Right angle/ bevel gear boxes.

[Artifex75]

I've been reading through the mammoth pedal powered boat thread and I've heard a lot of talk about 'cheap right angle gearboxes'. The cheapest I can find start at $140 and seem way over the top for what I need. Is that about as cheap as it gets?

I'm way too broke to buy a factory drive leg, so this is all diy. I'd lust like to get my hands on a bevel gearbox a little cheaper than that, if it exists.

What about a shaft-driven bicycle? Could it be harvested for parts if I could find one? I can't get any shaft drive bike manufacturers to even give me a price on a part. One said "We don't sell parts, only whole bikes." I said, "So if I buy a bike and the gearbox breaks, you can't sell me a new one?" "Uhhhh......", he said.

So, any help or links that you could pass along would be greatly appreciated.

[portacruise]

Some have used gearbox from large angle grinder such as these:

http://www.alibaba.com/showroom/angle-grinder-gear.htm

Some discussion here:

Pedal Powered Boats

Porta

[Squidly-Diddly]

gears are the weak link, so good luck finding a donor with good gears.

http://www.toolpartsdirect.com/cgi-b...r/1350K_TYPE_1

But I'd think these burly low speed gears would be better for pedal driven apps than a 10,000rpm grinder

[Squidly-Diddly]

http://www.mcmaster.com/#miter-gears/=btqbqx

• Spur, Worm & Miter Gears
  
  For information about gears, see page 1054.
  

Steel 20° Pressure Angle Spur Gear Rods Make your own spur gears from our steel gear stock, which has been cold rolled for strength. The teeth are already formed so you can easily machine custom face widths and bore sizes. Rods have a polished finish. Furnished in 1-ft. lengths.
Note: Choose spur gears and racks with the same pressure angle and pitch. The 14 1/2° and 20° pressure angle spur gears and racks are not compatible.
Pitch No. of Teeth Pitch Dia. OD Each
32120.375"0.44"6847K11$22.6632200.625"0.69"6847K1228.5632321"1.06"6847K1342.7632401.25"1.31"6847K1452.3924120.5"0.58"6847K1524.6124160.667"0.75"6847K1628.9324200.833"0.92"6847K1734.5724241"1.08"6847K1841.0920120.6"0.7"6847K1925.7320160.8"0.9"6847K2132.0420201"1.1"6847K2239.6716120.75"0.88"6847K2428.7016161"1.13"6847K2536.3116201.25"1.38"6847K2642.7316241.5"1.63"6847K2754.2312121"1.17"6847K2838.8012161.333"1.5"6847K3150.7012242"2.17"6847K3283.87

14 1/2° Pressure Angle Worm Gears and Worms Designed for use on 90° angle parallel shafts, these worm gears and worms produce a high speed-reduction ratio in a minimal amount of space. Speed-reduction ratio is determined by the number of teeth. For example, a 20-tooth worm gear and its mating worm will give you a 20:1 ratio and will reduce 200 rpm to 10 rpm.
Worm Gears— All are cast iron and have a plain bore. Worms— Made of steel, these worms have right-hand threads and a standard ANSI keyway (see page 1160 for keyway dimensions).

