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The Unofficial all things Jet drive thread

Old 10-07-2011, 05:05 AM
  #4751  
sundogz
 
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Default RE: The Unofficial all things Jet drive thread


ORIGINAL: jezzahealy
I have been looking for a source of gears with 3/3.2MM centres and have had no joy so far. Two brushless motors may be the way to go.
That is what I would do. Then you can use the stock couplers. There is a good choice of motors with 2.3mm shafts available.
Old 12-07-2011, 05:42 AM
  #4752  
jezzahealy
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Default RE: The Unofficial all things Jet drive thread

The Ebayer seller of the NQD drives has failed to supply the missing ramp/grills, and does not appear to be responding to my emails, and I am out of time to post negative feed back on Ebay! Has anyone else had any issues?

Anyway, I am quite happy making the grills, however does anyone have any ideas how I can make a suitable ramps for the intakes? I wish to make them as light and smooth as possible.
Old 12-07-2011, 06:06 AM
  #4753  
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Default RE: The Unofficial all things Jet drive thread

Hello,

Ihave used two brushless motors with one ESC on three or four planes- lower Kv ratings, say 1200Kv. Ihave never had problems although i have heard some experience faulty running (motors not arming or throttling up properly).

Like Isaid I've never had a probem. Iunderstand the route casue is the ESC uses the ?EMI back feed voltage to regulate the timings, with one ESC it cannot regulate 2 EMI feedbacks.


What was your experience with using one ESC and two brushless motors?
Old 01-23-2012, 05:13 AM
  #4754  
jezzahealy
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Default RE: The Unofficial all things Jet drive thread

NQD drive unit.

I have now got two 2040 inrunners and I am in the process of coupling them up. They are 2.3mm shafts so use the standard coupler and have the motor points in the correct place for the holes in the motor mount. However the motor mount holes are so close to the plastic molding I am unable to fit the smallest headed screws in. I have sourced some 2.5mm hex head bolts and their heads are just too big! If I file away some of the moulding I am worried it will weaken the unit and creat more flex, but I cant see an alternative. Any advise?

I ultimately made the ramps from car body filler and all seems well.
Old 01-23-2012, 06:23 AM
  #4755  
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Default RE: The Unofficial all things Jet drive thread

The NQD boats with the Graupner knockoff drives came with a round headed phillips screw. When installed there is still a little clearance from the jet housing. I used some hex-headed screws in one unit and they did contact the housing and had to force them in, but they worked. You're right, you wouldn't want to remove any material there as it would weaken the mount.
Old 02-21-2012, 11:50 AM
  #4756  
ollekurt
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Default RE: The Unofficial all things Jet drive thread

Would a graupner mini jet fit into a Turnigy Taipan/Cobra?

its 38 cm/ 15" long
Old 03-28-2012, 02:36 AM
  #4757  
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Default RE: The Unofficial all things Jet drive thread

Anyone seen this video yet?

[youtube]http://www.youtube.com/watch?v=jOdSAX0gH5k[/youtube]
Old 03-28-2012, 03:08 AM
  #4758  
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Default RE: The Unofficial all things Jet drive thread

yep check out the thread on here thats for the nqd jet sprints and youll see some close up on that boat . it has a 29mm drive in it just look up big22bird
Old 03-28-2012, 03:17 AM
  #4759  
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Default RE: The Unofficial all things Jet drive thread

I'm a pit marshal for 1:1 Jet Sprint boats in Australia and I just love these models. I hope to build up one to race on the 1:1 track at lunch break at the meetings.. Do you have a quick link?

Check out the big boys here! http://www.rctech.net/forum/chat-lou...l#post10524583

I love this thread! Read the lot last night.

I was supprised that Mickieb49 didn't post any updates on his boat hull after that BBY boat raised it's (bigger is better) ugly head! Sorry Randy! It's just MHO.

Any updates Mick?
Old 03-28-2012, 05:14 AM
  #4760  
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Default RE: The Unofficial all things Jet drive thread

ORIGINAL: Tech Head

I'm a pit marshal for 1:1 Jet Sprint boats in Australia and I just love these models. I hope to build up one to race on the 1:1 track at lunch break at the meetings.. Do you have a quick link?
[link=http://www.rcuniverse.com/forum/m_7991409/tm.htm]Click this link [/link] for the the NQD jetboat thread.

ORIGINAL: ollekurt

Would a graupner mini jet fit into a Turnigy Taipan/Cobra?

its 38 cm/ 15'' long
The Graupner mini would be perfect for that Turnigy boat.
Old 03-28-2012, 05:30 AM
  #4761  
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Default RE: The Unofficial all things Jet drive thread

Thanks for the quick link, I appreciate it!
Old 03-28-2012, 06:03 AM
  #4762  
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Default RE: The Unofficial all things Jet drive thread

i have one of micks hull setting in my hobby room . that i still havent had time to touch or even know what i wont to do with yet .

thanks sundogz i got tied up i was about to post that link
Old 03-28-2012, 06:25 AM
  #4763  
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Default RE: The Unofficial all things Jet drive thread

I'm so keen to get these boats in a showcase in Australian Jetboat events, I'm sticking to these threads like glue!

How does the hull look? Does it look true and straight? Any pics?
Old 03-28-2012, 10:14 AM
  #4764  
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Default RE: The Unofficial all things Jet drive thread

You'll find lots of pics in the [link=http://www.rcuniverse.com/forum/m_7991409/tm.htm]NQD Jetboat [/link] thread I linked to earlier.
Old 04-03-2012, 04:38 AM
  #4765  
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Default RE: The Unofficial all things Jet drive thread

Ever since i built my first Balsa wood Rc boat,( which cooked with a 13 dollar chinese no name esc) I have been obsessed with the idea of putting a jet drive into this boat http://www.r2hobbies.com/eng/proddet...bt0452002_codewhich i came across whilst researching.  Needless to say i have now bought it and plan on putting the jet drive from a NQD tear into inside it.
I would greatly appreciate any opinons on how the hull will handle a jet.  Ill be running a turnigy marine 35A esc with  im thinking a 2200kv inrunner. on lipo 3 cell.  Would love your opinions. absolute wealth of knowledge on here.
Old 04-04-2012, 10:57 PM
  #4766  
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Default RE: The Unofficial all things Jet drive thread

Hi there. First post, first boat.

I just received my MHZ No Mercy hull and Scorpion 7050/340 motor. Still waiting on HobbyKing to delivery the 53mm jet drive (MHZknockoff), which should be here next week (gulp!).

Anyway, these are big, big toys (13 HP continuous!) and I'm a little uneasy with my flex-shaft knowledge.

I am assuming that Ican simply go Jet(8mm collet)->1/4" flex shaft->Motor(10mm collet) and call it good... but maybe not? For starters, Ican only find 10mm/.250"couplers in the set screw variety, and I've been told these wear the shaft out much quicker.

Also, do Iactually need a stuffing tube w/ teflon liner since I'm not running the shaft through the hull?Part of me says I don't, and part of me says the flex-shaft needs a tube as a guide so it doesn't whip.

This hull is massive and I'd like to set the motor back at least 12 inches from the jet for a good COG, but thats quite a long shaft to run such power.

Part of me just wants to laser align and use direct coupling, but I'm aware of how quickly that can get stupid.

Thoughts?Ideas?Pitfalls? Idon't want to snap flexes and rip couplings off on my first go. =]
Old 04-04-2012, 11:09 PM
  #4767  
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Default RE: The Unofficial all things Jet drive thread

lol... so Ithink my toaster needs some adjusting...

but I couldn't resist. Will start a proper build thread when more parts arrive (and using a proper HD camera).


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Old 04-05-2012, 05:15 AM
  #4768  
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Default RE: The Unofficial all things Jet drive thread

You might want to read [link=http://forums.offshoreelectrics.com/showthread.php?32344-HOBBY-KING-Jet-pump]this review[/link] of the HK jet pump. Seems it has some problems that need to be addressed before use. On the flex shaft, it is not needed. You should use a direct coupler of the flex type (with the silicone or rubber insert). [link=http://www.sdp-si.com/web/html/couplings.htm] These folks [/link] have a good assortment - look up flex couplers in their catalog. Looking forward to seeing your build, Sdg.
Old 04-05-2012, 11:05 AM
  #4769  
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Default RE: The Unofficial all things Jet drive thread

Oh Punisher's thread has been on my favorites for at least a couple of weeks. =] I've already planned for the jet's internal shortcomings and the work that will need to be done to correct them. Unfortunately its the only product in its size class that exists at the moment. I'd kill for a swashdrive but... =/

lol... but honestly Ididn't have a forum membership and couldn't see Punisher's pictures before. Wow! Beautiful work he's done on the mount. The direct water contact is pretty stellar. Perhaps its PM time.

I have access to cnc waterjet/plasma/mill via a friend at Techshop San Francisco (if you've never heard of it, www.techshop.com , every tool on the planet open to the public!) so I might try to do something similar.

