Thorjet Fan Conversion - RC Groups
Thread Tools
Jan 17, 2007, 02:24 PM
Dave Appleton

Thorjet Fan Conversion

Hi Guys

To follow on to the increasing number of conversion of units from IC to electric I thought i'd have a bash at converting an all-british unit designed by the Thorpe brothers probably 15 years ago now. The original unit was designed around the micromold impeller designed by Marcus Norman, one of the DF pioneers in the UK. The fans were a modular designed unit of 125mm diameter with a front and rear plate between which were sandwiched the 5 blades. Developments progressed and as motor capacity and power increased so did the fans. Initially the Thorpes added two extra blades to the hub making it 7, to absorb the power of the OS48VX. Obviously for the new breed of larger motors a new blade needed designing, which they did at great cost! The new blade was incorporated into their CNC machined front and back plates and gave a range of fans from 5 through 9 blades, for the most powerful motors in the 91 class.

The subject of this conversion is the 5 blade version of the newer design, pitched at the 67 size motors, which was used on an OS65. Performance was around 10.5lbs at 22,500rpm and speed was about 130mph. I'm unsure what the output of the .65 was in its hey-day, but as a guess-timate I banked on about 3hp, so if I could attain 2.5kw into it, it would provide performance hopefully somewhere close. The rotor is the only component which will carry over as the rest of the unit, while adaptable, is not as light as it could be for EDF use.
Last edited by Fire42; Jan 17, 2007 at 03:01 PM.
Sign up now
to remove ads between posts
Jan 17, 2007, 02:30 PM
Dave Appleton business! item to make is the shroud, which is layed up from 2 layers of 4oz cloth with carbon tows added for strength around the stator mounting area. The plug is hotwired foam, covered in clear packing tape. While it sounds rather rudimentary, it produces a very good shroud and the tape lines are easily rubbed out with wet, wet and dry, leaving a good smooth finish
Last edited by Fire42; Jan 17, 2007 at 02:53 PM.
Jan 17, 2007, 02:38 PM
Registered User
Gordon's Avatar
Originally Posted by Fire42 item ... is the shroud,
No it's not Dave!

First thing should be the choice of motor

Which one will you use, and on what battery?

Best of luck with this project

Jan 17, 2007, 02:43 PM
Dave Appleton up is the motor tube and stator asssembly. The motor I'm using is the Hacker A50-14S, the same as used in Bruffs and my Byro fan conversion. Max RPM is 22k for this motor and max power while quoted at 2kw is obviously good for 2.5+, judging by the success of Bobs conversion. So in theory it should be good for this conversion, as if the fan loads correctly and it'll spin upto 22k for 2.5kw and maybe a tad more, it should kick out a decent amount of thrust. Being an outrunner, routing the wires comfortably over the motor is a concern, so I've molded a small hump in the top of the tube. The fan blows air into a hole in the mount plate, so it is some practical use for cooling. The stators on the original unit are nylon and not long enough anyway, so I had to make my own, based on the geometry of the originals. These are layed up from 1/64 + 1/32 ply with a balsa core, taking about 15 mins each to make and are very reproducable.
Jan 17, 2007, 02:52 PM
Dave Appleton
Gordon...give me a chance will ya!!...hope you are well BTW!

The stators are then bonded to the motor tube in an improvised jig, filleted with microfibre/epoxy mix. Thats where I'm upto so far, will trim stators tomorrow and fit in shroud. I've run the rotor on 10S BTW, but only in the byro shroud I made for my byro conversion, so tip gap was large, but this was only to check the balance. That gave 1600w at about 34v, the pack wasnt fully charged so I'd expect a little more HOC. Also once running in a proper shroud and with tailpipe added and more than likely an additional cell we should be up there.....hopefully

Jan 17, 2007, 03:59 PM
Suspended Account

Strewth, the numbers are building!

So that's me, Gorden, you Dave and a bloke I know who runs a chip shop in East Cheam, all doing high power 120mm edf in the Uk, the numbers are building We will catch up to the yanks and Germans soon.

Ahhhh the heady days of Top Gun in Wesron Zoyland The thorp fan brings it all back! Hey Gordon, do you remember my F16XL with the sequencing gear doors powered by ideas and bits of string? Now that's a model with edf potential.

