Thankyou, I was concerned that just a 1/4" stubshaft would severely limit prop selection.
Thankyou, I was concerned that just a 1/4" stubshaft would severely limit prop selection.
I have taken the plunge and purchased the 51" cat hull and will need to wait a few weeks for delivery. A search online has failed to find a 5mm motor shaft to 1/4" flex drive collett, so it seems if I go with a 1/4" flex then I need to use a motor with an 8 mm shaft. I have seen a 40 series with a 6mm shaft designed for helicopter use and a collett is available. Thus if an 8 mm motor shaft is needed then options are a high end TP Power motor (4070) or a 56 series motor.
Is a 1/4" flex essential given the size of the hull (51" X 14.5") or would a quality twin 3/16" flex be adequate please? Two 4082 motors with 45mm props will get the boat into the 60 plus mile per hour range with 6s so I think a 40 series set up should be adequate. I assume the factory uses 3/16" shafts (two piece I believe). This will be a long term project but I feel will be worth the wait.
you can get collets for 8mm motor shaft to either 3/16 shaft or 1/4 inch shaft sizes, maybe the good quality Aeromarine or CC Racing 3/16 flexshafts would be suitable as its not like you building a twin outrigger hydro that asks for long shafts, the cat hulls normally have there motors positioned approx 1/3 rd in from the transom so your shafts would only be about 17 inches long. so its 50 / 50 on shaft size as the price difference if going to 1/4 inch flex is approx $20 plus abit more for strut size difference but not alot i would say. just remember its a big hull and your going to run big powerfull motors.
edit; cc racing flexshafts = 3/16 = $34 and 1/4 = $35. so its $2 more not $20.
Yes, that is what I was thinking, 1/4" is a more sensible option.
If your only going to run a 4070 on 6s, I would go with 187 or 3/16 cable. You don't need 1/4 shaft for that power system. You only need 1/4 shafts if your going to run big 5860 motors size and gas size props.
Mark
so Mark what is the point for those larger 40 series motors to have 8 mm rotor shafts ?
I don't know. Mine has a 5mm shaft but just because another one has an 8mm doesn't mean you need a 1/4 cable. I will be running a 4070 1570kv on 6s in a rigger and I would never put a big 1/4 cable in the boat. And I plan on this boat being an 80 mph boat. My 100mph cat used 3/16 too.
Mark
Mark,
just to clarify, the motor I was looking at the TP Power 4070 (40mm X 100mm) has a nominal 3850 watts with a burst of 7500 watts. Compare to a TPP with a 5 mm shaft, the 4050 (40mm X 83mm), the nominal power is 2350 watts and a burst of 5000 watts. The 4070 is a greatly more powerful motor and perhaps needs the 8 mm shaft.
Compare to a Leopard 4092 with a nominal 2600 watts and a burst 4200 watts.
I don't care how many watts a 4050 to 4070 motor is capable of. I would not use a 1/4 shaft. Period. You will just add drag and more amp draw to the motor unnecessarily.
Mark
Thankyou Mark, as my first "big" boat I am relying on information from those who have done it before and will be guided accordingly. The engineer in me implies the 8 mm shaft on the 4070 is there for a reason otherwise they would have stuck with the common 5 mm shaft.
looks ok to use 3/16 flexshafts with your hull and motor combos but make sure you use a good quality set of shafts like the two brands mentioned also think if your going counter clockwise rotations be sure to use a left and a right direction wound flex shafts not 2 of the same windings.
Many thanks. Definitely going with counter rotating props. I believe that cats spin inwards. With 3/16" flexshafts the issue will be finding a stinger setup big enough. OSE does some nice 3/16" "smart drive" units. I have seen 1/4" drive units the same as on the big Genesis and these looked suitable assuming I was using 1/4" shafts.
"IF" you think you need 1/4 flex! http://mbp-rc.de/collet-clutches-5-x-63-SZK http://www.offshoreelectrics.com/pro...?prod=mbp-1000
Last edited by lars_01; 12-12-2017 at 06:27 AM.
Many thanks, have bookmarked the links.
The 8mm shaft is so it doesn't break or bend as easy in a crash as a 5mm shaft would. But after racing boats for 25 years, I have never broke or bent a 5mm shaft. The shaft size has nothing to do with your cable choice. People asked for 8mm shafts because they were going to abuse the motor past it's limits and felt an 8mm shaft would hold true while being pushed past the motors limits. I would never use a 1/4 cable on a 4070 motor but hey what do I know.
Mark
Mark, many thanks for your experience.
i would say the 8 mm shaft motors were more designed for car use as the off road car motors do take some hard hits on the drive train / gear.
The 8mm shafts are less prone to flexing under high speeds and loads, especially on longer can motors. The clearance between rotor and stator inside is fairly small and the rotor contacting at high rpms will destroy a motor, hence the option of bigger shafts.
NZMPBA 2013, 2016 Open Electric Champion. NZMPBA 2016 P Offshore Champion.
2016 SUHA Q Sport Hydro Hi Points Champion.
BOPMPBC Open Mono, Open Electric Champion.
I understand that 3/16" flexshafts are more than enough for a 40 series motor but given that the hull is 51" then any 3/16" stinger drive is going to look rather anaemic. I wonder if the similarly sized Genesis 1.4 metre had 3/16" or 1/4" shafts. I know that 1/4" drives and stepped down 1/4" flexshafts were an upgrade item for the Genesis to take 3/16" props, however these have an unthreaded stubshaft and a single grubscrew retaining an expensive prop does not inspire confidence.
Perhaps I need to look at 56 series motors to get the beefier looking 1/4" drive stingers.
its worth a thought that when running an offshore type r/c boat that most of the time the prop or props leave the water surface as so the hull of the boat due to the choppy conditions that the model could be running in. so what happens when the prop /s leave the water whilst the motor / s is reving high then the props make contact with the water again and so on ?
there is alot of strain on the drive line and if the drive line is not of a good sound quality , something will eventually break.
look at your 51 inch cat hull for example; this is a big boat and when it is ready to run it is going to be heavy not like a small 30 inch hull which would be half or less weight plus offshore boating conditions are alot different to calm water lake running. so if i was the person building this cat hull for offshore conditions i would consider using 1/4 inch drive gear but for calm water lake running i would go for 3/16 drive gear of good quality.
I am thinking that the 40 series may be replaced by regular sized 56 series and thus 1/4" drives will be used. I need to await the hull and see how much room is available in the sponsons. On the 'factory' boat the stock 4082 motors do look small so space should not be an issue.
I think 40 series motors are a good choice for that hull. It is a dihedral design and handling would benefit from a lighter setup. Dihedral hulls are best ‘up on plane’ and running for maneuvering. Till then they are a bit of a tank.
A 3\16 flex is good for a prop up to 50mm with a good margin of strength. You should be able to find what you are after performance wise within those parameters. I think 1400kv on 6s would be a good choice.
I have 1/4” flexes on a 43” hull with Castle 1717’s(5mm shaft). There is a certain ‘security’ to having the larger shafts and perhaps less maintenance but it is a greater rotational mass with a courser wire within the tube. I bring this part up because I am looking at ways to gain some efficiency on said boat and smaller motors and smaller shafts may be the ticket. The larger motors do seem to like the amps. I did settle on 47mm props.
Just my thoughts, Shawn
PS: it runs good tho https://youtu.be/uuP1Bi1eISk
Wow, the boat is amazing.
40 series were my first choice as the factory set up has twin 4082 with 45mm props and performance at close to 70 mph on 6s is more than adequate for me. My concern is the choice of a stinger for each of the sponsons. I feel a 3/16" stinger would be rather small for a largish hull and that is why I was opting for the 1/4" stingers and consequentially 1/4" flexshafts.
https://forums.offshoreelectrics.com...m%2Fs14948.jpg
https://forums.offshoreelectrics.com...%2F24wsyyu.jpg
does over 125 mph on 10s.
At that speed my reaction time would be about 100 metres too slow.
Well here is where I am thinking to go with stingers http://www.rcboatbitz.com/index.php?...roducts_id=811
You can get these in 3/16” to but I would maybe buy brass bushing(tube) to go to a 3/16 cable. Basically what Speedmaster does.
And look, local to you.
We think alike (I already have the 1/4" Speedmaster rotating bushes purchased for an ill fated project). These are what I was thinking of using. Yes, Joe at RC Boat Bitz is "local". My son has the 3/16" version on his Zonda.
Edit: on rethink, are you suggesting using 3/16" flexshafts in the 1/4" stinger suitably sleeved down to suit?
Perfect, you will have something to reference. You can just use K&S brass to sleeve it. But the bushings wouldhold grease better if you can incorporate one. I am all to familiar with a Zonda. Been picking away at a Fantasm for 4 years.
A word of caution. The Chinese based seller that I purchased my large cat hull from has responded to my query as to why firstly the supplied tracking number was invalid and secondly why it is overdue on delivery. I messaged him as the item was purchased four weeks ago and the delivery maximum time on EMS was expired three days ago.
He advised that while the item was prepared well it was found to be damaged on receipt at the shipping company and returned to the seller. All this happened in the last few days even though the purchase was made four weeks ago and a tracking number supplied at the time. I tried numerous times on the various online tracking companies but the supplied tracking number always returned that no information was available (probably because the item had not been posted??).
The seller has advised that a new hull will be shipped in the next few days and a tracking number supplied. If I had not have already purchased everything to outfit the hull then I would have started a dispute through eBay. As it is, with about $1000.00 in motors, ESC, drivelines, etc., to fit to the hull, I really cannot stop the sale proceeding as I need a hull. Definitely unimpressed that it took the seller four weeks to get the item posted and then did not tell me the item had been returned to him in the last few days as damaged.
This sounds a little suss to me as to why would the shipping company would send back an item that appears to be damaged unless it was squashed total, as opposed to just sending it onto the receiver . i have had damaged goods over the years and never had a parcell / box etc been returned to sender , it arrives at my home damaged. maybe this is true and theres nothing of concern but i would be making sure you have a working tracking number . if you used paypal as payment you should be able to recover any money if things go bad. fingers crossed .
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