Multiple Gear Boat w/ Propeller

[Pedaler]

I have this idea, and I've googled around and searched this forum quite a bit. The concept of utilizing gears, like on a mountain bike seems to be left out in mostly every pedal-powered boat project.

I'm not in the market for the most speed and efficiency exactly, but I do want my boat to go considerably faster than by just rowing, so as not to defeat the purpose of the whole ordeal.

In short, from what I imagine it to look like right now. It is my old regular 18 speed mountain bike: http://www.teamkarim.com/bikes/used/images/080403-12.jpg,
with the front wheel taken off and the forks mounted on the middle of the floor of my flat bottom boat: http://i.ebayimg.com/23/!BT4FL-!Bmk~$(KGrHgoH-DwEjlLlzbOWBKKv85WMj!~~_1.JPG

Now from what I've learned in this forum by searching is that I will need some sort of right angle converter (don't know what it's called) like this: http://www.mitrpak.com/images/RA_UNIT.jpeg that will take the spinning motion of the back wheel and bend it 90 degrees so that it can be transferred through a metal rod on the end of which is a propeller.

I wish I could use the back wheel so that I could keep the inertia from it spinning after I stop pedaling, but I realize that that would make things quite a bit more complex.

I found that the idea is partially existant in a product called the Shuttle Bike: http://www.gizmag.com/go/2505/gallery/.

As I understand, the back wheel is disconnected from the gearbox and does not spin. The gears are capable of still being used on the water. The only thing that bothers me is why such a small, double-bladed propeller? If I can start out on first gear, I would be able to get the boat moving with a huge, thick, powerful propeller and switch gears on to increase speed.

For the information, I am on a tight budget, in the understanding that I don't intend to spend much money on the parts for this. I intend to salvage an old bicycle, use materials that I can find in mine or my buddies' garages and not impair my row boat's ability to swim normally again. I simply need the first push of guidance and outlay of how the project should be built.

[Guest625101138]

........ The only thing that bothers me is why such a small, double-bladed propeller? If I can start out on first gear, I would be able to get the boat moving with a huge, thick, powerful propeller and switch gears on to increase speed.

.....

Huge, thick, powerful propeller requires huge, heavy powerful engine to operate in its efficient range.

Even the most powerful humans cannot outperform a modern electric motor that weighs 150 grams plus a few kilograms of battery to power it. A small internal combustion engine around 500 grams and a few litres of fuel will also outperform any human.

To get the best from a human you want an efficient propeller and this will have the longest, thinnest blades that are capable of withstanding the small forces involved in most human powered boats.

If you are a world class athlete with very strong lower body and not highly developed upper body - say a sprint cyclist, you could get the boat to plane if you set everything up for maximum efficiency. In this case gears might offer some benefit as the boat will go through different operating regimes - from displacement to planing mode. A world class athlete could only sustain planing mode for a few seconds though.

Joe Average will not be able to get the boat to plane so is condemned to displacement mode and there is little value in having gears. There may be rare occasions when operating in strong head winds that you would like to use a lower gear if available. I doubt that you will operate that boat in the ocean where you need to contend with large swells that might afford some advantage to constantly changing gears.

Rick W

[Rangerspeedboat]

I have always wanted to use mountian bike gears on a go cart. On a boat works too.

I would get a smaller lighter boat, row with that you'll go fast and excersise.

When rowing your working your upper body, thats what you want to work on because that shows. If your going to pedal a bike have it on land so you can get some speed.

[Pedaler]

Hah, thanks for the advice Rangerspeedboat, but my whole purpose for this project is to use "the most powerful muscles of the body, the legs" to propel my boat. I'm not looking for the most efficiency as I know I lost that bet when deciding to use my flat bottom boat; and building muscles isn't really the goal here. I work out apart from this.

Rick, that's some knowledgeable...knowledge! I still don't quite understand however why gears wouldn't be so useful. Would it not work as it does in cars and bikes on the road? Start out with gear 1 to break the potential energy barrier, and then ease yourself into higher speeds by changing gears?
Check this video out: http://www.youtube.com/watch?v=vPCDFEbJWqU. At around 1:08, you can see the swedish boat with 2 pedalers who actually do plane. And their boat won the race. Though I'm not looking to plane on my boat, I do want maximum possible, (but reasonable) speed. I am confined to using just my Huffy Stone Mountain Cheap bike and the 10 or 12 foot flat bottom boat I have. I know, I know; it's not exactly the high end gear that you guys like using, it's more like redneck project utilizing garbage from the shed.

