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A lower engine more user friendly?

G

Gbenzx

Well-known member
Has anyone mounted the auto engine in their Airboat instead of above it for a more stable machine?

Can long belts be used to accomplish this? Do know they have come a long way with belts in last few years.

I can see that an aircraft engine must stay within the airstream for cooling but then they are less weight to roll the boat.

We're thimking of making it as narrow as possible upto abt 14 or 15 but the limits will be in high center of gravity. We don't see a problem in our useage with lower seating.

Thanx, Gben
 
Yes, there are belt drive units that lower auto engines from the prop. They are heavy and VERY expensive. I actually had the idea before I saw one, but after learning they are heavier than a gear box, and that they cost like 2500 plus, I decided against them .

When I can afford it, I will go with a gear box.

The gear box has a hidden benefit: it rotates the prop the opposite direction from the engine, so it counteracts the torque-over of the engine and helps make for a stabler boat. They also lower the engine centerline a slight amount.
 
Thanx agn Red over here on this one :)

Just the opposite of what I would have thot. Belts heavier & more costly than gears.

May try to explore this a little more with search what? Maybe propeller belt or something like that just to see if there has been any changes. The low engine weight can in our case have some priority to a point but not to 8ft wide.

Our whole deal abt Airboat is to work the swamps & go the small creeks & rivers with occasional deep stuff. It will need to run lots of hours in 5 se states. Rather have a little longer than wider sense we can always backup a little with a troller if push comes to shove. Which brings on yet another question which I won't even ask!

May just have to get us a Cub airplane with floats, knock the wings off the damn thing & be done with it.

Thanx Red, Gben
 
I seen those long belt drives and they wight around 4 to 5 hundred pounds so i was told but ther is nothing wrong with putting you motor 4 feet up in the air its just in how you drive it .but a narrow boat won't handle the torque no matter how long it is you need some thing around 7 feet wide any smaller the torque will push the corner under with a car motor. but if you run a 4 cyl air craft you might get away with a narrow boat
 
Thanx CC,

Could not find much on the net abt the wide belt drives but if they weigh up & price up like that drive shafts would be both lighter & less costly.

I will be at a drivetrain shop tomorrow & ask a few questions of someone very sharp in all kinds of adapting & conversion engineering.

If a gearbox is used on say 3-400hp is the roll motion still critical enough to need an 8ft width?

Thimking more abt less power sense hopefully we might never need to climb Niagra falls anyhow :(

Thanx, gben

BTW CC, I meant to say that we've all but ruled out A/C engines because of cost & other variables like chasing for fuel when traveling, magnetoes, etc. We'll just throttle back to around turtle speed & good nuff & we'll get by ok.
 
I'm running a 350 with a rotator box and that only wights around 60 to 80 lbs. my hull is 11 ft 8 in long and 7.5 wide and it handles and rides great with 3 people and 2 batterys and 30 gallons of fuel. my first boat was 11-6 and was 6-6 wide with a driect drive 350 and it would torque so bad that if you didn't cut the rudders when taking off thet it would suck the corner under water.I didn't run any buddy on it just stayed in shallow water to scarey.
 
CC,

That 6.5 wide would really bring on a surprise to the unknowing.
Brings to mind the old Stearman crop sprayers wherein you'd run out of pedal. They were the radial Prat& Whitney 985's at abt 500hp & at full pwr on takeoff you sometimes needed both left feet on the left rudder they used to say. :(

Could someone take a regular little runabout say 15ft or so &modify it into kind of a half & half Airboat. Have no earthly what kind it would be or if any one would have the rear beef enough to stand it. But if the power was kept low maybe there is a brand of some kind that would work out.

Yes I know, bring $10k, we'll talk, bring $10k more & we'll walk & on the 3rd $10k I'll be advised on a finish date!

If a high hp performance category would have tobe used it's probably out the door without further consideration. But what if??? 250hp? It would only need to run wet & guess they are all fiberglass.

Did ya'll just hear a big splash?

Thanx, Gben[/b]
 
Speaking as a person who has just flipped my boat for the second time, I don't see why it has to be so complicated and heavy to put an engine down low. Have you ever seen a belt that takes the place of a chain on a Harley? Pretty stout and they last over 80,000 miles on a bike! Why not just attach a gear out of the engine (down low) and a gear attached to the prop (up high) and run a fat belt between them? Couldn't add more than twenty pounds. I think it's because someone wants to sell you a $2,000 gear unit. Maybe I'll try inventing that after my third flip.
 
You mean sort of like this:

jackshaft1.jpg


There is nothing new under the sun.

The picture came from here:

http://www.1000island.net/~kirawan/

Jim
 
Mongo,

Before I write you this ticket for reckless flying would there be anything you'd like to say for yourself? :D

Just kiddin but seems like everything has tobe in almost perfect harmony or something is going askew. I've been involved in some very risky & close encounters in life & survived to talk abt it. I thimk most that have lived that way simply have a natural need maybe to look for better ways & means.

But whatever you do don't let that thing toss you the 3rd time.

Thanx Cracker for your good info on this site & the Google boys have nothing that comes close :D

But a wood Airboat. With my luck the tearmites would be eatin the bottom & first time I gunned it the motor would launch & i'd still be laying there in the wood.

Looks like they had good intentions however & I'll bet that at least one if not more of the sharp heads on here are starting to think abt it. I believe there may be boats out there already that will fit this very scheme?

Gben
 
Mongo":204ud6qs said:
Have you ever seen a belt that takes the place of a chain on a Harley? Pretty stout and they last over 80,000 miles on a bike! Why not just attach a gear out of the engine (down low) and a gear attached to the prop (up high) and run a fat belt between them?
Click to expand...

Harley makes what, 70hp? And the bikes don't weigh that much. A strong V8 on an airboat would probably strip that belt in short time.

You also need bearings at the top and bottom of the belt, and a structure to hold htem in place
 
The long belt drives seem like they would be great for a 502 or even 454 on a 16 footer, especially in deep water. Or if you were going bigger in deep water, just for stability. Seen those guys on the Madre running airboats in stuff that they are stupid to do. But intelligence and money don't always go together. Look at Mark's Airboats site for some good photos.

Panther made a small 14 footer about 7 foot wide, that was a blast with a ZZ3 belt drive in it. I saw that one scare the hell out of some people that were experienced airboat operators. Made you understand the power of torque and that was with only a 2 blade Power shift.

Gbenz - I have read that quite a few of those old WW2 warplanes have been wrecked in the last 10 years because of that torque. Young guys buy them, take a few lessons and take them out, jam the throttle forward after they are about 10 to 30 feet up to get a thrill. The torque will whip that plane into a ground loop. They just cannot image the power those radials make.

But back to airboats, there are several small rigs that have low powered engines and outboards. It does not require lots of HP to move a rig in shallow water. Especially if you don't want lots of speed. But 20 mph is not bad.
 
Thanx Guys,

And Pat you got the nail on the head one more time abt intelligence & money. In fact very seldom does one find the two together or even at arms length. :)

There is/was something on Inet abt a new type of power transmission via hydraulic transfer in the marine field a while back. But the Google boys have failed me on this one. It was a light weight axial flow(not piston) that was going in boats of some kind somewhere.

About all results I got was the same ole, same ole or half pound of pump/motor for every pound of torque you need. Of course people like Parker buying things out always comes down to less choices.

The quest continues & ducted fans now on the list. Could be two small fans might do the same job with shorter belts & a prop shroud couple feet lower. Anyone know abt their capabilities/limitations?

Thanx, Gben
 
Nice link. I found this

"Our Counter Rotating upper assembly only adds 60lbs. including oil to the weight of your current CH3 belt drive for a total weight of 187 pounds."

That would mean that just the belt drive weighs 137 pounds. Almost like an extra person in the boat!
 
Red - That upper gear in the CH3 are very heavy, don't know how much, but it was heavy. So I would not be surprised if it weighed 135+ pounds.
 
Wonderful, can't we find one that weighs 250lbs?
That way I can tell the tagalong inlaws, these things are not made to Accomadate Everybody, don't wanna sink do you? :(

Really tho thanx guys & great info mudypup.
Now we have to shed something sense two short props will mean shorter belts. First thout was swivel to scuddle the rudders, 2nd was VW motor & 3rd was to make the rear of boat 10ft & front 2? :D

What on earth are they using to make the belt units that heavy? Looks like they're showing something that will work just fine on the steam paddle wheels on the mighty mississippi.

Will try to get by GTO over at Ocala next few days sense they closest dealer just see what they say.

Not ready to chunk anchor just yet tho sense the shorter belt will surely bring engine level down to somewhere I might be able to manage. Also sense I don't eat at Subway I'm abt 100lbs over weight so with a heavy motor up high everything else is really LOST!

Thanx Gben
 
Norman at GTO will definitely steer you towards a gear box, and I believe with good reason.

One day I'd like to have a gear box (maybe I should get an airboat first huh?) but first I would like to experiment with making a direct drive perform by building for low end torque.

A 350 or 383 with good cylinder heads, cam and exhaust system and fuel injection should work great.
 
Red Dwarf : The problem I encountered with small block chevy's in direct drive applications was the rear main bearing would wear excessively on the side. seems like the prop loads the bearing different than an automotive application does. Now if you want to change the bearings often before they completely fail that may be ok. Just sharing a problem I encountered my solution was a gearbox, no bearing problems since.
 
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