revilla Posted March 1, 2015 Share Posted March 1, 2015 Pete,OK just been out to my lab (garage!) messing around with magnets. I reckon you can find it with a magnet even more easily than my idea above. All you need is reasonably strong but small bar magnet. If you try to move it over the surface of the skin with your fingers, maybe 1mm off the surface, you can feel the magnet strongly skipping over any holes. It just wants to pull to one side of the hole and skips as you slide it along.I just tried with a simple magnet designed to hold notes to a fridge, it was about 10mm across and you'll need a bit smaller to find a smaller hole, but I simulated your setup using an old seat runner as the "chassis rail" and some 2mm aluminium plate as the "skin". You can't miss the bolt holes in the runner through the plate! The magnet just doesn't want to be over one, it pulls strongly to the side. Honestly it finds the hidden holes really easily, and that's just an old fridge magnet.Here you can get 4mm diameter neodymium magnets with a 0.68kg pull in a pack of 10 for £2.58.If you can't "feel" where there is a tapped hole in the underlying chassis through the skin with one of those (if there is one) I'll eat my hat!PS: Put some tape over the skin first, that magnet will pull in fairly strongly and you don't want to scratch or chip the paint.Andrew Link to comment Share on other sites More sharing options...
Smithy77 Posted March 1, 2015 Author Share Posted March 1, 2015 Andrew,That's a really good shout, thanks! Magnets have been ordered.I'm wondering if there might have been a reason why the previous owner didn't fit the mount in the re-build. Has it been known that some chassis didn't have this captive thread present? The car is a 2004 S3 Academy chassis. Link to comment Share on other sites More sharing options...
CharlesElliott Posted March 1, 2015 Share Posted March 1, 2015 Mine is a 2004 (made in 2003) Academy chassis. I just measured it (although the exhaust is on) and I would say 803mm is good. The centres of both holes are about 17mm up from the bottom of the car. If you think that there is a chassis rail along the bottom of the car, and then the boss - from memory, there aren't any other chassis rails in that area, so apart from the bottom rail I'm not sure what else you can hit apart from the edge of the boss. If it wasn't there, I would expect you just to go straight thorough.How high is the hole?Do you have a better steel tape available to check the measurement? I refuse to use those vinyl type tapes as they stretch etc. Link to comment Share on other sites More sharing options...
CharlesElliott Posted March 1, 2015 Share Posted March 1, 2015 From scaling your drawing - although it is hard to judge where the bottom of the car is - it looks like you have drilled about 25mm from the bottom of the car; is that right? If so, I would suggest you are too high.I measured the height of mine by hooking a steel tape under the body and reading off upwards.Difficult to see on this, but you can see that 25mm would be too high. Link to comment Share on other sites More sharing options...
SM25T Posted March 1, 2015 Share Posted March 1, 2015 I thought it looked high from the original pic ? Link to comment Share on other sites More sharing options...
RS2000 Posted March 1, 2015 Share Posted March 1, 2015 I have no idea how big the captive nut is and perhaps I've missed something, but according to your stuck on tape, hasn't the pilot hole been drilled at c. 808mm rather than 803? Link to comment Share on other sites More sharing options...
revilla Posted March 1, 2015 Share Posted March 1, 2015 For what it's worth I have just measured the height of my mounting hole. With the exhaust in place it's hard to measure exactly but I would say it is AT MOST 17mm as suggested by Charles, possibly as little as 15mm. If you have gone in at anything like 25mm you will be too high. Link to comment Share on other sites More sharing options...
Smithy77 Posted March 1, 2015 Author Share Posted March 1, 2015 Hi Charles, thanks for measuring up. I drilled the hole 23mm up - the same as my rear mount is at. When you consider Andrew's tallys with yours it looks like I am too high. Fingers crossed the mount will still cover the hole! I double checked the vinyl tape with a steel tape and it was bang on. I'll have the magnets soon so will have a better idea then.Thanks for all the input :-) Link to comment Share on other sites More sharing options...
Roger Ford Posted March 3, 2015 Share Posted March 3, 2015 That fabric tape is pretty confusing. As RS2000 says, you could be at 808mm, depending on whether 80 cm is at the centre line or the next full line up. Use a proper steel tape measure, preferably not one of the 99p ones from Halfords or your local 99p store. Link to comment Share on other sites More sharing options...
Smithy77 Posted March 3, 2015 Author Share Posted March 3, 2015 Roger, as above ^^ I did double and tripple check the measurement with a steel tape and it was bang on.I think I am too high and was misguided by going by the rear mount for reference (which looks like it is higher than normal). In hindsight I should have asked others to check the height of theirs.The magnets arrived today so hopefully I'll be able to find it and that I wasn't so far out that the mount still covers the first hole! Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted March 3, 2015 Member Share Posted March 3, 2015 Don't worrry about the first hole: you can get nice-looking washers that are bigger than the mount... just put one at each end and it will look as if it were designed that way.Jonathan Link to comment Share on other sites More sharing options...
