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story and photos by carl heideman
While some people are blessed with mills, lathes and other advanced tools, sometimes the basics …
Do you really want a painted steel bar bearing in plain aluminum block? It will work... for a while.
That's actually the way Lotus designed them for a 7. We were just reproducing them.
So... if it makes it through one race... perfect.
Love the how to, only thing is what about friction? Usually there is a grease channel. Are you gonna drill and tap for a grease fitting and channel?
In reply to aircooled :
You understand the Lotus way.
All Lotus jokes aside, I'll say a little more. On an original 7 like this one, Lotus used the sway bar to triangulate the upper suspension arm, effectively making it an A-arm. Chapman always wanted parts to serve more than one function. So it's a sway bar mount and an A-arm mount. If had a rubber or otherwise pliable bushing, caster would constantly change with compliance of the bushing.
I get that this is like the original, but "Chapman made it" doesn't mean that it can't be readily improved. At least grease it, as StuntmanMike suggested... after all, what's old British car ownership without lots of maintenance tasks and cleaning off of greasy grime?
The use of the sway bar as part of the control arm became pretty common, and it works with a reasonable bushing; of course for a race car something harder than the typical OEM rubber block would be desirable, but there is now this stuff called "polyurethane". ;) There's a rubber bushing between the end of the bar and the lateral arm, right? Why is that okay there - with its resulting compliance - but this mount must be so crude?
Of course, if the part of the hobby that you like is endlessly building replacements for worn parts, then enjoy the time making aluminum shavings and the satisfaction of seeing a nice mounting block emerge. :)
This guy does not speak Lotus. