The "Hitchhiker's Guide" to the Maxi-Stream mod

[Roland Jacques]

ejmeier

that sounds kind of funny, i can picture myself melting props. but i no that cost money and time. and that part sucks.
how did you heat it? i would think you would have to have the pressure pulling, then heat the 4mmscrew with a tourch when the heat transfers it should come out. i think you need to a have fast high heat. but im just guessing. maybe funkster will chime in in. that acid idea sounds good, but wouldn't that take a long time on brass?

thiers not that much to seal with silicone . id use goop instead of silicon. its a good idea.

[Roland Jacques]

any one no what is the defferance bettween the 402 and 802? rpm? the start up power is about the same.

[ejmeier]

I used a candle to heat up the end of the screw. I really don't like the heat thing, there's too many variables, and it seems like its just guesswork.

That, and the parts are really tiny. Have you ever tried to hold on to a tiny plastic propeller that has no gripping surface whatsoever? (And its HOT.) And simulatneously pull on the opposite end holding a screw that is only 4mm dia. Not the most fun thing I can think of. Hard to get a good grip.

But, if all else fails, I may give it another shot, with the continuous pressure like you said. Maybe it was too much heat in both cases. I have a few other ideas I want to try first. I'm gonna try to force it out while cold, but by threading a nut onto the 4mm screw, and having that press against a washer that fits around the insert. Hard to explain.

But dang, if this works out, these Graupner props look really nice. They don't look "cheap" like others do.

[Roland Jacques]

ejmeier
where did you get your 3 and 4 blade graupner propellers.? and are they RH props.

[ejmeier]

I got them here:
http://www.hobby-lobby.com/grboatprop.htm

Just a note, what Graupner calls right hand is actually left, and vice versa. They label it as if the BOAT is looking at the end of the prop, so its reversed what is normal.

The 4 blades only come in LH. I got a nice 50mm 3-blade RH one though. I got some smaller ones too, but I wrecked 'em. If I can ever get these inserts out, I'll let you know how it turns out.

[Ball]

Originally posted by yourfishman
Ball like stone said how about the direction , is yours allways starting in the correct direction? what type prop are you using LH or RH?
is that the same prop you had to sand?

Mine doesnt start up in the same direction everytime. I made a stopper that corrects the direction, if the pump starts up the wrong way.

The "Great Planes 1.5x1.5 Wildcat/Stinger" prop isnt the same one as I started out with. I started out with a more aggressive pitch prop and had to sand it down. I had to sand so much off it to make it start that the GPH dropped a lot. The great planes prop starts up everytime and puts out mad flow.

Im making a 2nd pump so when I ordered the great planes prop, I also ordered a 1.75" Dumas prop to test out. I'll keep everyone posted on how that plays out.

[Roland Jacques]

Thanks for the heads up on the RH / LH deal. that is great to no before i order.
on these 3 blades, props i guess the 35mm will work for sure. the 40mm will be a maybe? and the 50mm will be very hard to start on the 802/ 402. the 901 should turn the 60mm.

is the inserts are brass or SS? i guess brass is only about 15% copper, i forgot but is that close? do you think that would be a problem with only that small suface area exposed and it painted/siliconed/gooped over. do you no what the Graupner shafts are made of?

[Ball]

Here is a pic of the stopper. Its recessed into the housing so its nice and sturdy.

[hahnmeister]

I wouldnt bother with brass. Sooner or later, that silicone will lose its adhesion to the surface and expose the brass...and then you have a nightmare.

FWIW, I am working on an order w/ fun rc (they special ordered the 2035s for me, and are looking for some 3" props for me). On the 901, I used a LH prop...and didnt notice a startup pref for RH or LH. Luck of the draw maybe (or, technically, mine is a Hi-SPec 5000, so maybe there is a technical diff).

[Bug_Power]

Has anyone tried contacting the prop manufacturer? I'm guessing an email to the manufacturer could get some with no brass inserts. I'm sure if you got 20 or 30 props you could get rid of most of them here. They would just have to pull the props out of the assembly line early, or if they are cast then drilled and tapped (not likely) they would just not add the brass insert. I know I've worked with some manufacturers and they are willing to work with hobbiest most of the time. You may have to learn another language or speak engrish.

[billyzbear]

ejmeier, Why don't you press it out. A bolt going through it, a nut on the back and a spacer that is bigger than the metal insert. You may need a spacer on the nut side as well. Then wrench on the bolt. Or drill into it with brill bits. Small at first and keep getting bigger. You would need a nice set of drill bits though.

[Black71gp]

you wil like the dumas 1.75's on the 802 ball i have two on mine and wow... amazing. but starting it is a pain most times.. but onces its going.. i will probaly keep that on as is and make a few with the props you mentions maybe try dual props of those..

[rivan]

Originally posted by ejmeier
I got some 3 and 4 blade graupner propellers, and they look really nice. However, I have already ruined two of them by trying to remove the metal insert.

....stuff deleted

Do you think I could maybe drop the propeller in some muriatic acid and see if it would corrode the insert away and leave the pro
p untouched? Any other ideas?

I am waiting for mine to do the same thing.

I think Funkster said that the hub was aluminum.

