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terryhalls
27-May-10, 07:27 AM
Does anyone know what sort of craft this is?55685569

Keith Oakley
27-May-10, 02:03 PM
Don't know but the 500 series numbers are usually Swedish
Keith

curtis5420
27-May-10, 08:41 PM
seen similar craft before, but dont know what it is, all i can say is i would put money on it being almost as old as me, and i was born in 76

Mustang Hovercraft
27-May-10, 10:02 PM
Looks like an early BBV?

firth5731
28-May-10, 12:50 PM
it is a bbv
i have the larger 2+2
that has a honda bike engine and it was sold by a chap called Irving

terryhalls
6-Jul-10, 09:14 AM
it is a bbv
i have the larger 2+2
that has a honda bike engine and it was sold by a chap called Irving


This also has a Honda V4. I am just repairing the tunnel before I rev it up. I have had it up to 10000rpm and the craft still does not lift. Is it in the right gear? I have never seen the gear box left on the engine before. Blades are at about 43 deg.

foster2958
6-Jul-10, 11:32 AM
Most bike engine installations run in top gear as this puts the least torque on transmission components. Try top gear and see if it will pull through, if not take it down a gear.

To be absolutely certain you should check the pulley ratios, and the primary and gearbox ratios of the engine and work out how fast the fan will be turning at max. revs to make sure that the fan blade tip speed doesn't exceed safety/design limits and practical limits dictated by noise.

Kevin

terryhalls
6-Jul-10, 02:41 PM
The 2 pullys seem to be the same. I have looked at the spec of the motor bike it cam from ( VFR 400 ) and 1st gear is 3.307 (13/43) 2nd 2.352 (17/40) 3rd 1.875 (16/30) 4th 1.590 (22/35) 5th 1.434 (23/33) and 6th 1.318 (22/29) The primary reduction is 2.117 (34/72). I have been trying to work around that it says the engine is 60hp @ 12500 rpm. The blades are 5Z.

foster2958
6-Jul-10, 03:13 PM
You'd need to also know the diameter of the fan in order to work out the tip speed. Multiply primary drive x gear ratio x pulley reduction together to get the overall reduction. If your top and bottom pulleys are exactly the same size I suspect that it may possibly be designed to run in 3rd or 4th - top gear would probably run the fan too fast without further reduction to the output shaft speed.

I ran a VFR400 NC24 in a junior craft about 10/11 years ago. The gear ratios were slightly different to those you've quoted, but the primary drive ratio was the same. In an 800mm diameter duct we had a 42:64 reduction from the gearbox output to the fan and ran in either 5th or 6th gear; max power of 60bhp at around 12000rpm sounds about right. 12500rpm in 5th gave a fan speed of 2900rpm for us.

It's an absolute jewel of an engine with gear driven cams - like a mini GP bike - sounds marvellous. I've still got it if anyone is interested.

Kevin

Keith Oakley
6-Jul-10, 03:38 PM
Just a further thought to add to the puzzle. If the 500 series no doesn't relate to it being Swedish perhaps it relates to the short period the HCGB used 500 series nos for F503 formula. ie it would originally have had a 503 engine, not the one it has now. Its possible therefore it has never lifted/raced with the present engine.
Keith

terryhalls
6-Jul-10, 03:41 PM
The fan is 900mm tip to tip. 5698 I have repaired the tunnel as there was some damage from what the last owner said “the blades had broken due to something going into them”. Also I was thinking of adding some elevators to restrict the thrust when I wanted. My last craft was a formula 2 with 2 engines. Would this put too much stress on the tunnel?

terryhalls
6-Jul-10, 03:59 PM
Just a further thought to add to the puzzle. If the 500 series no doesn't relate to it being Swedish perhaps it relates to the short period the HCGB used 500 series nos for F503 formula. ie it would originally have had a 503 engine, not the one it has now. Its possible therefore it has never lifted/raced with the present engine.
Keith
The last owner said it flew untill the blades smashed. It had been repaired then left for 2 years.

terryhalls
6-Jul-10, 04:00 PM
You'd need to also know the diameter of the fan in order to work out the tip speed. Multiply primary drive x gear ratio x pulley reduction together to get the overall reduction. If your top and bottom pulleys are exactly the same size I suspect that it may possibly be designed to run in 3rd or 4th - top gear would probably run the fan too fast without further reduction to the output shaft speed.

I ran a VFR400 NC24 in a junior craft about 10/11 years ago. The gear ratios were slightly different to those you've quoted, but the primary drive ratio was the same. In an 800mm diameter duct we had a 42:64 reduction from the gearbox output to the fan and ran in either 5th or 6th gear; max power of 60bhp at around 12000rpm sounds about right. 12500rpm in 5th gave a fan speed of 2900rpm for us.

It's an absolute jewel of an engine with gear driven cams - like a mini GP bike - sounds marvellous. I've still got it if anyone is interested.

Kevin
The fan is 900mm tip to tip. http://www.hovercraft.org.uk/attachment.php?attachmentid=5698&d=1278430460&thumb=1 (http://www.hovercraft.org.uk/attachment.php?attachmentid=5698&d=1278430460) I have repaired the tunnel as there was some damage from what the last owner said “the blades had broken due to something going into them”. Also I was thinking of adding some elevators to restrict the thrust when I wanted. My last craft was a formula 2 with 2 engines. Would this put too much stress on the tunnel?

foster2958
6-Jul-10, 05:35 PM
The construction regulations suggest that fan tip speeds should be kept below 137m/s to keep noise below the recommended levels, and that 122m/s should be considered the maximum for cruising. On this basis you'd need to run the engine in 2nd gear = 118m/s or 3rd gear = 148m/s (excessive) - this assumes the engine pulley and fan pulley are the same diameter.