At any rate, the main part, the actual mounting of the bike and adapting the spinning power of either the gears or the wheel through to the rod which holds the propeller is the first and most important step. Then I would be able to experiment between propeller styles and sizes to see what fits me most.

I can sort of fathom how I would mount the bicycle, but the most difficult part for me at this point is the conversion of the actual power that comes out of the gearbox to the rod that spins and propels the propeller. Keep in mind that I need to be able to switch gears and the output of the functional "transmission" of the bicycle needs to be used to propel the boat. I'm even finding it hard to explain myself properly because of my lack of terminology in the subject matter.

[Guest625101138]

That boat is on foils. Foils are 2 to 3 times more efficient than a planing hull so require much less effort to fly. A planing surface is a very inefficient foil.

I am one of the few people who race pedal boats against other forms of human powered craft. My V11 design is the current 24 hour distance record holder. I have done considerable research and development to get the best from human power on water.

There is quite a lot of detail on this thread:
http://www.boatdesign.net/forums/boat-design/pedal-powered-boats-23345-20.html
The latest pictures are of V14.

Probably the best set up for your prop using a single gearbox would be a curved shaft off the transom unless you want to punch a hole in the bottom for a shaft tube. The later could be done with some nice engineering but I always try to avoid hull penetrations.

Rick W

[Pedaler]

So is there never a time when you're pedaling on your single-speed boat and you reach a certain RPM (or should I say pedal per minute) when you wished you could just switch to the next gear so that you wouldn't have to pedal so fast to go the same, or an even faster speed?

I guess I'm still confused about it because as I see it, when you're stuck with one gear on the boat, it's like being stuck on those older single speed bikes. It's about on gear 10 always, so you can't really go uphill on it, and if you're going on a straight road or downhill, you can't pedal any faster, but there is still room for speed because on a speed bike, you could go as far as gear 18 or 21.

And could you please elaborate a little more on the mechanism used to transfer the rotating motion from the gears all the way to the propeller.

[Guest625101138]

So is there never a time when you're pedaling on your single-speed boat and you reach a certain RPM (or should I say pedal per minute) when you wished you could just switch to the next gear so that you wouldn't have to pedal so fast to go the same, or an even faster speed?

I guess I'm still confused about it because as I see it, when you're stuck with one gear on the boat, it's like being stuck on those older single speed bikes. It's about on gear 10 always, so you can't really go uphill on it, and if you're going on a straight road or downhill, you can't pedal any faster, but there is still room for speed because on a speed bike, you could go as far as gear 18 or 21.

And could you please elaborate a little more on the mechanism used to transfer the rotating motion from the gears all the way to the propeller.

I design my drive system and prop so everything is tuned to my sustainable power level. This is 130W. My preferred cadence is 70 to 75rpm. In calm conditions I can get 11kph with 130W.

If I want to go faster I pedal faster and the leg forces go up. My maximum power level is around 120rpm using 175mm cranks. The gym machines I use are limited to 630W so this is the highest I have seen but it is very close to my maximum output. A sprint cyclist might get to 1500W or more.

If I want to ease up I pedal slower. The forces get lower.

The reason you have gears on a bike are to accelerate and to go up hills. I can get my prop to suck air and spin without load at zero speed. In fact if I want to accelerate quickly I have to get sufficient boat speed before I can really apply force. In a race I can outpace paddlers to 14kph which is near the top speed for most of them. It only takes a second or two to reach that speed - would be wasteful fiddling with gears.

Most water does not have big hills where gearing is beneficial on a bike.

This picture shows the curved spring steel shaft I commonly use on boats:
http://www.boatdesign.net/forums/attachments/boat-design/32172d1243890965-adirondack-challenger-texas-water-safari-v11j_prop_curved_shaft.jpg

Some have tried freewheeling props so they can stop spinning but then you lose the ability to go in reverse and this is extremely useful on the water. Without a freewheeling hub you might find changing gears a bit more complicated. Relying on a spring take-up on the chain will also limit the ability to apply power in reverse.