Great work Dave, still thinking about the model
Last edited by Whistling Watts; Jan 17, 2007 at 04:25 PM. Reason: Nostalga attack
Jan 17, 2007, 04:46 PM
Dave Appleton that you!!!!??

I havent forgotten your pics, will do tomorrow, needed to have motor to hand so couldnt assemble byro unit for pics. Shall do AM tomorrow. Yeah hope this conversion works, should do. I've asked West London Models to ask Hacker about doin a special motor for byro unit. Apparently they've done specials before. Will let you know what they say, should transform the byro unit, or at least put less strain on the system. Must swap numbers at some point.

Keep an eye out on email tomorrow


Jan 18, 2007, 12:15 AM
Suspended Account
Yes, its me, looking forward to it.

Jan 18, 2007, 03:38 PM
Registered User
Sorry to squeeze in here Dave but I would like to say what a fantastic contribution Peter and Paul have made to the world of DF. Genuine, fantastic blokes who have friends and respect all over the world.

PS I know someone who is waiting on a phone call from West London to say that the 94 has arrived.
Jan 18, 2007, 03:43 PM
Dave Appleton
Well I've been pluggin away all day and finished the unit. Went together real nice. Tip gap is 0.5mm max which I'm pleased with. This is only really a test bed for fan and motor so the motor tube will be revised for the next one. Test run maybe later tonight once I mount it to a board. Starting at 10s and going from there.
Jan 18, 2007, 03:45 PM
Dave Appleton
Hi Rob

Squeeze in where you can mate! Would that be you on the receiving end of the DS94 or one Mr Golds??...and WHAT have you in mind for it.?



ps...seen the wyvern yet??
Jan 18, 2007, 06:20 PM
Dave Appleton
Test runs at 10S gave pretty much what I expected, 34v 46A for around 1600w. The shaft on the motor is quite long, but as its returning to the shop next week I couldnt cut it down any before assembling. As a result, although the rotor is well balanced there is a little transitional resonance at about half throttle which clears beyond that. I ran it briefly on 11s and it was smooth with plenty of thrust, though I need to make an adapter plug to fit the wattmeter for this setup. I reckon it will take the full 12S to get up to the desired RPM. Theres also the option of trimming down the 6 blade rotor too, so lots of experimenting to do! The only issue I have with the rotor is the weight which is a modest 7oz, which helps as a flywheel and which I dont need! I cant see where the weight comes from, but I suppose being made of 7 pieces it has to be beefy to hold it together! Looks promising though so I'm pleased thus far

Last edited by Fire42; Jan 18, 2007 at 06:27 PM.
Jan 18, 2007, 06:22 PM
EDF all the way!
bruff's Avatar
What was the RPM?
Jan 18, 2007, 06:45 PM
Dave Appleton
Hi Bob
Havent tach'd it as yet, but aint gonna be more than 17-17.5k at the minute on 10S, simply on the kv maths, assuming 550 will drop to around 500. Like I say 12S will get it up to speed but I suspect it will be a close call on the fan load at 21k. The 'correct' 14S motors are arriving next week so this one's heading back, so trying to get the testing done quickly! It seems to have plenty of power though, will get my tach tomorrow from my folks house and let ya know! My main motivation for trying this at all was to see what the hacker could do, knowing that I wouldnt need more than 22k which is its limit anyhow. If it proves to much at 12S and 21k then I'll just skim a bit off the diameter and go again! For $170 ya cant beat that for a fan motor and its all far more interesting to do than buying something you KNOW will work eh!


Last edited by Fire42; Jan 18, 2007 at 06:52 PM.
Jan 18, 2007, 07:45 PM
Suspended Account
k_sonn's Avatar
Great project Dave. What airframe will you put the fan into?


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Byron glow fan conversion bruff Large EDF Jets 1786 Oct 02, 2016 05:17 PM
Discussion Cermark F-20 Ducted Fan Conversion coloradoz Electric Ducted Fan Jet Talk 14 Nov 21, 2006 05:18 PM
Question 6mm fly rc F-4 Ducted fan conversion DESIGN ENGNR Foamy EDFs 3 Nov 18, 2006 04:33 PM
Discussion GWS A-10 hub fan conversion, not plug and play czechyour6 Foamy EDFs 2 Aug 11, 2006 05:21 PM
Twin Star prop to fan conversion rpm3 Electric Ducted Fan Jet Talk 3 Sep 30, 2001 09:45 AM