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Post by kiwicanfly on Feb 11, 2013 8:44:10 GMT
Worked yesterday and tonight on the bump steer aspects of the car. Yes I know I keep beating the same drum but without acceptable bump steer figures she wont be let out the garage. I posted details of my castor measurement procedure in the technical section but that setup was a pre-cursor to the bump steer. Reckon I cracked it tonight, I did have concerns that I would have to make modifications to the steering rack assembly until the dude who is assembling Stuarts' Rocket here in NZ gave me the answer. I will do a full write up in the technical section but in a nutshell the procedure involves placing two bars on the disks or hubs and setting them level. And parallel at normal ride height then rechecking this at different suspension extension/compression positions. At each point of measurement a plot is made on a simple graph and the curve of this graph indicates the remedial action required. Initially I simply placed the rack on the mounts and measured the back and front distance of the disks, this showed a large amount of bump but unfortunately I didn't record the results. My first real measurements were made with two hardboard packers under the rack giving a height change of 10mm. When measured I got a range of 10mm out at full compression, 0mm at ride height and 4mm out at full extension. When plotted this gave a curve which indicated the Tie Rods were too long. Lots of head scratching how to solve this but thanks to Pete (Stuarts' builder) the solution to this was to move the steering arms in by mounting the mudguard mounting bracket between the steering arm and upright. I did it with washers adding up to the same thickness. This gave me 7mm out / 1mm in / 0mm. I then changed the height of the rack by placing another packer under it increasing it to 15mm. The result of this was a massive detoration to 20mm out / 1mm out / 3mm in. I took the packer out taking me back to 10mm and added another washer to shorten the tie rods further. This gave me measurements of 2mm out / 1mm in / 1mm out, (there were actually five measurement points used with 2mm being the greatest error) a result I was most pleased with. I will be posting a full write up with the graphs and a link to the paper that describes the procedure in full. It is important to note that the results I obtained apply only to my Rocket, do not replicate without measuring your own setup.
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Post by kiwicanfly on Feb 13, 2013 8:30:29 GMT
Got another box of parts today, this time sailed through customs without grief or duty Can now attach the wheels but came up against a head scratcher. I think I know the answer but I am surprised. I was expecting the rear disk/wheel to be attached similar to the front, ie you bolt the disk onto the hub and the wheel also onto the hub but with different studs. Guess it goes on as one 'package' stud through both disk and wheel. Seems odd but hey I'm a mechanical engineer, not an automotive engineer. Going to make some temporary bushes in place of the rear bearings though as it all has to come apart for powder coating so it will make it easier to handle if I have not pushed the bearings in.
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Post by Deleted on Feb 13, 2013 8:58:07 GMT
Yes, the hub studs do go through the disc, and into the wheel
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Post by kiwicanfly on Feb 13, 2013 9:01:59 GMT
Yeah figured, it just kinda feels ..... well....... rattly, until it's tightened up I mean.
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Post by Deleted on Feb 13, 2013 9:39:20 GMT
Yeah figured, it just kinda feels ..... well....... rattly, until it's tightened up I mean. Being an old ford buff, theres a methos that was used on early fords escorts, especially the front discs. Drill 1 hole through the disc into the hub, 5mm should suffice, remove the disc, drill the disc 5mm to 6mm, and countersink. Tap the 5mm hole to 6mm thread. Replace, and tighten. Maybe do this at 12 and 6 oclock to get a good grip. The only purpose this will achieve, is to secure the disc when the wheel is off. However, once the pads are fitted, and calipers joined up, you may not need this Hence ford leaving it off
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Post by kiwicanfly on Feb 14, 2013 8:05:03 GMT
Ok next dumb question.....
My Hi-Spec rears are tapped, as are my RTR uprights.
Got to frill out the thread in the callipers - Correct?
Have to ask 'cause once it's done too late to find out I shouldn't have!
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Post by Paul (madeye) on Feb 14, 2013 9:51:26 GMT
i mated mine with bith threads and a crush washer. solid.
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Post by kiwicanfly on Feb 14, 2013 12:36:40 GMT
i mated mine with bith threads and a crush washer. solid. Mate, with respect, I was really hoping no-one was going to say that, any torque reading is going to be of the bolt head on the caliper, not of the caiper on the upright.