Worm Gears
No. of Pitch Hub OD O'all Teeth Dia. (A) Dia. (B) (C) Lg. (D) Bore Each
12 Pitch— 1/2" Face Width 181.5"1 1/4"1.69"1 1/8" 1/2"57545K511$51.73201.67"1 1/4"1.85"1 1/8" 1/2"57545K51353.05302.5"1 1/4"2.69"1 1/8" 1/2"57545K51561.67403.33"1 1/2"3.52"1 1/4" 5/8"57545K51767.39605"1 3/4"5.19"1 1/4" 5/8"57545K52290.3210 Pitch— 5/8" Face Width 202"1 1/4"2.22"1 3/8" 1/2"57545K41155.96303"1 3/4"3.22"1 3/8" 5/8"57545K41370.33404"1 3/4"4.22"1 3/8" 5/8"57545K41584.78505"2"5.22"1 3/8" 3/4"57545K41797.7510010"2"10.22"1 3/8" 3/4"57545K424161.918 Pitch— 3/4" Face Width 202.5"1 3/4"2.78"1 1/2" 3/4"57545K31165.41303.75"1 3/4"4.03"1 1/2" 3/4"57545K31390.32405"2 3/8"5.28"1 5/8"1"57545K315111.766 Pitch— 1" Face Width 203.33"1 7/8"3.71"1 7/8" 3/4"57545K21197.75244"1 7/8"4.37"1 7/8" 3/4"57545K213112.29305"2 1/4"5.37"1 7/8" 7/8"57545K215136.27406.67"2 1/2"7.04"1 7/8"1"57545K217176.817212"3"12.37"2 1/4"1 1/4"57545K244253.66Worms
Pitch Pitch Dia. (E) OD (F) Face Wd. Bore Each
121"1.17"1 1/8" 1/2"57545K527$25.07101 1/4"1.45"1 3/8" 5/8"57545K42735.6181 1/2"1.75"1 3/4" 3/4"57545K32751.0162"2.33"2 1/2" 7/8"57545K22769.36
20° Pressure Angle Miter Gears Miter gears transmit motion and power at a 1:1 ratio between shafts that intersect at right angles. To mesh properly, they must be positioned at right angles and have the same pressure angle, pitch, and number of teeth. Molded nylon gears are lightweight, quiet, and corrosion resistant. Hardened steel spiral gears offer quieter operation, higher speeds, and greater torque than the nonspiral gears. Molded nylon and steel miter gears are sold individually; use two gears together to create a set. Hardened steel miter gears are sold in sets of two.
Choose miter gears with a plain bore or with a finished bore. Gears with a finished bore are ready to mount and include a set screw and standard ANSI keyway (see page 1160 for keyway dimensions).
No. Pitch Hub O'all Face Mount. of Dia. Dia. OD Lg. Wd. Lg. Teeth (A) (B) (C) (D) (E) (F) Bore Each
Molded Nylon Plain Bore Miter Gears 48 Pitch 180.375" 21/64"0.4" 9/32"0.09" 13/32" 1/8"7297K11$2.76240.5" 3/8"0.53" 3/8"0.13" 17/32" 3/16"7297K122.7632 Pitch 160.5" 13/32"0.55" 11/32"0.13" 1/2" 3/16"7297K132.76240.75" 1/2"0.8" 13/32"0.13" 11/16" 3/16"7297K142.8524 Pitch 241" 5/8"1.05" 9/16"0.22" 29/32" 1/4"7297K153.16301.25" 5/8"1.31" 37/64"0.22"1 1/32" 1/4"7297K163.17361.5" 11/16"1.56" 39/64"0.3"1 3/16" 5/16"7297K173.1916 Pitch 161" 3/4"1.09" 3/4"0.25"1 1/16" 3/8"7297K183.94Steel Plain Bore Miter Gears 16 Pitch 161" 3/4"1.09" 3/4"0.22"1 1/16" 3/8"6529K1116.57201.25"1"1.34" 27/32"0.27"1 1/4" 7/16"6529K1318.90241.5"1"1.59" 7/8"0.31"1 3/8" 1/2"6529K1621.5212 Pitch 151.25"1"1.37" 55/64"0.27"1 1/4" 3/8"6529K1419.47151.25"1"1.37" 55/64"0.27"1 1/4" 1/2"6529K1519.47181.5"1 1/4"1.62"1 1/64"0.32"1 1/2" 1/2"6529K1722.80181.5"1 1/4"1.62"1 1/64"0.32"1 1/2" 5/8"6529K1822.80211.75"1 3/8"1.87"1 3/16"0.39"1 3/4" 1/2"6529K1923.84211.75"1 3/8"1.87"1 3/16"0.39"1 3/4" 5/8"6529K2123.84242"1 1/2"2.12"1 7/32"0.43"1 7/8" 1/2"6529K2227.78302.5"1 3/4"2.62"1 31/64"0.54"2 5/16" 5/8"6529K2640.7110 Pitch 202"1 5/8"2.14"1 23/64"0.44"2" 1/2"6529K2332.11202"1 5/8"2.14"1 23/64"0.44"2" 5/8"6529K2432.11202"1 5/8"2.14"1 23/64"0.44"2" 3/4"6529K2532.11252.5"2"2.64"1 5/8"0.55"2 7/16" 3/4"6529K2745.35252.5"2"2.64"1 5/8"0.55"2 7/16"1"6529K2945.35Steel Finished Bore Miter Gears 16 Pitch 161" 3/4"1.09" 3/4"0.22"1 1/16" 3/8"6843K1133.16241.5"1"1.59" 7/8"0.31"1 3/8" 1/2"6843K1239.0912 Pitch 151.25"1"1.37" 55/64"0.27"1 1/4" 1/2"6843K1330.82181.5"1 1/4"1.62"1 1/64"0.32"1 1/2" 5/8"6843K1436.05211.75"1 3/8"1.87"1 3/16"0.39"1 3/4" 5/8"6843K1537.08302.5"1 3/4"2.62"1 31/64"0.54"2 5/16" 5/8"6843K1658.2710 Pitch 202"1 5/8"2.14"1 23/64"0.44"2" 1/2"6843K1746.64202"1 5/8"2.14"1 23/64"0.44"2" 5/8"6843K1846.64202"1 5/8"2.14"1 23/64"0.44"2" 3/4"6843K1946.64252.5"2"2.64"1 5/8"0.55"2 7/16" 3/4"6843K2160.31252.5"2"2.64"1 5/8"0.55"2 7/16"1"6843K2260.31No. Pitch Hub O'all Face Mount. of Dia. Dia. OD Lg. Wd. Lg. Teeth (A) (B) (C) (D) (E) (F) Bore Per Set
Hardened Steel Finished Bore Spiral Miter Gear Sets —2 per set18 Pitch 181" 3/4"1.07"0.74"0.22"1 1/16" 3/8"7655K1$113.2112 Pitch

[Lurvio]

I bought a whole angle grinder for 20 euros a while back, from Biltema.

