Toothed pulley sources

[Beakster]

Hi,

Any idea where I would find a toothed pulley to bolt to my helm wheel which I can then drive from a motor?  Also what size should I be looking for?

The largest I've found is this 190mm one 
Belt Drive Driving Sprocket Kit for 2 Stroke 66cc 80CC Engine Motorized Bicycle https://a.co/d/5EGOh96

It looks to me as if the commerical autopilot kits are using a pulley that's about 300mm.

Thanks

[seandepagnier]

It is possible to 3d print one, however my printer maxed out at 280mm and was slightly eccentric. I used hdt5m type belt.

[Sully]

I'm also struggling to find the correct gear for a wheel drive.

Pulleys are not as available as I thought. Apart from those you found in AliExpress, I found these. I still have doubts if this would be optimal for our purpose, as long as:

1) They would attach directly to the wheel shaft, in contrast to the use of J anchor bolts to the wheel spokes in other mountings (like CPT autopilot, Raymarine, etc...).

2) Their diameter is much smaller than those other J bolts mountings (16 cm vs 30 cm?).

On the other hand, following Sean advice, 3D printing may be the best option. I found some designs online (e.g. https://www.thingiverse.com/thing:5492156, https://www.thingiverse.com/thing:3636189), but no one adapts 100% to what I need and I don't have a printer nor knowledge on design. 

There is a thread in this forum where Sean posted his designs: https://forum.openmarine.net/showthread.php?tid=4342 and https://drive.google.com/drive/folders/1...BwMoeFjrUV. So I will probably try this and see what happens.

[Sully]

Anyone knows if it would be possible to make a disc of wood or any other material and to glue a htd5m belt on the outside, to be geared with another htd5m belt looking "inward"? In order to make it easy to build a toothed pulley.

[seandepagnier]

Anyone knows if it would be possible to make a disc of wood or any other material and to glue a htd5m belt on the outside, to be geared with another htd5m belt looking "inward"? In order to make it easy to build a toothed pulley.

Not sure if the profile is identical, but maybe..  not sure what glue you would use?

Another idea...  what if you make it out of wood and use small 3d printed sections for the toothed part?

[SVHM]

What about using an automotive serpentine belt with a tensioner and an idler as the motor side pulley? You could possibly even use the air conditioner pump clutch if you can adapt it to the wheel.

The tensioner should be able to keep the belt from slipping. An air conditioning pump has a lot of resistance when running and those belts work all day for years in hot places.

[seandepagnier]

Non-toothed belts require a lot more tension.. otherwise potentially it can work.

The typical wheel drives are designed differently so that if the large pulley is not perfectly aligned to the wheel it still works without affecting tension as there is a pin on the pedestal that prevents the whole apparatus from spinning on the wheel that can slide back in forth in a slot (as alignment changes)

This design is unfortunately more complex and has a bit of friction even when disengaged so not perfect, but something to consider as they assumed most people are not really capable of aligning the large pulley on the wheel. In this case the tooth size if say 5mm, the alignment of the pulley would need to be < 1mm.

What I am saying is that I think a 3d printed pulley is probably a good solution, you need to be careful to align it very perfectly.

[MacKludger]

fwiw, I have the 2 stroke bike kit from the first post installed on my boat. I haven't used it offshore in heavy seas, but in the bay it works very well. I think it's a 4:1 ratio, and I have it on a wiper motor. If doing it fresh, I might opt for a power steering motor to get extra torque. I first tried a tension pulley approach using the roller supplied with the kit, but I found it difficult to get working as I wanted. I opted for a "hinged box" design instead with a bolt latch, and it suits my needs. As a note, I did have to order a different diameter of hdt5m belt to fit my wheel pedestal installation. The small gear on the wiper motor is secured with a nut, JB Weld, and a set pin through the axle.

Short clip of me waggling the IMU at the dock:
https://www.youtube.com/shorts/7anuzTAU0g8

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One other thought that I tried with limited success: you could try laying a belt teeth-in inside of a styrofoam mold with a circular cutout, then fill the interior with thickened epoxy or poly resin to "cast" a gear.