The Steamboating Forum

Hi Malcolm

Whilst I cannot offer anything like the technical expertise of the learned members whose posts fill this topic, but I can offer a little of the 'learning by experience' bit.

For context, Frances Ann has a shortish propeller shaft with one pillow block/thrust block bearing, then a pair of 3/8 chains connecting the drive to a lay shaft that runs all the way down the bilges under the cockpit (3 pillow blocks). A second pair of chains then picks up the drive from the engine.

The lack of space meant that the prop shaft was almost at the level of the cabin floor, so that the latter had to be either raised or have a 'hump' in it. So my advice would be not to busily build you cabin and then think about the shaft. Make it iterative as setting the cabin floor height decides the height of any seating, assuming that you want non 'boat mad' family members to join you and feel comfortable.

That same lack of space meant that I could not get toothed belt pulleys small enough to fit in the space. That pushed me to chain as there were very small sprockets available. However, I did not read the Reynolds Chain guidance booklet and so failed to realise that a chain tensioner would be a must. That was only found out when there was finally steam at the engine and some power was put on the system! Not sure if they are needed for toothed belts, but if space precludes the latter and you end up with chain, don't fall into my trap.

Regards

Pete

Toothed belt drives can be constructed w/o a tensioner, but very precise control of the center-center distance is required. Piloted flange bearings in a steel frame w/ bored holes works from personal experience. Of course, if the center-to-center distance is adjustable, no issues arise.

- Bart

I have somewhat skimmed this thread, but the steam narrowboat 'whistle down the wind' uses a belt between the shaft to the engine and the propeller shaft, in order to speed the prop up by around 1:2 after the original gearbox based solution failed a number of times even after improvements to the boxes internals where made in the process of fixing it.

My universities 'formula student' car also used a surprisingly slightly toothed belt as the final drive solution, it was a light car, but had a quite significant bike engine powering it and was not afraid of doing an aggressive launch off the line with sticky rubber fitted.

So I certainly have to doubt that such a belt can do it, as obviously I am quite sure and appropriately specified v-belt or poly-v could also do.]

Depending on the size of the flywheel etc, the thing that will kill it is the shock loadings. A larger flywheel reduces the need for the propeller to act as a flywheel in smoothing out the power strokes, but also increased the shock should something become wedged solidly in the prop which then has to stop the flywheel as well as the engine. That said, if its a really high load, maybe you want to belt as a weak link!

Daniel

Some motor cycles were produced with toothed belt final drives instead of chains. Don't think the idea caught on too well, as I don't think any still are.

Mike Rometer wrote:Some motor cycles were produced with toothed belt final drives instead of chains. Don't think the idea caught on too well, as I don't think any still are.

This is still available on bikes by several different manufacturers.... the belt drives work well on street bikes and they are low maintenance and quiet. They're not considered suitable for bikes used off-road due to potential damage caused by catching a rock between the belt and the pulley.

- Bart

Guys even more good advice! I will bear all this in mind as we iterate towards a final solution - one thing in my favour is that the Cabin is at the other end of the boat to the engine/drive arrangements, so WRT what PeteThePen1 said

So my advice would be not to busily build you cabin and then think about the shaft. Make it iterative as setting the cabin floor height decides the height of any seating, assuming that you want non 'boat mad' family members to join you and feel comfortable.

I think I can seperate the two issues - the first item to be addressed was how to ensure that the engine/boiler did not encroach on the Cabin/head/bunks etc.! I'll post some pics of current plans on the Blog http://sy-befur.co.ukin the next day to give you a feel for where I am at...

thanks again everyone.

Mal

Mike Rometer wrote:Some motor cycles were produced with toothed belt final drives instead of chains. Don't think the idea caught on too well, as I don't think any still are.

All newer Harley Davidsons are Belt Drive. I have several and never a belt problem.

"All newer Harley Davidsons are Belt Drive. I have several and never a belt problem."

At the races a few years ago there was always a chasis dynometer where anyone could pay $20 and get a RWHP vs RPM output for their cycle. I have withessed several runs on this machinery, and the highest power I ever saw on a 1340cc Harley was 52 horsepower. My wife's Honda 900RR (829cc) made 117 horsepower on the same dynometer.

The toothed belt drives have many good features, but still do not come close to the power transmission capability of roller chain drive. All sport bikes use roller chain drive.

Ah but the difference between the H-D and the Honda begins a long way before the belt drive

Which one makes more torque at 1000 rpm?