSI Number 35, 3/8" Pitch
Floating Roller Chain Tensioner for ANSI Number 35 Roller Chain

 

[scottdube]

I would love to see a picture of the chain tensioner set up if you have one. Mine does not have a tensioner but could use one I think.

 

[mlpayne]

it pretty much looks just like this

... provided a simple solution to getting the chain tight enough. attempting to link the chain together on the sprockets and take up enough slack to avoid slop just was not possible - that's what a tensioner is for anyway :>) MFR picture differs from reality in that the side straps are not bolted onto the blocks - they are zip locked much like the way cable ties work. so you put a block on either side of the chain, insert the straps and push together until desired tension achieved. quick and easy. added benefit is if the rotary drive ever failed (locked up preventing manual steering), the chain can be removed by simply cutting a strap and removing the tensioner.

 

[smokey73]

it pretty much looks just like thisView attachment 141854 ... provided a simple solution to getting the chain tight enough. attempting to link the chain together on the sprockets and take up enough slack to avoid slop just was not possible - that's what a tensioner is for anyway :>) MFR picture differs from reality in that the side straps are not bolted onto the blocks - they are zip locked much like the way cable ties work. so you put a block on either side of the chain, insert the straps and push together until desired tension achieved. quick and easy. added benefit is if the rotary drive ever failed (locked up preventing manual steering), the chain can be removed by simply cutting a strap and removing the tensioner.

Interesting? Is the tensioner Carbon Steel (Magnetic) and if so did the carbon steel sprockets and chain affect the magnetic compass? I like the idea of a tensioner. Are the blocks made of steel or some synthetic low friction material? It would seem that this might cause additional load/strain on the motor. Not a criticism of the set up, just questions for inquiring minds. My sprocket and chain are both stainless steel. Thanks for the info in advance.

 

[smokey73]

Looking at the tensioner it looks like if someone wanted to make one with a sprocket or even a nylon sheave in roller bearings it would be relatively easy to do, especially with the idea of using something like zip ties or similar to provide the tension. Just thinking outside the box if I want a stainless tensioner. I'll probably fiddle with a possible design.

 

[mlpayne]

Tensioner blocks are not metal; they are low friction and do not introduce a strain on the rotary drive. The sprockets / chain used did not affect the compass.

 

[mlpayne]

I suppose if one has the time and desire to fabricate a DIY tensioner of comparable spec - go for it. the material is plastic and the housing material is 304 stainless. At $47 the economics on this made sense to me.

 

[smokey73]

Wow - I found a really cool looking chain tensioner on line. Don't know if it will fit any of our applications but it probably will. I have ANSI 40 1/2 inch stainless steel chain. I have no idea of the price but it is a really interesting way to apply tension. I'll see if I can get a cost and let people know.

https://www.usarollerchain.com/RR500-34-Roll-Ring-Tensioner-p/rr500-34.htm

I like the idea of an this one.

 

[smokey73]

I suppose if one has the time and desire to fabricate a DIY tensioner of comparable spec - go for it. the material is plastic and the housing material is 304 stainless. At $47 the economics on this made sense to me.

Thanks for the reply. I looked up the tensioner and saw it was plastic but I didn't see the material for the housing. You are right, the economics do not justify fabricating one other than the challenge (which I have enough of). I was just concerned about mixing stainless and carbon but if its 304 that is perfect. I'm going to get one. I'll still check the price on the internal tensioner but I'd guess its about an order of magnitude more.

Thanks for the rapid reply