There have been rare times when I would have liked a lower gear when pushing into strong headwinds for hours on end. My knees start to give up before the rest of my body due to the load on the legs.

Rick W

[Pedaler]

Trasmission, by definition uses the mechanics advantage that provides a speed-torque conversion. The numbers you are telling me about what you do at the gym and on the boat don't really speak to me as I'm not in the boating business (yet). But when you reach that 120rpm maximum, what if you had multiple gears and you switched to the next gear? What exactly would happen to the speed of the boat and to your fatigue?

[Guest625101138]

Trasmission, by definition uses the mechanics advantage that provides a speed-torque conversion. The numbers you are telling me about what you do at the gym and on the boat don't really speak to me as I'm not in the boating business (yet). But when you reach that 120rpm maximum, what if you had multiple gears and you switched to the next gear? What exactly would happen to the speed of the boat and to your fatigue?

The 120rpm is not my maximum cadence. I can comfortably spin 175mm cranks to 140rpm. Some using 145mm cranks spin over 200rpm.

If was sprinting at 120rpm and changed to a higher gear the forces on my legs would be too great and I would loose speed rapidly. It is the same sort of situation you would find in your car if you were climbing a hill and you shifted up rather than down. The speed would collapse. You have exceeded the torque capacity of the engine.

Rick W

[Pedaler]

Well then, in that case, could I still utilize the old mountain bike with all its gears in place even though I might have realized that I don't really need so many gears on a boat? I just don't have a single-speed bike to salvage.

Now that we've passed the gears question, as I imagine the part that I will most likely have to pay for is that right angle converter. What is it called properly and where is it mounted on the bike so that I will be able to reverse?
I noticed from the other thread that they go for several hundred dollars. Are there not MUCH cheaper alternatives?

[Ad Hoc]

"...Foils are 2 to 3 times more efficient than a planing hull..", what kind of foil, what kind of hull, what displacement what speed what aspect ratio what chord etc etc?? Reference, or just the usual numbers plucked from thin air???

Pedaler
The reason why narrow tip propellers are shown to be efficient in smooth water trials is that the thrust requirement is low, since a high proportion of the total load on a propeller blade is carried by the tip; therefore local breakdown of flow may occur.

So, it depends on how much thrust you can deliver not at the gears of you bike, but at the propeller, and how much thrust, or drag there is, required from you boat for certain speeds. Then how to deliver that thrust through the speed range.

[Guest625101138]

The simplest way to use the bike is to just have a straight chain run from the chainring on the cranks to the input shaft of the gearbox. Anything involving a normal hub will preclude reverse and I expect this will be a serious nuisance.

You will have to be careful how the bike frame is mounted because there is a need to consider stability in a boat. If you sit up high and get a few waves you will end up very wet under the boat rather than on top. There are some pedal boats operating with high seating positions but they are either very stable catamarans or dynamically stabilised narrow hulls with slow speed or emergency outriggers that are deployable.

You might be lucky and jag a cheap box on Ebay. I know a couple of people who have picked up new or near new boxes for a fraction of their original cost. The Mitrpak are probably the best value and they are lower cost than many.

Rick W

[Guest625101138]

......
I noticed from the other thread that they go for several hundred dollars. Are there not MUCH cheaper alternatives?

There are cheaper alternatives but none are as good as the precision cut spiral bevel gears with ball bearing supported shafts.

I have not tried the open nylon gears shown here:
http://www.teausa.net/admin/uploads/TEAUSARightAngleDrives.pdf
The 15mm shaft size will handle your power. The 12mm shaft would be marginal.

Another very cheap option for doing some mucking about is a right angle drill attachment like this:
http://www.made-in-china.com/image/2f0j00PeJQTWdghHcDM/Right-Angle-Drill-Attachment-with-Keyless-Chuck-ST-RAD01-.jpg
They can be picked up for under $10 in most hardwares. It will last about 5 minutes but costs little. They are difficult to mount and you can get them to last a little longer if you stiffen up the case by encapsulating. I know of one older fellow who used one for more than a year without breaking it.