The gearbox is aluminium and has 4:1 gearing, which I believe is quite ordinary. The disk side utilisation is quite easy, the motor side is a bit trickier, mine had the smaller cog removable (has a key), but some might have the smaller cog machined to the motor axle which is a whole lot harder to use. I am going to machine a new shaft stump to the motor side of the box and glue (bearing glue - releases when heated to 150 celsius) the cog to it.

[Poida]

Every time you change direction of drive ie bevel gears you are going to lose power (fiction)

If you can use paddle power used in the same drive plane as the pedal motion you will transfer more power.

Other than that you can use wheels with a solid rubber rim at 90 deg.

[Squidly-Diddly]

you will need two so $8

7297K18Molded Nylon 20 Deg Pressure Angle Miter Gear 16 Pitch, 16 Teeth, 1" Pitch Dia, 3/8" BoreIn stock at $3.94 Each

From McMaster-Carr.


If you are able to strip those with your mighty leg muscles while "burning water" you can try steel gears for....

6529K11Steel Plain Bore 20 Deg Angle Miter Gear 16 Pitch, 16 Teeth, 1" Pitch Diameter, 3/8" BoreIn stock at $16.57 Each THEY MEAN TWO....

read following....

Miter gears transmit motion and power at a 1:1 ratio between shafts that intersect at right angles. To mesh properly, they must be positioned at right angles and have the same pressure angle, pitch, and number of teeth. Molded nylon gears are lightweight, quiet, and corrosion resistant. Hardened steel spiral gears offer quieter operation, higher speeds, and greater torque than the nonspiral gears. Molded nylon and steel miter gears are sold individually; use two gears together to create a set. Hardened steel miter gears are sold in sets of two.
Choose miter gears with a plain bore or with a finished bore. Gears with a finished bore are ready to mount and include a set screw and standard ANSI keyway (see page 1160 for keyway dimensions).

[Jeremy Harris]

Remember that if you're going to use the gearbox direct from the pedal cranks then the gear tooth torque rating has to be pretty high, meaning big gears.

As an illustration, most people can easily push their whole body weight with one leg, say a force of around 800N (around 180lbsf), peak leg force may be double this figure. Bike cranks are around 170mm long usually, so the torque at the pedal crank shaft will be around 136N-m (about 100lbs-ft), maybe double this when you push hard to accelerate.

I very much doubt if small nylon gears will take this load for long without failing. You can just get away with using plastic gears (but a lot bigger than those small McMaster Carr ones) if you opt to do the speed increase (and hence torque decrease) before the right angle gearbox. I have some plastic bevel gears here that were used for a 1:2 right angle pedal boat drive, with a chain drive increasing the rpm at their input. These are about 86mm (~3 3/8") in diameter with 26 teeth, which may give you an idea of what's needed. Even this big a gear needed the smaller, 13t gear to be made from steel to take the tooth load OK.

Jeremy

[BATAAN]

Milwaukee Tool Company's right angle gear drive for 1/2" electric drill is a 3:2 ratio, very heavy duty, and available as an accessory to the Milwaukee Magnum Drill.

[Lurvio]

There is one big problem with buying separate cogs. They all need a housing that has to be darn accurate or the cogs will be short lived. Were talking dimensional accuracy somewhere around .05 mm (.002''). I went trough all this thinking process and without cnc- or other highly accurate heavy machinery I didn't see a way to achieve that.

I'm going to have an overall gearing of 1:10, first a chain connection with 1:2,5 (approx) gearing and the angle gear has the 1:4 gearing.

Lurvio

[BATAAN]

This is a bulletproof thing.

[Jeremy Harris]

Originally Posted by BATAAN

This is a bulletproof thing.

The gears in heavy duty drill right angle drives like this one are rated at around 2 to 6 N-m (around 1.5 to 4.4lbs-ft). They can maybe take double this with some shortening of their life and the risk of gear tooth failure. If this was at the end of a 1:10 ratio change, then the input torque could be around 13.6N-m, peaking at maybe 27N-m for a hard push, so way over the torque that gears this size can take. Overloading them to this degree will pretty quickly lead to early failure, as I found out when using a drill right angle box to drive a 12" slow turning prop - mine lasted about an hour before the gears sheared, not surprising as when I stripped it I found they were mod 1.5 gears, far too small to take the torque of a big prop for long.

