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srn4 - n/a
2-May-06, 12:50 PM
Ok, so took the craft for the first flight on a nice flat bit of field...first of all the steering cable mount snaps off..thats an easy fix...so sorted that out..





Went to start it up again and there was a nasty noise from the back...oh dear not good!



On closer inspection it appears that the taperlock bush has snapped allowing the upper pulley to slip back and hit the fan guard



How on earth did the taperlock snap? http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif



I am unbelievably gutted....after all this time I was so close to actualy having fun on this thing..and now its broken http://hovercraft.org.uk/images/icons/smiley_icons/icon_mad.gif



Any thoughts?

KerrinRees - n/a
2-May-06, 02:28 PM
Hi Dunc,



Sorry to hear about this. I have no experience of taper lock fixings. But is the key touching the top (out) face of the the slot in the taper lock bush? If it is surely when the allen screw is tightened there is a huge shear force on the point where it snapped? Doesn't there need to be some clearence to allow the bush to close?



I'm sure someone else will be able to tell if there is a problem there.



P.S when you do find the prob please post it cos I'm using them as well.



Good luck



Kerrin



PPS What is the part number and/or supplier of the taper lock flange, I'm having trouble finding one.

Ta.

Ian Brooks - n/a
2-May-06, 02:31 PM
Hi



Bad luck.... you're at the tap end of the bathtub curve, you just need to look forward to that nice reliable bit in the middle!



Regarding the break - is the key too big? It should be snug circumferentially, but have a little clearance axially (top and bottom). If there is no clearance, that may well cause a high stress in the keyway.



It'll come right in the end....



Cheers

Ian

srn4 - n/a
2-May-06, 02:45 PM
Ian, you may have hit the nail on the head...



Now I have cooled off a bit and looked at the picture again it looks like the taperlock has sheered off where it is sitting on the taperlock...



I will remove a tiny amount of material off the top of the key because Im sure, as you said, the fact that the key is so tight against the taperlock has meant that the taperlock couldnt close properly and has broken....(Oh and order a new taperlock http://hovercraft.org.uk/images/icons/smiley_icons/icon_mad.gif )



Will have to see what happens when I get it back on...



You should have seen peoples faces when I told them that, as a reward for standing around watching instead of getting a ride they WERE going to help me get the hover back onto the trailer http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

Paul Fitz - n/a
2-May-06, 07:26 PM
I am not sure Duncan, but it looks from thephoto that the flange itself is also cracked which might indicate that it is just a little too thin.

srn4 - n/a
2-May-06, 08:07 PM
I dont think the flange is cracked, its just a reflection on the steel...But I will be sure to inspect it all properly before it goes back together!



Dunc

jar2 - n/a
2-May-06, 08:11 PM
Sorry to hear of your problem Dunc,



It will get better (he says - having just fixed a knackered shaft cos some idiot (guess who?) forgot to tighten a bearing retainer screw http://hovercraft.org.uk/images/icons/smiley_icons/icon_eek.gif )



It doesn't look like the taperlok was fully seated - they usually end up flush to the bush or pulley surface - or sometimes a little sunk in. Did you do the tapping with a hammer thing as you tightened up the screws?



A cheap fix to stop the pulley moving on the shaft is to cut a bit of exhaust pipe to fit between the bush and the forward bearing inner shell - it transfers the thrust load directly to the bearing rather than relying on the taperlok or the bearing shaft lock.

srn4 - n/a
2-May-06, 09:14 PM
I actualy suspect that part of the problem is my fault...something to do with the lack of threadlock on the taperlock grub screws allowing them to come loose! (slaps face hard with wet fish!)



I am in the process of going round the entire craft with said product trying to reduce risks in the future!



Dunc

jar2 - n/a
2-May-06, 09:37 PM
Dunc,



You shouldn't need thread lock if you torque the screws up properly. Last suggestion for tonight is to fit the pulley the other way round so the taperlok is on the front side - that way the fan thrust will tighten the lock rather than slacken it (not that it should come loose anyway http://hovercraft.org.uk/images/icons/smiley_icons/icon_smile.gif