Looking at the picture I'd be surprised if it was ever a racer in the UK due to the lack of fan guarding from the rear - flow straighteners would normally be installed too.

An adjustable splitter would be more beneficial to a cruiser to increase lift and reduce thrust at low revs rather than an elevator which would do little to the thrust and only really affects the fore/aft attitude of the craft.

Kevin

Bryan
6-Jul-10, 05:47 PM
That was owned by my father some time ago. It has even completed the Rhone raid. He purchased it from a club of some description.The craft is a BBv2 and was powered by a very tired 503 rotax. The engine was such a dog that a change was needed. At the time we were into racing 4 stroke engines and as they were cheap and easy to install the Honda was an easy choice. I,m sure i still have the wiring diagram for the craft and the book. That engine was very reliable however with he best will in the world my father did suffer with farm yard engineering!!. The craft did work but at the time the skirt material was a bit heavy and the overall weight of the craft a bit much for the integrated system. I Know he still has a full skirt for that craft. There a bit heavy but band new. A small offer should see them in the post.
The engine still has the gear box so to change the fan ratio just change gear. Try the craft in different gears it makes loads of difference. Good Luck.
Oh just looking at the fan set up..... this craft needs a full set of 9 blades to keep the pressure in the plenum as it is so heavy. Its only a cruiser so unlike racers your looking full good lift at low speeds and engine rev,s. I,m sure that 6th gear would spin those blades too fast at a very low pitch making them very inefficient. Put 9 in and use the gear box to find the right pitch and the best performance for your usage.
This craft was never raced but had been scrutinized for hcgb insurance.

terryhalls
6-Jul-10, 06:37 PM
The construction regulations suggest that fan tip speeds should be kept below 137m/s to keep noise below the recommended levels, and that 122m/s should be considered the maximum for cruising. On this basis you'd need to run the engine in 2nd gear = 118m/s or 3rd gear = 148m/s (excessive) - this assumes the engine pulley and fan pulley are the same diameter.

Looking at the picture I'd be surprised if it was ever a racer in the UK due to the lack of fan guarding from the rear - flow straighteners would normally be installed too.

An adjustable splitter would be more beneficial to a cruiser to increase lift and reduce thrust at low revs rather than an elevator which would do little to the thrust and only really affects the fore/aft attitude of the craft.

Kevin
It does have a staighteners. I removed what was left of them on Sunday to repair the duct.

terryhalls
6-Jul-10, 06:46 PM
That was owned by my father some time ago. It has even completed the Rhone raid. He purchased it from a club of some description.The craft is a BBv2 and was powered by a very tired 503 rotax. The engine was such a dog that a change was needed. At the time we were into racing 4 stroke engines and as they were cheap and easy to install the Honda was an easy choice. I,m sure i still have the wiring diagram for the craft and the book. That engine was very reliable however with he best will in the world my father did suffer with farm yard engineering!!. The craft did work but at the time the skirt material was a bit heavy and the overall weight of the craft a bit much for the integrated system. I Know he still has a full skirt for that craft. There a bit heavy but band new. A small offer should see them in the post.
The engine still has the gear box so to change the fan ratio just change gear. Try the craft in different gears it makes loads of difference. Good Luck.
Oh just looking at the fan set up..... this craft needs a full set of 9 blades to keep the pressure in the plenum as it is so heavy. Its only a cruiser so unlike racers your looking full good lift at low speeds and engine rev,s. I,m sure that 6th gear would spin those blades too fast at a very low pitch making them very inefficient. Put 9 in and use the gear box to find the right pitch and the best performance for your usage.
This craft was never raced but had been scrutinized for hcgb insurance.

Thanks for the info, with yours and Kevin's knowledge it gives me a direction to go in, I have not had a hover for years and missed it so snaped this one up. How much for the skirt?

terryhalls
7-Jul-10, 05:26 AM
Thanks for the info, with yours and Kevin's knowledge it gives me a direction to go in, I have not had a hover for years and missed it so snaped this one up. How much for the skirt?

G.

terryhalls
7-Jul-10, 05:32 AM
It does have a staighteners. I removed what was left of them on Sunday to repair the duct.

Where i am in SOuthend there are a lot of cockels and I would like to be able to lift without to much thrust when near the beach. That is why I thought of elevators.

Bryan
7-Jul-10, 05:33 PM
The new skirts i have are a well heavy for your craft but they will do as an odd replacement. So as for a price please PM myself and we,ll do the deal in private. Your air flow straighteners were old white fan blades. They were fairly well decade when we owned it. K & M products do some easy to fit flow straighteners as replacements. This will help to stiffen the duct and make it some where round. As i recall round it isn,t!!.
Slow your fan down and put the nine blades at a high pitch. Then start decreasing the pitch to bring the engine speed up. Change up a gear to start speeding up the fan each time trying the craft for lift. At some point you will come across the optimum setting. Just takes a bit of time.