2013 - Turbine powered hydrostatic launch craft

[fowler]

How much fluid went in?
I'd imagine (not exactly sure) it would take a litre or more

Any port up high will bleed it

How is the level gauged?
Is there level marks on the plastic resovour?
The resovour must be at the height set by OEM

If the pump or motor seized or hydrolic locked then u would know about it
Mass destruction would result
Hydrolic oil can't be compressed, no question
So u can image what happens if u dead head a pump

And if u failed to lube it u can imagine what would happen to each tiny piston running minute tolerances

The risk is internal bypass or a Broken shaft
Internal bypass is when the oil escapes around the pistons
Or more correct high pressure oil returns to the low pressure side
It is caused by heavy wear

But if it has internal bypass it will have very high heat

Lastly and very simply it could have a broken input or output shaft
This would usually result in bad noises

To test for internal bypass and more so a broken shaft
Spin each shaft and u should feel slight compression
Just like an engine u should feel each piston though its stroke
But it's of course multi cylender and tiny so it'll be slight

I can't tell u what's wrong with it without listening to it or seeing it

Ultimate question
Was it working when it came out of the machine originally

 

[sp_1989]

The dealer said it will take less than a quart (liter).

I removed the unit from my test config and oriented it with the fill port as the highest point. I turned the pulley by hand again and I heard more fluid bubble in. I added more to the reservoir.

As I continued to turn the pulley by hand, I moved the lever and the output shaft actually started to turn. When I moved the lever the opposite direction, the output shaft turned in the opposite direction also. I think it *MIGHT* be usable after all.

I re-mounted everything and will try it again when I get a chance.

 

[sp_1989]

Yesterday I tried my hydrostat drive unit.

Running the engine at full speed (not sure of rpm), but the hydro input was running 1700 rpm and the output at full lever movement was 800 rpm in each direction.

I think I'll try to see if I can make it work on the kart.

Below is the latest design...

 

[machinist@large]

Yesterday I tried my hydrostat drive unit.

Running the engine at full speed (not sure of rpm), but the hydro input was running 1700 rpm and the output at full lever movement was 800 rpm in each direction.

I think I'll try to see if I can make it work on the kart.

Below is the latest design...

That sounds about right; I wouldn't try to spin the input more than ~2000 rpm if you don't have to. Conversely, try to confirm the pulley sizes for the original motor vs. the stock input pulley, and use that as your ballpark limit.

I wouldn't try to get to crazy trying to increase the output shaft speed; that decrease in RPM from the input to the RPM max output is part of the gear reduction needed by any type of trans. Finding out the ratio will give you the #'s you need to calc. out the rest of the drive system.

 

[sp_1989]

Speed calc

Ok, so using that info, I get this:
Output shaft speed: 800 rpm
Output drive diameter: 2 in
Axle driven dia: 6 in
Axle speed: 267 rpm
Tire dia: 20 in
Speed: 15.86 mph

Seems a little slower than I'd like.
That's with a 1:3 final drive ratio. Could I go with a faster final ratio? Is there a recommended final ratio?

 

[machinist@large]

Ok, so using that info, I get this:
Output shaft speed: 800 rpm
Output drive diameter: 2 in
Axle driven dia: 6 in
Axle speed: 267 rpm
Tire dia: 20 in
Speed: 15.86 mph

Seems a little slower than I'd like.
That's with a 1:3 final drive ratio. Could I go with a faster final ratio? Is there a recommended final ratio?

Now you're catching me out; with a hydro for your primary, I'm not sure how to calc. out what you can get away with for your final ratio's. Anyone else have any answers?

 

[sp_1989]

Build Stated!

I'll have to figure out my drivetrain specifics yet, but in the meantime I started building. I didn't get as far as I wanted the first day due to several interruptions, but at least I got started.

 

[sp_1989]

Build Day 2

Ok, I got quite a bit farther on Friday and cut a bunch of pieces. The part I was most concerned with was the front axle, but I tried to be careful and I think it turned out pretty decent. I went with 10 deg caster and 10 deg on the kingpin angle.

 

[sp_1989]

Stuck with other stuff like mowing, etc...

 

[OzFab]

I know that feeling; I get very little time to work on my project these days, I have to make the most of what time I do get...

 

[sp_1989]

Steering in the right direction

Finally got a little time over the week-end. I was really trying to get to the stage where I could put wheels on it and see how it rolls. It was a mental motivator and I knew that I'd more than likely have to disassemble things again. I wanted to make sure that I tried to be careful and not just slap stuff together. Here are some pictures of the front end steering assembly. I don't have the upper steering support finalized yet, so it's just clamped in place. Makes it hard to sit and see how things are laid out though.

 

[OzFab]

I see a problem already: very little or no ackermann! If you're running a live axle (even if you're not) it could be a problem

 

[sp_1989]

There is SOME ackerman angle there, but I'll have to take a closer look at that. I basically used the angle that was already in the spindles from the donor. It helps that it has a long wheelbase. I'll try to get a better picture next time I get to work on it and try to see where they line up.

Meanwhile, here's pics from Sunday afternoon.

 

[sp_1989]

Ackerman

Here are a couple pics of the ackerman angle. It works out pretty good with the length of this kart.

 

[sp_1989]

Gimme a Brake

Got brakes now. I like that caliper and disk. One odd thing, the brake disk had a keyway, but the neither setscrew was on the keyway. I just have some tape on the axle on each side to keep the key from sliding out. Mfg defect or on purpose?

I also added a hitch on the back. Maybe that's too optimistic...

 

[sp_1989]

Have a seat

Ok, got the seat frame built and installed the seat. The seat seems to sit up a little higher than I was expecting, but it works. The seat has adjustment forward and back.

Now I need to work on the powertrain. I need to scrounge around to find an engine mounting plate, use some tubing, or buy a plate. I also have to figure out how to get the hydrostat mounted. Then I need a sprocket on the hydrostat output, axle sprocket and engine pulley. Just a few things.

 

[landuse]

Yes! Coming along nicely. I like the adjustable seat

 

[sp_1989]

I had a bracket welded on the back for the hydrostat drive, but I had to cut it off and go a different route. I'm now working on a set of sq. tubes that will 'clamp' on so I can adjust them. I don't have a way to make slots to slide the engine and adjust belt tension, so I'll slide the hydrostat unit and hopefully be able to adjust the chain length to work with it.

I had to be creative on attaching the output sprocket on the hydrostat output shaft, but I think I have something that will work. Hopefully I'll get some more pictures up after a little while.

 

[sp_1989]

Frustrating Carburetor

I think I'm inhaling too many fumes from gasoline... whew.

Does anyone have experience with Tecumseh carbs? This is an 8hp HM80 from a snowblower.

I'm trying to get the engine to run and having problems. I went through the carb. a few months ago and cleaned it. Now I'm trying to run the engine to test the throttle linkage. It will start and kinda run with the choke. If I can keep it running a little while, I can reduce the choke. I try adjusting the mixture screws, but they don't seem to make much difference. Then the engine eventually dies. When that happens, the carb leaks gas like crazy. It pours out the intake and elsewhere. Eventually it stops. I've adjusted the float level and I think the engine vibrates so much the float can't shut off the fuel consistently.

 

[sp_1989]

Pictures

Picture of engine/tranny (no drive chain).
Picture of pedals for brakes and throttle.