5/16" flex shafts

[Brad Christy]

Andy,

I've got a h34r: project h34r: in the works and need some info..........

I hear that you are planning on introducing 5/16" flexshafts, I would guess primarily for the gas guys. Is this true? If so, in your opinion, or anybody elses for that matter, do you think it would be enough for a gear syncronized twin 90? I was told (by somebody whose opinion I greatly respect) that back in the day, the standard driveline for such a set-up was a 1/2" SOLID shaft. Not do denounce the credibility of the source, but this sounds like ten kinds of OVERKILL. What do you guys think?

Jim Allen?

Thanks. Brad.

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BlackJack Hydros

 

[Speed Jr.]

Im curious, what would be the advantage of running a 5/16" shaft? Are some of the big gassers finding 1/4" not strong enough? Interesting. :huh: Geared Twin 90? Id love to see that run.

Larry

 

[Jim Allen]

Brad,

I use a .250 dia solid drive shaft & 4mm (.1575) dia dowel pins in the universal ball ends. The strut shaft is also .250 dia, hardened & tempered straw color, 0-1 tool steel. I have never broken, bent or twisted any of these parts. I have sheared .125 dia dowel pins, when used for the geared twin.

Jim

 

[Tom Foley]

Jim , I remember you from the pond in Freeport back in 1981 when we used to run there , and Vern as well . I was just beginning with my Drag N Fly at the time . I really admire your work, as I am sure Ed influenced you when you started out .. I was wondering if you have ever tried flex shafts ? I know you make all your own hardware obviously , but they are so simple to deal with . Keep up the good work , nice gallery of trick stuff by the way .

 

[Jim Allen]

Jim , I remember you from the pond in Freeport back in 1981 when we used to run there , and Vern as well . I was just beginning with my Drag N Fly at the time . I really admire your work, as I am sure Ed influenced you when you started out .. I was wondering if you have ever tried flex shafts ? I know you make all your own hardware obviously , but they are so simple to deal with . Keep up the good work , nice gallery of trick stuff by the way .

Tom,

That was really a long time ago & NO; I have never used a flex shaft of any size on any boat. I am still in touch with Vern & Cathy.

Jim

 

[Brad Christy]

Jim,

I intend to use a flex shaft. If I can't find a flex shaft strong enough, my h34r: project h34r: will probably end up being a display model. I'm guessing the 5/16" will be more than enough, seing as how the gass guys are not breaking the 1/4" shafts on a regular basis. I just looked HERE and see that a "high stiffness" 5/16" flexshaft has a torque capacity of 81 in/lb. OK all you techies, how much torque does the average geared twin put out?

BTW, I'm NOT buiding a geared twin. It's just going to be a while before it's done, so I'm layin' it low for now.

Thanks. Brad.

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BlackJack Hydros

 

[Jim Allen]

Brad,

Thats about 3 times (1296 in ozs) more, than the torque of my geared twins, that are geared 1 to 1 (460.8 in ozs).

Jim

 

[ACLazer]

I built a 45 Inch AC Mono that was rigged with a 35cc Gas Engine from SG Racing in Italy. SG Racing in Italy It came equipped from the Factory with a Clutch and a 5/16" Collet set up. I removed the Collet/Clutch and rigged and set it up with a 1/4" Square Drive set up. I have had no concerns with Cables but I did crack 2 solder ferrules where the stub shaft screwed into the ferrule. They were kits from WHH. I really think a Steel ferrule would have helped me eliminate that. Cable and solder joint held up fine though. The engine in stock form produced 10 HP and over 4 Ft Lbs of torque on the Dyno at M&D designs Racing. I did manage to set a new XLS36 Mono SAW Record with it.

Geared 90 Twin would be AWESOME, would love to see that :blink:

Good Luck

 

[Brad Christy]

Jim,

If I read your last comment correctly, according to the S.S. White torque rating page, a high stiffness 1/4" flexshaft, at 672 in/oz capacity, SHOULD be enough for your geared twin, right? Hell even the LOW stiffness 1/4" is good for 480 in/oz. HHHMMMMMM...............

BTW, what prop(s) did you find to work the best for your set-up?

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

 

[Jim Allen]

Brad,

I tried a full blade 2170 with leading edge pitch of 5.625 & a cup pitch of 8.375 (average pitch of 7.000). The cup is measured .250 in from the back edge. With the 26,000 to 28,000 rpm pipes, this propeller becomes a pinwheel instantly. I'm waiting for more geared twins to be built & maybe Prenzka will make some suitable wheels. If not, you know what will have to be done to complete this project.