Some of the little electric grinders have nice gears and these can be set up to work for a period. They often wear out brushes and it is not worth replacing the brushes so they get thrown out.

The cheap solution would allow you to do a proof of concept just to gain an idea of what it feels like. Take a paddle so that when it fails you can get back to shore easily.


Rick W

[Pedaler]

Thanks for the help. I've found a Mitrpak, but it's the MITRPAK T081. Do you know if that would suit my needs? If it won't work out with it, then where exactly would I get the cheaper right angle solutions? I imagine mounting the drill attachments would indeed be quite difficult.

[Rangerspeedboat]

Just had a really simple solution come to mind. A paddle wheel boat.

Have 2 sidewheels powered by your bike which the sprocket from the rear wheel just going to the paddles. You can change gears and all that, it might be more efficient than having gears on a prop.

Or your bike powering a set of oars, which would basicly be the same thing.

[Pedaler]

Also an interesting idea, but I think the one with the propeller is easier for me to start with. Just the right angle converter is needed, some sort of shaft and some clever bike mounting in my original project. Plus, when I saw that vintage video of the human powered boats competition, the paddlewheel designs mostly ended up being last, and a boat with two guys and a propeller won.

[Village_Idiot]

If gears were a good idea in boat propulsion, we would likely see them widely implemented.

As was explained to me a long time ago, operating a motorboat is comparable to driving a car at high rpm and driving uphill wherever you go. There is a huge difference in a bicycle or car coasting down the road vs. a boat pushing through the water. While most modern cars have engines producing well upwards of 100hp, it only takes around 5-10hp to keep the car going down the road - the extra hp is used for acceleration, climbing hills, towing, etc. The boat is always using the majority of its hp to push through the water.

As Rick pointed out, much more application of power generally results in cavitation at the prop.

Perhaps it would be more efficient to modulate the angle of attack of the prop blades (like a helicopter) rather than to fiddle with gears in the driveline.

At the very least, you could play with prop venting as is done in high-performance props (allows air (or exhaust, in the case of outboard engines)to access the prop blade at low rpms to reduce water resistance at low speeds, then becomes nonsignificant once cruising speeds are reached) - this allows for higher-pitched blades than would be possible with a given amount of power.

[Pedaler]

Yes, I've been coming to the realization that gears perhaps aren't very important or needed in a boat from Rick's posts already. However now, the question stands about what right angle converter to use, where to mount it on the bicycle, and what sort of metallic shaft to utilize, and how to utilize it when it goes from the right angle converter to the propeller.


Edit:

I still do think that leaving the gears in place will allow me to use them beneficially. Personally, I am quite an avid fisherman, hence the need to use my big old flat bottom boat. There are close destinations where I could get on a hard gear to pedal for just a few minutes, but to go very fast, and there are long distances I want to go to, where I would select an intermediate gear which would utilize my leg muscles most efficiently so that I could pedal comfortably the whole way there.

[Guest625101138]

Thanks for the help. I've found a Mitrpak, but it's the MITRPAK T081. Do you know if that would suit my needs? If it won't work out with it, then where exactly would I get the cheaper right angle solutions? I imagine mounting the drill attachments would indeed be quite difficult.

I have attached the data sheet for the T-081. It is close to ideal. The "T" configuration offers more flexibility as you do not have to worry about the direction of rotation of the prop. You can change rotation by flipping the box. If you look closely at the photos of my boasts you will see they use a "T" type box.

You now need to get a sprocket for the shaft that will accept bike chain.

Building something like this is easier if you have access to some basic workshop capability.

Rick W

[Pedaler]

How exactly will the sprocket be utilized in my setup? Why can't I just use the sprocket from the bike's gear system?

[Guest625101138]

How exactly will the sprocket be utilized in my setup? Why can't I just use the sprocket from the bike's gear system?

The shaft on the bike is fixed. It does not rotate. You need to find a way to get one of the small sprockets from the cassette onto the gearbox. Or buy something like a 12T or 14T sprocket and mount it on the shaft.