You could try drilling these out if you have a small drill press. I haven't tried this yet but I imagine that at some point the heat buildup will cause the hub to separate and spin out. But thats just theory at this point. I bought the 60mm 4 blade gaupner so I am going to be doing this soon.

[Aquaduck]

To remove the brass insert, drill out as much brass as you can, then soak the prop in either ferric chloride or ammonium persulfate. Both of these chemicals are very nasty. They will eat through anything that is not glass, plastic, or titanium. They will stain your clothes. Use gloves, goggles and even better, do it outside. Both of these chemicals will attck copper and some other metals like there's no tomorrow. You will need to heat the chemical and provide some movement by using an air stone. You must use a heavy glass jar if using on a hot plate. An old glass aquarium heater will also work.

In the PCB industry we use this chemical to remove copper from printed circuit boards.

Amonium Persulfate

[rivan]

Originally posted by jmkins
for the diy stirring mod, if you google magnetic stir bars you will find a number of chemical resistant PTFE coated stir bars in various shapes. Crosses, discs, x shaped bars are common and come in a variety of arm lengths.

Just a something to keep in mind if anyone goes through with trying this mod

The discs look good. But you have to buy a pack of 10 at over $100.

I am thinking that you really dont want this thing touching the tank glass for over a year while spinning. Its going to have to be floated above the glass. And then there is the issue of attaching a prop.

[MayoBoy]

Does anyone want to sell their impeller cover/nozzle piece for a MJ1200 ? I want to do some eductor experiments but I cut all my nozzles off...

[ejmeier]

Originally posted by billyzbear
ejmeier, Why don't you press it out. A bolt going through it, a nut on the back and a spacer that is bigger than the metal insert. You may need a spacer on the nut side as well. Then wrench on the bolt.

Yeah, that's exactly what I was trying to explain in my previous post. I'm going to try that later on today/tomorrow. Hopefully it will be pushed out cleanly without damaging the propeller. But the Graupners are one-sided, with the other end being closed, so it will have to pull out from the back side - the bolt can't pass all the way through the prop.

Otherwise, drilling is tricky because there's nothing to grab onto. At any moment it could "grab" and turn into a spinning, slicing, wheel. I tried tighening a bolt tighter and tighter to see if it would eventually loosen the insert, but that didn't work.

But yeah, the inserts look like they are brass to me. The outside of the insert is barbed, so it looks like it may have been pounded in, or maybe just cast in.

Does anyone know if straight muriatic acid would damage the propellers at all? I think they might be nylon. I don't want to go all over the place looking for these other chemicals, need something easy to find - at least for a backup plan.

[ejmeier]

I tried out my cold-removal jig, and it worked! Perfectly I might add.

Dang, that was so easy, I was able to take it out with just a wingnut, hexbolt, and spacer.

Here's the pic of what I used, along with the insert (perfectly extracted) and the "redeemed" propeller.



In a nutshell, you need a 4mm bolt, (preferably with a hex head so you can grab it with a pliers), a 4mm nut, (preferably a wingnut so its easier to turn), and a spacer that is close to the exact ID of the insert. (I used a nylon one, and drilled it out a bit to get pretty close.)

You put the nut and spacer on the bolt about 1/2 way up, then thread the bolt into the propellers insert, and crank on the wingnut until the insert pops out.

Really easy! [IMG]j[/IMG]

[Rothie]

Sorry,Eric.
Could you give an explanation.I don't understand the wingnut and spacer.

[ejmeier]

Originally posted by Rothie
Sorry,Eric.
Could you give an explanation.I don't understand the wingnut and spacer.

First, you thread the bolt into the brass insert in the propeller. (You should already have the nut and spacer about halfway up the bolt.)

The spacer is what takes the insert out. When you thread the wingnut downward, it pushes the spacer downward too - against the propeller. The spacer is sized so that it will butt up against the propellers body, but will fit around the outside of the brass insert.

As you gradually tighten the wingnut down, it keeps pushing harder and harder on the spacer, which is pushing down on the propeller. Meanwhile, the bolt is still threaded into the insert, so it isn't moving anywhere. So the propeller gets pushed down, and the insert stays threaded onto the bolt.

Does that make sense? It helps a lot if you look at the pic above.

[dhnguyen]

The bolt screws into the threaded insert then the spacer is used to push against it as you turn the wingnut. As you turn the wing nut inwards it will push down on the spacer and at the same time the bolt goes up pulling the insert out. Kinda like a brake caliper compress tool

[ejmeier]

BTW - I just tried "freeing" a four-blade Graupner, and it was WAY harder. And, from looking at it, it didn't look glossy like the other props, it was more dull looking. I am almost certain that it is reinforced with carbon fiber. The blades hardly flex at all.

I actually sheared the bolt off on my first try, but got the insert 75% the way out. I was able to break off what I had already removed, and then I rethreaded it (this time with a hardened bolt) and eventually popped the insert. But, like I said, due to the reinforcement, the 4-blade one was MUCH harder and took much more torque to pull free.

[Rothie]

I think I understand now.
d-I will ignore the brake calipers part.That wasn't covered in home ec class back in the sixties!

[dhnguyen]

[jmkins]

If anyone has any extra parts for a mj1200 mod they want to get rid of please PM me.