The issue here is that you need gears with thick teeth to take the peak torque load at this low rpm. If you do a couple of quick calcs you'll see that this means using gears with a modulus of around 5 or 6 as a minimum. You can easily see from looking at the size of the case that the gears in a small drill gearbox aren't going to be as high a mod as this, they will probably be around mod 1.5 to 2.5 at most.

The gears in a big angle grinder, or better still a slow speed polisher, might be a better bet, as they will be designed to take higher torque loads than a drill and will be bigger, with thicker teeth.

The Mitrpak gearboxes are hard to beat, as they are proven to work well in this application. They have pretty big gears in the ones best suited to pedal boat drives and are able to take the load OK. A look through their spec sheets and a comparison between the torque rating and the physical size will give you an indication of the sort of torque rating that other gearboxes may have - generally the steel used in gears will be similar strength and so size matches closely to torque rating.

Jeremy

[BATAAN]

Originally Posted by Jeremy Harris

The gears in heavy duty drill right angle drives like this one are rated at around 2 to 6 N-m (around 1.5 to 4.4lbs-ft). They can maybe take double this with some shortening of their life and the risk of gear tooth failure. If this was at the end of a 1:10 ratio change, then the input torque could be around 13.6N-m, peaking at maybe 27N-m for a hard push, so way over the torque that gears this size can take. Overloading them to this degree will pretty quickly lead to early failure, as I found out when using a drill right angle box to drive a 12" slow turning prop - mine lasted about an hour before the gears sheared, not surprising as when I stripped it I found they were mod 1.5 gears, far too small to take the torque of a big prop for long.

The issue here is that you need gears with thick teeth to take the peak torque load at this low rpm. If you do a couple of quick calcs you'll see that this means using gears with a modulus of around 5 or 6 as a minimum. You can easily see from looking at the size of the case that the gears in a small drill gearbox aren't going to be as high a mod as this, they will probably be around mod 1.5 to 2.5 at most.

The gears in a big angle grinder, or better still a slow speed polisher, might be a better bet, as they will be designed to take higher torque loads than a drill and will be bigger, with thicker teeth.

The Mitrpak gearboxes are hard to beat, as they are proven to work well in this application. They have pretty big gears in the ones best suited to pedal boat drives and are able to take the load OK. A look through their spec sheets and a comparison between the torque rating and the physical size will give you an indication of the sort of torque rating that other gearboxes may have - generally the steel used in gears will be similar strength and so size matches closely to torque rating.

Jeremy

Great analysis, thank you.

[Artifex75]

Wow. I should have asked before I spend a week googling right angle drives. Thank you all so much. I think that I'm going to check out Harbor Freight for and angle grinder, they've always got something cheap. I've already got an angle grinder, but I'm not quite ready to sacrifice my only one. Give it a week and if I don't find one, it'll probably tear it down in desperation.

I might go ahead and get the steel bevel gears and see if I can manage to put together a box of my own, though my welding skills lean more toward artistic than accurate.

[portacruise]

Here's what Rick Willoughby has been up to in the area of gearboxes (copied from the hpb list). No gear stripping, no friction, no viscoscity losses, etc. with a magnetic gearbox.

Porta


I have been playing around with the idea of making a magnetic right
angle drive unit for a while. Over the past few months I invested in
some magnets and built a prototype:
http://www.youtube.com/watch?v=jCuCmzcjpao

The video shows the torque test. I have a 5kg weight suspended on a
lever arm connected to the output shaft. The lever gets out to 230mm
before the magnets let go. This particular variant has a ratio of
1:3.3 and gives in at 11Nm on the output shaft.

The torque at this ratio is ample for cruising to speed of up to
12.5kph but would give out in a sprint.

The unit was not executed to the initial design because I could not
get the quantity of magnets of the particular size I wanted. It was
intended as a 1:5 step up but I could not get the alignment right
with only 4 magnets on the output so went up to 6 thus reducing the
ratio. However I got better than a commensurate increase in torque.

This unit is extremely robust and heavier than I would want in a
boat. One feature is that the weight is distributed at a large
radius so the crank and output both have high rotational inertia -
flywheels if you like. This leads to smoother pedaling and can
compensate a little for a torsionally compliant prop shaft. Another
feature is the load limiting on the prop shaft.

If I made it to tighter tolerance I could get higher torque. In a
way this would defeat the original idea because I was exploring the
concept for ease of building without need for precision machining.

I expect with ideal magnet selection and simple method of
construction this arrangement could be built for under AUD200.

Rick Willoughby