The only items of use on the existing drive train are the chainring, bottom bracket and cranks. The rear wheel will need to be removed.

Rick W

[Guest625101138]

I have used a MTB 15T sprocket welded to a metal boss and fitted that on a gearbox shaft but I find it easier to buy a standard 14T sprocket and modify it to suit the narrow bike chain.

Rick W

[Pedaler]

Though I see the sprocket isn't really too expensive, I haven't been planning on such a complicated mod. I imagined that I will be leaving the back wheel on for some reason. I guess it should come off, but I have never even tried to disconnect the gears from the back wheel. Can't really imagine how I would mount the bike on its forks and install the sprocket to work together with everything. How can I retain my ability to switch gears in this setup?

[Guest625101138]

Though I see the sprocket isn't really too expensive, I haven't been planning on such a complicated mod. I imagined that I will be leaving the back wheel on for some reason. I guess it should come off, but I have never even tried to disconnect the gears from the back wheel. Can't really imagine how I would mount the bike on its forks and install the sprocket to work together with everything. How can I retain my ability to switch gears in this setup?

As you get into it you will see that the bike and the boat do not go well together. By the time the bike frame is set high enough for the cranks to clear the bottom of the boat you will be sitting quite high and the boat will be marginally stable.

The easiest and best set up would be to cut the bottom bracket out of an old frame with about 300 to 400mm of tube on either side. This gets inverted and mounted to a plate that fits in the bottom of the boat. You would get a nice comfy seat to mount on the rear box seat of the boat so you can pedal in a seated position. It would be semi-recumbent.

The gearbox would be low in the hull with a small sealed shaft tube that penetrates the hull. The prop would mount just behind the transom on a springy curved shaft so it can be pulled up for beaching.

I can draw this up if you are interested. This would be a more serviceable set up and make the expense of the gearbox worthwhile. Anything involving the upright riding position of the existing bike frame will be ungainly and bordering on unsafe when in operation.

Gears are an unnecessary complication. Riding on the water is very much akin to riding up a long steady incline that just goes on endlessly. Taking time to change gears means you quickly lose speed and have to start over. Cyclist that take it up soon learn that there is no coasting. Stop spinning and boat soon stops. Glides on somewhat more if the prop freewheels but then no reverse.

I can give you better targetted information if you let me know what workshop facilities you have access to. Things like brazing, welding, milling, turning, drilling, grinding, fibreglassing etc.

Rick W

[Guest625101138]

In terms of expectations what speed are you hoping to achieve with this pedal powered boat?

Rick W

[Pedaler]

I am greatly interested in seeing a drawing if you could make one. In regards to speed, the faster the better. The whole point is to have my hands free while moving the boat (as I mentioned I am a fisherman) and the second point is for the fun of it, especially if I can make it work with gears. I don't know what exact speed I am aiming at. If I row at an average of 8mph, (whatever the speed is, I don't know) then I want the propelled boat to go about that speed. If it can't do any faster, it's not much of a problem because I still have my hands free when moving, but if my rowing average is 8mph, then a max of 4mph with the propeller would really be unexceptable.

[Pedaler]

In regards to the workshop facilities, VERY limited. No welding at all. Pretty much drilling I can do, and grinding I guess. Very limited powertools. Actually, the only power tools I have so far are a drill and a saw. Got lots of hand tools, and a friend who has several lots of stuff which I would probably be able to use. But so if you can give more specific directions/instructions, try to treat the situation as a given that I have minimal equipment.

[Guest625101138]

You may be able to manage 4mph while rowing. You may get the boat to 5mph with pedalling if it is set up well - bit more if you really put full effort into it. The boat is not a speed demon. Its shape, with typically human power level, condemns it to slow speed.

I will draw it up tonight. Can you give me the hull dimensions; just length beam and height to save me estimating?

The easiest way to assemble it all is with epoxy and glass tape if you cannot weld thin wall steel tubing used on the frames.

Rick W

[Pedaler]

Thanks. Take the dimensions from here: http://www.academy.com/index.php?page=content&target=products/outdoors/marine/boats&start=0&selectedSKU=0141-00124-1032 The boats are serial so mine is most probably the exact same size and shape. It looks 100% the same anyway. Thanks again.