Jim

 

[Geraghty]

Brad,

I tried a full blade 2170 with leading edge pitch of 5.625 & a cup pitch of 8.375 (average pitch of 7.000). The cup is measured .250 in from the back edge. With the 26,000 to 28,000 rpm pipes, this propeller becomes a pinwheel instantly. I'm waiting for more geared twins to be built & maybe Prenzka will make some suitable wheels. If not, you know what will have to be done to complete this project.

Jim

Jim,Pursue a catalog from Simon Higgens of The Prop Shop in the UK.He probably already has the size props you need.

I don't know if The Prop Shop is on the web but I am sure you can make contact with him through Dave Marles @ Prestwich Models in the UK.

Prestwich Models is on the web.

I went and looked....The Prop Shop is on the web.The info is sparce but it is there.

At one time I had a catalog and application sheet from The Prop Shop and there were a ton of larger props.

Prop Shop props are first class and stonger than hell.

www.britnet.net/propshop/

 

[Brad Christy]

Rod,

What's your weigh-in on the matter at hand?

BTW, I can't get the address for the PropShop to work...........

Andy,

I'm still waiting to hear from you.........

Thanks. Brad.

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BlackJack Hydros

 

[ids987]

Brad,

Try http://www.prop-shop.co.uk

forwards to

http://www.britnett.net/propshop/

Ian

 

[Brad Christy]

Guys,

OK, we've resolved the flexshaft issue (or at least I THINK we have), and it seems we've moved on to props so................

Does anybody know how to decipher the PropShop nomenclature? Is the 7018 a 70mm diameter with a 1.8 pitch/diamter ratio? Or is there no real rhymr or reason to the numbers, like the old ABC props?

Jim,

Until it folded, Did the 2170 seem to load the engine enough, or did the engine want more?

Thanks. Brad.

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[Tim_Duggan]

Brad,

Yes, first two digits are diameter in millimetres and the second two are the pitch ratio. the 5th number is the number of blades. for example a Propshop 6516/3 is a 65mm diameter prop with a pitch ratio of 1.6 and three blades (excellent 90 mono prop that one!)

Tim.

 

[Krusty 181]

Brad , your right with the prop shop numbers 7018 is just what you said

basically i have found they are back the front to Octura , with octura putting the pitch ratio /code in front of the prop diameter(mm)

ie a 2170 (octura i assume) is a 70 mm prop with 2.1 pitch ratio

 

[Jim Allen]

Brad,

The 2170 did not fold up because all the propellers I run are full hard. There was not enough pitch & maybe not enough dia for this setup. Maybe the pitch I used would be okay for oval racing if it was not two bladed. I have some prop shop propellers ,7022-3 & others, but I haven't had a chance to work or test these.

Jim

 

[Geraghty]

Rod,

What's your weigh-in on the matter at hand?

Thanks. Brad.

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BlackJack Hydros

Brad,

I have never made enough power with anything to twist up a .250" flex shaft so I have just been lurking here,reading and enjoying this thread trying to learn something.

I have however in the past used a lot of Prop Shop props.It has been several years since I have talked to Simon Higgens[probably over 10 years ago] but as I recall he had molds for props over 100MM in diameter.I also know you can get Prop Shop props from Simon in full hard heat treat.

Simon got his start in tether boat and "big" scale work boat props.

For years,the "brits" have had steam powered tether boats in the UK that are just brutal on propellers.

I have a 15 year old video tape from the UK that shows some of these steam powered tether boats in action.They are absolutely incredible.

As a sidenote... For you guys in RC boating that think you're tough,8 feet up on a drivers stand.......the guys in model boating who really carry their huevos around in a wheelbarrow,are those UK tether boat dudes.They stand there in their waders with a pipe in their mouth, on the outside of a 50' circle with one of those 20+ pound tether boats going by at over 100MPH,no more than 3' from their knees.

Now,those guys are tough.....In fact they are certifiable lunatics.

Later,Rod

 

[shoboat]

Brad,Jim,and Others,

I order propellers from Simon every few months for my gas customers, let me know

if you need anything I will put it on my next order. Simon also does all his propellers

in Stainless Steel for another 15% up charge. Remember that the Prop Shop prices

are in British Pounds not dollars. I have a order going in soon if you need anything.

BTW,we are having a lot of success with 6516/4 blades on Gas Mono hulls and 6518/4

on Gas Cats. Most of my Prop Shop customers are ordering everything in S.S. these days

and we have had some 115mm propellers in S.S. that look like Jet Ski impellers.

Have Fun Testing,

Mark Sholund

 

[Brad Christy]

Mark,

Let's say, for conversation's sake, you were getting ready to deliver 15-16 HP at 25-30K RPM. What prop(s) would you suggest?

Rod,

I think I've already decided agains the 5/16" shaft. It appears I can get a 1/4" with more than enough "huevos".

Thanks. Brad.

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BlackJack Hydros