CharlesElliott Posted March 3, 2015 Share Posted March 3, 2015 Assuming that hole turns out to be at the top end of the boss, I'm pretty sure the mount will completely cover it anyway. Link to comment Share on other sites More sharing options...
simonpa Posted March 3, 2015 Share Posted March 3, 2015 Smiffy - where in Hants are you?Drilling enough rivets from the inside skin is not a big deal and you can then locate and drill a hole from the inside of the car.If you can get to Fleet, we should be able to sort it quite quickly :)Cheers - Simon Link to comment Share on other sites More sharing options...
Smithy77 Posted March 3, 2015 Author Share Posted March 3, 2015 Simonpa, I'm near Southampton so not too far away. Thanks for the offer of a helping hand. I think with the help of the magnets to locate the hole I'm fairly confident I'll find it with my next drill. If not, I might get in touch!I do have an annoying knock form the rear suspension when cornering though. I saw you posted in Revilla's rear knocking thread in the last few days offering some help...are you an expert in finding knockers? Could be an equally good excuse for a meet... Link to comment Share on other sites More sharing options...
revilla Posted March 3, 2015 Share Posted March 3, 2015 @Simponpa, if you are up for playing with knockers and can wait until April to get you hands on them, I'd probably be up for joining you ... quite a treck I know but Pete will confirm I'm plenty mad enough to be up for it! Link to comment Share on other sites More sharing options...
Smithy77 Posted March 3, 2015 Author Share Posted March 3, 2015 A pair of knockers, I'm sure, must be an enticing prospect for Simon....? Link to comment Share on other sites More sharing options...
simonpa Posted March 3, 2015 Share Posted March 3, 2015 Lol - indeed!Smiffy - in the meantime, if you use a bit of stiff wire, you can probably check where the boss is located by poking around through your existing hole.You can see the rear one in this pic - the front is just out of the image, but should be the same configuration:http://www.therollcagepeople.com/picts/DSCN0530.JPG Link to comment Share on other sites More sharing options...
CharlesElliott Posted March 3, 2015 Share Posted March 3, 2015 Yes - and the point with thr front one (like the rear) is that there is nothing around it except the lower chassis rail. So if you hit something, it must be the boss - famous last words! Link to comment Share on other sites More sharing options...
Smithy77 Posted March 3, 2015 Author Share Posted March 3, 2015 Simon, thanks for posting the pic. It is difficult to tell with the resolution of the pic, but if I am looking at the right bit it looks like there are two holes in the location of the mount - one centrally in the bottom chassis rail, and one slightly offset above and to the right by 1cm or so....am I right? Link to comment Share on other sites More sharing options...
CharlesElliott Posted March 3, 2015 Share Posted March 3, 2015 One is probably the seat belt lap mounting (from the inside), the other is the exhaust boss (from the outside). Link to comment Share on other sites More sharing options...
CharlesElliott Posted March 3, 2015 Share Posted March 3, 2015 Sad that I know all this Link to comment Share on other sites More sharing options...
Smithy77 Posted March 3, 2015 Author Share Posted March 3, 2015 I'm guessing the seat belt mounting is the larger hole offset up and to the right of the exhaust mount hole?I'm wondering whether my rear mount has somehow been bolted through the higher hole, if it is at all possible?? Might explain why it is 5-10mm higher than normal... Link to comment Share on other sites More sharing options...
CharlesElliott Posted March 3, 2015 Share Posted March 3, 2015 Yes, you are right - and it is certainly possible. My car came back from a repair in exactly that way, but it didn't appeal to my sense of 'rightness' so I drilled out the lower hole and bolted the mount in the right place. From memory, the harness boss is 7/16", the exhaust boss is 5/16". Link to comment Share on other sites More sharing options...
Smithy77 Posted March 4, 2015 Author Share Posted March 4, 2015 Tadaaaaa!http://i75.photobucket.com/albums/i315/pullpete/20150303_201426.jpg....and the original hole is completely covered as hoped! I filled it with some RTV silicon too.Tell you what, the magnet idea worked a treat! It couldn't have been any more conclusive; I could literally mark out the exact circumfrence of the hole. It should be the recommened method to be honest - wouldn't even need a tape measure.Charles, regarding the rear mount, I checked the bolt used for it and it is the same size as that for the front mount - suggesting it probably is in the correct boss?Thanks to all! Link to comment Share on other sites More sharing options...
SM25T Posted March 4, 2015 Share Posted March 4, 2015 Excellent news Link to comment Share on other sites More sharing options...
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