[Guest625101138]

I have attached a 3D image of the proposed configuration. I have used a rendering of one of my boxes rather than the Mirpak but they are similar. The Mitrpak is slightly smaller.

This is intended to show how the inverted bike frame would be used. I can describe ways to mount the gearbox that you should be able to achieve. There are some basic parts you need to get. If you have a tight budget it will be worthwhile pricing all the things before you jump in. Also some bits may be hard for you to get. Some things will be best done by connecting to the existing boat and you need to decide how permanent these will be. A hole in the hull will be difficult to patch neatly without welding ability and there may not be a big market for the boat.

I expect you will enjoy it and it certainly leaves hands free. It will attract a lot of attention so you have to be prepared to deal with that.

I have no idea where "yes" is so cannot make meaningful suggestion where you might look for parts.

You should be able to sustain about 4.5mph and hit around 7.5mph at full tilt for a short period. This assumes you are an adult male of average weight and fitness level.

Rick W

[Pedaler]

Thanks for the drawing. My location is NY, USA so I don't even expect you to be able to hint any specific stores. Regarding the permanence of the setup, if I realize that the whole idea is worthless, I'd still like to be able to use my boat the normal way, without the bike on top of it. So if this mod can't be done as a put-on, take-off mechanism, then at least it shouldn't do any serious permanent damage to the boat so that I can still use it normally.

I guess you could say that I am an adult male, I'm 19 years old and ride my bikes often, especially in the summer, I ride them for miles every day.

If you could please, go on and show me how I can mount the gearbox.

[markdrela]

Rick Willoughby is correct. There's little or nothing to be gained from gearing a pedal boat. Below is message I posted on rec.bicycles.sci a long time ago which addresses this in more detail:



Subject: Lake runner impressions

To answer some of Dan Gold's questions...

Variable gearing makes little sense for a propeller
on a HP boat. The terrain is usually quite flat :-).
But seriously, a prop of fixed geometry designed for
a certain boat-speed/power/rpm combination will remain
nearly-optimal for a very wide range of operating
conditions. The prop's power absorption capability
varies as V^3, while its operating rpm varies as V.
This closely matches the power demands of a displacement
hull (assuming skin friction dominates), as well as the
cadence requirements of the rider. For example, if the
Lake Runner at 6 mph requires 150 Watts (0.2 hp) at
65 pedal rpm, at 10 mph it will require 690 Watts (0.9 hp)
at 108 pedal rpm. Both power/rpm combinations are
reasonable, and in each case the prop will be at its
design condition.

The biggest reason for changing the gear ratio is to
compensate for different-sized riders. A bigger rider
will inherently put out more power and go faster, requiring
a larger gear ratio (i.e. a "bigger" gear) to keep the rpm
the same as that for a smaller rider. In this situation,
the gear ratio wants to vary as Power^1/3, which is a
pretty weak dependence. With a hydrofoil the dependence
is even weaker.

Another reason to increase the gear ratio is when going
downwind, in order to compensate for the higher speed
and rpm at a given power level. I can't see such an
air-drag effect being too significant on a relatively
slow vehicle like the Lake Runner.

In theory, there is little difference between water
and air props. An air prop must be about 30x bigger
than an equivalent water prop to compensate for the
density difference. The Decavitator's 10 foot diameter
air prop is equivalent to a 4 inch water prop. The
advantage of the air prop is that it turns about 30x
slower, and hence requires much smaller gearing step-up
from the pedals. This translates to smaller drive
losses, and also avoids the draggy surface-piercing
drive shaft and prop-mounting strut. Disadvantages
of the air prop include the big overall size, nose-down
moment from the high thrust line, and nasty side moments
from crosswinds.

The prop disk area (i.e. diameter) is strongly dictated
by the operating speed, power, and fluid density.
The non-dimensional power coefficient

Pc = 2 x Power / (disk_area x rho x V^3)

should not exceed ~0.2 for good efficiency. The Lake
Runner's prop looks far too small for the claimed speed.
It may be blowing off an additional 10-20% power as a
consequence. I guess they compromised performance to
get a small draft.

