Project Theseus

[Noll]

Yep, Craig more than covered the specifics there .

I've figured out a good solution to the issue in my case, I'm dumb and didn't consider the fact that I have indirect access to a machine shop through my boss. Going to take the bumpsteer spacers to him and have him machine 3 or 4mm off the bottom face (will measure to figure out a good exact value) to bring the control arm and tie-rod end up a bit while still retaining the majority of the bumpsteer correction. Should solve everything nicely and no wheel spacers required.

[zedfoot]

Can you refer me to a site showing the geometry of this?

[Noll]

Can you refer me to a site showing the geometry of this?

I'm not sure of one with specific numbers offhand, but this thread has good info:

https://forums.hybridz.org/topic/38615-bumpsteer-faq/

Found this diagram too, it doesn't show how the control arm angle affect the steering though.

post-931-144023509445.jpg

[Dr.Diesel]

I found this image and following writeup that is like our Datsun's from a website talking about bump steer. It refers to racing. But its equally important on a street car.

What Is Bump Steer?

Bump steer is a change in the steering angle of the wheel when the wheel is in bump or droop without turning of the steering wheel or lateral movement in the steering rack. This is due to the arc patterns of the wishbones and the steering arm having different radii and start points. The bump steer angle is the difference in angle between that of the wishbone and that of the steering arm shown in the diagram below.


The Purpose Of Bump Steer


Bump steer is highly undesirable within racing especially on tracks or surfaces that contain bumps. If the suspension is constantly transitioning between bump and droop, then a car with bump steer will constantly be shifting the steering angle of the car and will make the front end very unstable at high speeds. The bump steer in the system will affect the precisely designed Ackermann steering geometry and will make the steering more unpredictable for the driver.

Bump steer can provide an advantage to the rear end of a car on a smooth circuit effectively providing “active toe” during cornering. This can be used on a front wheel drive car to produce toe out, when the suspension is in bump, at the rear of the car to encourage oversteer on turn in; removing understeer characteristics.

[Noll]

Got the tank pretty well cleaned up today to start preparing for the epoxy tank sealer that arrived yesterday. the seams are a little ragged, but I'll slather some epoxy on the outside before paint to clean that up a bit as it's only cosmetic.






Then duct-taped over most of the spots that either definitely had pinholes or was pitted enough that it could have tiny ones. I'll go over the outside of the tank with more sealer before paint to to fill in all the pits so I don't end up with a tank with a bunch of thin spots waiting to rust. The areas by the feed/return lines I'll tape up later for reasons stated below.




before I can apply the sealer, though, I have a bit of a problem. Even after the acid bath, the feed and return lines are blocked solid. I tried compressed air, stabbing some mechanics wire down the tubes, etc, but no joy, the wire stops dead. I'm going to try some braided cable on a drill (think bicycle brake cable), but if that doesn't work I suppose I have a few different options:

#1 - cut around the lines and try to clean them outside of the tank, or if that fails make up some new ones from the nicopp line I have and braze, solder, or epoxy them in place.
#2 - block the lines off, tap the drain plug for a 90deg fitting to use as feed, and either use the nearby small vent tube as the return, or make/attach another return nearby.
#3 - go all out and cut/weld a sump into the tank with some 3/8 NPT fittings


So far #2 or #3 seem like the best options, although ending up with the tank (or fittings) hanging down lower than stock seems less than ideal, if only because it'd be visible from the rear of the car most likely. Thoughts? Now is the time for welding on the tank if I want to do any after all.

[Danielz]

Your braided cable idea on a drill might work - you are mimicking a plumbing snake - which might be an alternative if you have one. And if it fits into the lines. Lines are probably blocked with varnish and crud. Stand the tank up and put a bit of drain cleaner or maybe Varsol to soften the blockage? What about sealing up the sending unit opening and trying shop vac suction at the filler opening (after letting the drain cleaner or varsol soak for a couple of days)? Will be interesting to learn what finally works. You continue to do amazing work!! Inspirational!!

[zedfoot]

Search for Gas Tank Renew to see what I had to do when I accidentally plugged the intake tube with POR15. It wasn't all that difficult.

[zedfoot]

WhiteSpeed has a sump on his tank.

[Noll]

Your braided cable idea on a drill might work - you are mimicking a plumbing snake - which might be an alternative if you have one. And if it fits into the lines. Lines are probably blocked with varnish and crud. Stand the tank up and put a bit of drain cleaner or maybe Varsol to soften the blockage? What about sealing up the sending unit opening and trying shop vac suction at the filler opening (after letting the drain cleaner or varsol soak for a couple of days)? Will be interesting to learn what finally works. You continue to do amazing work!! Inspirational!!

Sadly I didn't have an actual plumbing snake, and that was definitely not an option for the 3/16 line. Some sort of solvent poured into the clogged lines might have helped, but i ended up going a different route (see update below). Many thanks! Just pushing on through all the difficulties to finally get this car done as best I can .

