View Full Version : Frame design

Nickinoue - n/a
10-Jul-06, 10:23 PM

Just doing a bit of thinking on the engine + fan frame. How have all you designed your frames to optimise the belt tension?

I don’t like the idea of trying to design a frame to a particular belt then having to use shims to make the right tension and was looking for a more flexible design such as the ingenious idea that Andy Collis uses on his frame

http://www.randomorbit.f2s.com/graphics/random_1_eframe4.jpg (http://www.randomorbit.f2s.com/graphics/random_1_eframe4.jpg)

Or use the belt tensioner idea, but was worried this could creatre friction and adds to the belt wear http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif .

What are your thoughts, and what setup do you have?

Thanks, Nick

andycollins - n/a
11-Jul-06, 07:46 AM
Thank for the plug Nick.

I thought it was ingenious at the time too. http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif The idea was not only to make it easy to adjust the tension but also to make it easier to change the belt.

It's true that changing the belt was very quick and easy but as for the tension, well it wasn't really needed. The turnbuckles have to go twice as far as you want the pulley to move (because of the trig of it all) and once set up, thongs don't change so a simple solution will generally be lighter and more reliable.

On version 2 of Random Orbit (one day I'll update the site), I went for shims and packing.

Once you've got things shimmed up there's nothing to stop you measuring the pile of packing and making spacers that are spot on.

Also, the idea of easy belt change on my original frame is still a good one. Think how you will change belts when they do snap and find the simplest, practicable solution.



Nickinoue - n/a
11-Jul-06, 08:17 AM

What im worried about is offsetting the plubber blocks and therefore creating more movement in the bolt which could lead to cyclic fatigue. Is there any pictures that anyone has of their shimmed setup?, just wondered what it actually looks like.

The idea of a quick change belt system would be also a good idea, has anyone got a quick belt change idea they would like to share?

Ill have to weigh up all these factors to see whats best for my craft and i suppose it depends if i wanna race or not but im sure i do! http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_razz.gif .


richardevans - n/a
12-Jul-06, 09:32 AM

http://www.rhevans.co.uk/january2004.htm (www.rhevans.co.uk/january2004.htm)

If I was building my fan frame again I would fix one side of the bearing platform via a pivot, and make the other side adjustable - something like Andy's. Shimming works OK but it is slow to adjust. I'd try and reduce the number of nuts and bolts required to make any adjustment.

Richard E

hover t - n/a
12-Jul-06, 05:35 PM

This pic shows the fan frame setup with belt tensioner on my osprey 5. It seems to work well.

The belt is a polychain GT, 62mm wide it can take 1000hp load I have been told (belt only)

KM products sell the bits for this setup

Trev B

Nickinoue - n/a
13-Jul-06, 12:04 PM
1000 BHP http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif over 30 times the power of ma engine.

Does the belt tensioner allow quick change of the belt system or is it just the same with the added advantage of being able to tension the belt?.

A pivoting pully block sounds like a good idea, i just hope anyone who does this, doesnt experience it coming lose at 10k rm http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif


hover t - n/a
13-Jul-06, 04:40 PM
Hi Nick to change the belt with this setup all u have to do is remove the two nuts on the tensioner and remove it,then the belt can be removed from the pulleys and replaced.

It takes around 10-15 min to change

My engine only revs to 5500rpm so no probs so far.

Trev B