Using a hydrofoil only makes sense above ~10 mph.
Below this speed a good displacement hull like a racing
kayak has less drag.

[Pedaler]

I see. But as I do not have access to a wide range of propellers and am on quite a tight budget, I won't be able to pick out the most ergonomic propeller for me. Hence, if I'm stuck with one that requires a lot of power, I'd be able to utilize it at an easier gear. Like you said, heading downwind would make it reasonable to switch gears to a more powerful gear. And vice versa.

[Guest625101138]

Thanks for the drawing. My location is NY, USA so I don't even expect you to be able to hint any specific stores. Regarding the permanence of the setup, if I realize that the whole idea is worthless, I'd still like to be able to use my boat the normal way, without the bike on top of it. So if this mod can't be done as a put-on, take-off mechanism, then at least it shouldn't do any serious permanent damage to the boat so that I can still use it normally.

I guess you could say that I am an adult male, I'm 19 years old and ride my bikes often, especially in the summer, I ride them for miles every day.

If you could please, go on and show me how I can mount the gearbox.

If you do this well you will have something that is very pleasant to operate and you will never want to use paddles again.

The most serious permanent consequence for the hull will be a small hole that will need to be plated over if you want to remove the drive. This can be done quite neatly and will certainly not bother you from a rowing perspective.

For this reason I think the shaft tube will be the most demanding for you.

There are a few ways to do this and you will need to find compatible bits. The tube has to accept a bearing and a lip seal. Their size will depend on the prop shaft you use.

The first step is to determine what shaft you can get. Spring 8mm or 5/16" steel is the best but you may have trouble finding this. The next best is 10mm machinable aluminium.

Once you find what shaft material you can get you select the bearings and seal. I have attached photos of the sort of things I use regularly. I get these from a firm called "smallparts" and they have warehouses in the US. They provide good service and prices are OK. If you have a general power transmission firm near you they might have these things on the shelf. Get bearings with stainless balls and metal shields.

The OD of the bearing and seal will set the ID of the shaft tube. You can use various materials for the tube such as rigid PVC, HDPE or aluminium. The tube will be glassed to a wooden flange that is screwed to the hull. A small hole will be drilled though the hull to enable the shaft to pass through. The wooden flange will be approximately 4" wide and 6" long and will have half rounds on either end that are a neat fit in the stiffening ridge of the hull.

The shaft tube will come up out of the flange at an angle of 20 degrees.

Setting up the shaft tube will be the hardest part. It has to be done neatly with the miniumum permanent changes to the hull.

This link shows the sort of prop that you can use:
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5529&Product_Name=JXF_15x13_/_381_x_330mm_Poly_Composite_propeller
The pitch is a bit low but will be OK to get you going and is not expensive.

To start you need to find a suitable shaft. Let me know what you come up with. Bright steel will be adequate for a test but will not last indefinitely. You need a length of 6ft if they will cut it. I can only get the heavier spring steel in minimum order lots of a few hundred dollars so I do not expect you will be doing this. Anything but mild steel will work.

Rick W

[Pedaler]

The project is getting more and more complicated the more you describe the parts and work needed for it. To be honest, I don't understand more than half the terminology you're using. I will either have to resort to doing it the simplest, thought probably least efficient, way possible, or drop the project altogether. I don't have much time and resources, and when I thought about it at first, it seemed like something that I could fashion using scrap from the garage and a few days of my time at most. The Mitrpak that I had my eye on ended up going for quite some money still on ebay, and I just don't have such a keen eye in this exact field to be able to see things in the hardware store that I could use to substitute the right angle gear box.

[Ad Hoc]

Pedaler
"...The project is getting more and more complicated the more you describe the parts and work needed for it..."

This is because your focus and RW's focus is totally different. Your original idea is sounds, no problem, it is fun and have a go. But if you wish to pursue to the n'th degree for very small increases in efficiency etc, which on your project will never be realised, you can.
But as a project, a nice little exercise for fun, do it. Ignore the "..if you do XXX you gain better efficiency..etc".
This is a small fun project, all you want is the means of how to make it work. Whether it works as the most efficient machine built by man ever i think is not your objective, unless I am wrong. Your objective is to put your idea, on the water..regardless of its flaws. All boats have flaws, it is called a compromise.