Search for Gas Tank Renew to see what I had to do when I accidentally plugged the intake tube with POR15. It wasn't all that difficult.

Oh yeah, you linked me that a little while back when I was contemplating cutting the tank open. I might end up doing similar to what you did, more info in my update below.


---------------------------------

More work done on the tank today. Started by pulling off the return fitting as there was no way I was getting it unclogged and it was wiggling slightly anyway, so would have needed sealing work (and why do that work to just end up with a tiny return line again?).

Compared to the 5/16 return line that goes along the underbelly of the car, a considerable difference:




Whipped up a replica of the fitting in 5/16:




Made two actually, and mocked up a couple possible spots. The ID of the upper vent hose is a perfect slip fit if I wanted to epoxy/braze in the return there, although I don't know that there's really a benefit to doing that over the stock location?
If I don't use it for that I'll at least be sleeving it with some of the 5/16 tubing as it has some pinholes and is generally pretty pitted. Option 3 would be to just block it up as I plan to simplify the venting anyway as seen here:

http://www.zhome.com/Racing/FuelTankVaporLineMod/FuelTankVaporMod.htm

Ok, on to the feed line. With the help of a long stick, a tiny flashlight on a bendy wire, and a lot of effort I was able to grab a pic of the bottom end of it. Looked pretty darn crusty from what I could see, so I removed it (in two parts because of that upper U bend).






Once out, it cleaned up pretty nicely, and was even able to get the clog out from the far end. I'm mildly annoyed that I removed the line to do this now, but there was no way I was going to be able to get it out in-situe without cutting a hole in the bottom of the tank to get at the far end and given what I could see with it in the tank that seemed like a big gamble. Not really going to be able to get it back in, the sender hole is too small to fit a hand in to maneuver it into place (and it's cut in half now so...).

The return line is pretty much sorted then (just need to decide which hole to use), so I pretty much need to figure out what I want to do for the feed, and then epoxy the tank after that's all in place.
Current options I'm pondering:

1 - do similar to what I've seen Eric do and bend up a bit of pipe with a 90deg bend on it that runs into the stock feed line hole, epoxy/braze it in place, and run a rubber hose from that on the inside down to the bottom of the tank. Doing this in 3/8 would be good as it would be the same size as the chassis feed line for future EFI stuff, but I don't have any tooling to flare 3/8 line. I suppose I could experiment with using solder to try to make some sort of bulge at the end for the rubber line to slide over?

2 - go with my previous option of just tapping the drain plug for 3/8 npt and running a 90deg 3/8 fitting off that (I could even weld on some protection around the fitting although I think that would be overkill).

3 - make/weld in a sump. Given that I'd most likely be running a surge tank when I go efi this seems like it would be redundant, would also be more work and I'd need to order in some steel NPT weld fittings which would take time to get here.

[Noll]

Small suspension update. Front bumpsteer spacers machined down 4mm, I now have plenty of clearance between the wheel and tie-rod end. One problem off the list.

[Noll]

Decided I'll use the drain as the feed, so blocked off the old feed, soldered in the replacement return line, and sleeved the top leaky vent tube. If time allows I will coat the tank tomorrow, we'll see though.



Also ordered a 3/8 npt tap and corresponding drill bit, as well as the 90deg fitting and some thread sealant.

[Noll]

Alright, tank is now (hopefully) sealed. Poured the majority of the Caswell tank sealant epoxy inside and sloshed it around for a while, and then once it set for a bit I mixed up the rest and brushed it on the pitted areas of the tank after pulling off the tape. Won't know until it all dries and I can pressure-test, but I'm hopeful that this will have gotten all the pinholes. Worst-case I'll order one of their small epoxy kits and add another coat on the outside where needed.



Once that's all done and tested, time to paint, add the feed fitting, and get it in the car I guess.

[zedfoot]

I'm liking your idea of a fitting on the bottom of the tank. Good to the last drop. Mind sharing exactly what you're using and the source?

[Noll]

I'm liking your idea of a fitting on the bottom of the tank. Good to the last drop. Mind sharing exactly what you're using and the source?

Thanks! Yeah, should work out well with any luck.

List of stuff below, fitting, drill/tap, and thread sealant:

https://www.amazon.ca/gp/product/B00...?ie=UTF8&psc=1

https://www.amazon.ca/gp/product/B01...?ie=UTF8&psc=1

https://www.amazon.ca/gp/product/B0002KKTGS/ref=ppx_yo_dt_b_asin_image_o00_s00?ie=UTF8&psc=1

Easy enough to get a different outlet-size fitting too to mate with stock 5/16 line size etc instead of course if desired.

[zedfoot]

Thanks, Noll . That must be some good thread sealant for that money.