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Post by kiwicanfly on Feb 15, 2013 8:21:45 GMT
It's a car, It's a car..... well according to my wife if it has a wheel in each corner it's a car. Front wheels went on without grief but I was concerned about the bearing housings in the rear uprights. As I will need to remove the bearings for powder coatings I was not too happy about pushing in the final bearings so I knocked up a couple of dummy bearings at work from acetal. Now the interesting thing was they were cut about 0.002" (0.05mm to you young fellas) below the bearing outside diameter and a similar size oversize on the bore for the hub. But when they were pushed into place they had to be driven in quite hard with a mallet and then the hub was no longer as free running as it was on the bench It is clear that the bearing housing had distorted and shrunk from the heat of welding and, as the heat affected zone was still discoloured, there had been no machining after fabrication, the housing was also no longer round. I am still trying to fathom the SKF chart but the bearing looks like it should have a very slight clearance in the housing, it certainly should not need driving in with brute force. So they will have to be skimmed out at some point so I am quite glad I made up the dummy units. I am also thinking about leaving them in for powder coating to save me having to scrape the powder off before putting the bearings in. Still, ignoring that little issue here is another view ;D Darn it let's look at the wheels. Roll bar is only sat in position at this stage.
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Post by springfield on Feb 15, 2013 9:39:03 GMT
Hello Rob, Keep up the good work, it is coming along nicely. try not to get too bogged down with the technical stuff. What did you expect (Precision!!!!) ? Normally the bearings should be a very slight interference fit, unless otherwise stated. That is to say you can wind them in smoothly and gently in a vise or press with little effort. Otherwise the bearing outer may rotate when it gets hot. Les.
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Post by kiwicanfly on Feb 15, 2013 10:05:27 GMT
Hi Les, I went in thinking it should be a slight interference but I am getting more and more hits showing that a bearing with a stationary housing and rotating shaft should be clearance on the housing and interference on the shaft. I first heard this theory from a guy at work who was studying the subject but I need to check it out a bit more, I will contact SKF next week and get a definitive answer. Tell you what though it should not be the interference it is ! The technical stuff is all part of the fun
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Post by Paul (madeye) on Feb 15, 2013 20:31:36 GMT
i had to press mine rob, and i MEAN press them in, when the first was about half way i knew they were tight, but i was comitted so just pretended everything was ok, as there was very little i could do about it
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Post by springfield on Feb 15, 2013 22:50:04 GMT
Rob, Your mate is correct in saying that a slight clearance or sliding fit is needed on a stationary housing with rotating shaft eg. a fan application. Your hub/housings are going to be far from stationary, they will get a bit of a pounding even before you clock up many miles ( kilometers) I stand corrected on the definitive answer However, deep groove bearings will fail much earlier if they are inserted too tightly as the outer race will affect the ball tolerance. Les.
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Post by kiwicanfly on Feb 15, 2013 23:20:05 GMT
Hi Les, beginning to get the speed wobbles on the bearing fit, I had just considered the stationary issue as relative to the shaft but, yeah she wont half getting pounding ;D Going to see it through though and find out the thoughts of SKF as, stationary or not, it still seems an alien concept to have clearance on either race to be honest and against everything I was taught in good old Derby. However as I have to get them skimmed to size I might as well do it to the correct size
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Post by kiwicanfly on Feb 17, 2013 6:49:33 GMT
Got to put some baffles in my petrol tank tried every way of wriggling out of it no joy Tried introducing aluminium plates through the pump hole but it was not working so today I did this And ended up with this Will have to turn the pump through 90 degrees and baffle for side to side surge but it should do the trick. You can also see in the photo that my pump will be secured with a ring, c/sunk screws and o'ring rather than silicon, means I will be able to remove it easily if required. Also put in some pulleys to redirect my handbrake cable to be central. Got to get me a clevis plate (?), not sure what that bit is actually called where the cable from the handbrake itself attached to the two cables to the calipers so off to the man who knows and see what he has to offer. Would have done more but I was made to go tramping this morning. View from the top - so how is the weather in the UK at the moment
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