If you build it....it will float ;)

[Pedaler]

Yes, Ad Hoc, you've got the right idea. I appreciate Rick's professional and detailed posts greatly, but they are from his world record winning background, and I'm just after the proof of concept for myself, without any need for competition, or market. So Rick, can you simplify the instructions by say, 100 times?

[Guest625101138]

Paddles are simple and convenient. They are still competitive with more modern technology.

If your build is not thought through using suitable parts it will fail often and just be a source of annoyance and great frustration.

There is some interesting pictures and commentary on HPBs down the linked page:
http://www.wisil.recumbents.com/home.asp?URL=wisil/hpb/boat.htm
You will see race results and pictures for the various years. Some of them have to be rebuilt after each race day because they break down regularly.

These boats tend to be fun for people who like to tinker. There are some successful commercial boats like the Hobie Mirage but most people stick with paddles.

Even if you decide not to proceed then you can take some satisfaction from the fact that the fastest man on water took the time to respond to your thread and provide some advice on gears:
http://www.youtube.com/watch?v=l2UOH65QOI4

Rick W

[Ad Hoc]

professional advice is a subjective term too.

A professional naval architect (which RW is not) would not be giving advice in this way. A details person on one subject, as RW is, is helpful in that very narrow band and he can provide lots of little details of just that subject.

So you need to decide yourself first what advice in which area you wish, overall design/concept, or the details of how bits fit together to get the deisgn to work.

The person giving the advice must also be able to recognise your limitations and provide guidance accordingly. No point blinding you with science. Just as no point explaining spin/charm and colour of quarks to a high school student just starting physics, is it?

Advice/guidance is only helpful to the precipitant if it is clear, concise and answers the question asked.

[Pedaler]

Rick I do apprecieate your help, and I do understand why you're stressing me to go with the proper materials, tools, and building for my project, but the circumstances just don't allow that for me. Think of it like a hobby with a very minimal amount of money set to spend, quite a bit of time, and not many tools for it.

Would you say that even my boat, with the proper gears and propeller setup can be made more efficient and convenient than when it is used stock with the oars? If so, then how come we see so many row boats and so few pedal+propeller boats? My point is that it's probably still not such a no-brainer to use pedals and a propeller on boats, especially non-competition boats, so I just want to try the idea for the fun of it, especially because I'll realize that going with good ol' oars is still better.

[Pedaler]

professional advice is a subjective term too.

A professional naval architect (which RW is not) would not be giving advice in this way. A details person on one subject, as RW is, is helpful in that very narrow band and he can provide lots of little details of just that subject.

So you need to decide yourself first what advice in which area you wish, overall design/concept, or the details of how bits fit together to get the deisgn to work.

The person giving the advice must also be able to recognise your limitations and provide guidance accordingly. No point blinding you with science. Just as no point explaining spin/charm and colour of quarks to a high school student just starting physics, is it?

Advice/guidance is only helpful to the precipitant if it is clear, concise and answers the question asked.


I agree, but I also value and appreciate the time Rick put in answering my questions and sharing his wealth of knowledge. Though he probably lost track of the simplicity that I desire in my project, his advice provided great knowledge towards my idea either way.

[Guest625101138]

.... So Rick, can you simplify the instructions by say, 100 times?

The concern that I have for the shaft tube is that it requires some permanent change to the hull. If it is not done neatly then you will not be able to remove the shaft and make a simply repair.

The alternative of sticking the gearbox on the stern or side of the boat creates much greater complexity in setting up the transmission.

First step is to find suitable material for a shaft. Can you get 8mm or 5/16" spring steel? If not then can you get 10mm or 3/8" machinable grade aluminium? If neither of these then what can you get. Mild steel will not be good enough.

Rick W

[Pedaler]

I have no idea where I could get either spring steel or machinable aluminum off the top of my head. The shaft is the "stick" going from the gears to the propeller, correct? Are there any online sources where I could cheaply acquire this material? Or perhaps some sorts of local businesses that are bound to have this kind of material?

[Guest625101138]

How about you email me and I will give you some leads. It will speed the process.

rickwill@bigpond.net.au

Rick W