He's using a simple jaw coupling of some sourt? I clicked on a few of the coupler types on SDP but didn't see one that matched his. I don't have time this exact second to click every single one. I've actually been meaning to click every possible page on SDP's entire site, just to get a feeling for all of the fun parts that exist in the micro mechanical world. =]

I had hoped to place the motor more towards the center of the boat since the jet + motor are a good 5 lbs together. But, perhaps its unrealistic to do a long coupling in such a torque-drunk application.

I've run twin full size Hamilton 213s in the real world, commercial fishing, and I've long dreamed of using magnetic couplings for that application. I notice SPDP has some but they look pretty wimpy. I wonder if anyone has experience with these?The benefits of the no contact system are said to be numerous, not the least of which is 100% over-power immunity, non-vibration and a huge tolerance for shaft misalignment. In some cases a magnetic coupling can actually be more efficient than direct couplings!

This Australian company is who I've looked at the most: http://www.mgt.com.au/index.php?pageId=6923 and http://www.mgt.com.au/index.php?pageId=6924

But perhaps I'll leave that for the next go round? =]
Old 04-05-2012, 01:00 PM
  #4770  
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Default RE: The Unofficial all things Jet drive thread

Those magnetic couplers are fascinating. [link=http://www.fscoupling.com/4mm-to-5mm-helical-set-screw-flexible-beam-coupling-4x5mm-motor-flexible-coupler-diameter-20mm-length-25mm-p-217.html]Here [/link] is another source for couplers. I used a short piece of flex and two collets to make a coupler in one boat. But I don't see why you couldn't use a teflon lined stuffing tube and put the motor further forward. You would just need to support it.
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Old 04-05-2012, 01:14 PM
  #4771  
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Default RE: The Unofficial all things Jet drive thread

It starting to click a bit more.

Would the stuffing support be like a pillow bearing with the brass actually rotating, or just a static/clamp support with the flex/teflon rotating inside the brass?I assume the latter...
Old 04-05-2012, 01:23 PM
  #4772  
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Default RE: The Unofficial all things Jet drive thread

This looks like a nice coupling for 8-to-10:

http://www.fscoupling.com/8mm-to-10m...-25mm-p-214.ht

Its rated for 19,000 RPM, but my physics knowledge is dusty at best:

2 Newton Meters of torque is about 1.5 foot/lb... which I have no idea how to apply here. (AKA Idon't know the math to figure out if its going to rip in two!)
Old 04-05-2012, 06:29 PM
  #4773  
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Default RE: The Unofficial all things Jet drive thread



ORIGINAL: Heterodox
Would the stuffing support be like a pillow bearing with the brass actually rotating, or just a static/clamp support with the flex/teflon rotating inside the brass? I assume the latter...
Yes, the latter. The stuffing tube will keep the flex from kinking under stress.



ORIGINAL: Heterodox

This looks like a nice coupling for 8-to-10:
Its rated for 19,000 RPM, but my physics knowledge is dusty at best.
The price is certainly right. I don't know what RPM's the HK pump is rated for, but the recommended operational range of my 40mm Powerjet is 10-15K. The smaller units run faster yet. That 19K coupling should handle it fine.
Old 04-05-2012, 08:09 PM
  #4774  
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Default RE: The Unofficial all things Jet drive thread

I'm not sure the HK pump was even designed to spin, much less rated to do it. =p

Joking aside, I'm not sure where else Isaw a 10-15k rpm figure (somewhere on KMB or MHZ Ithink) but Ibelieve that's about where the 49 and 53 mm's sit.

........... Ok, just looked it up... sort of right. MHZ says the 53mm should be linked up their blue line, modded zenoah 26cc orPlettenberg 355/50/5. Zens spin at 17,100 max and Pelttens at 16k, thus I figured 15k would be fine.

The Scorpion 7050/340 will run @ 15,096 RPM on my 12S @ 200 AMP continuous... so that feels about right.

I won't be racing this boat anyhow, so if the HK jet can't be made to sustain those loads I don't mind if I've got a bit of unusuable top end. I mosty wanted to make sure I'd have enough torque available to push the 4-blade impellor and get on step very quickly. Its going to spend 3/4's of its life sitting quietly, waiting to rev wildly. =]
Old 04-06-2012, 05:21 PM
  #4775  
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Default RE: The Unofficial all things Jet drive thread

Has anyone done a build using the new Pro Boat jet drive from the duck decoy retriever? They are cheap and the whole assembly is availble on Horizion Hobby. Just wondering if anyone else has used them yet.

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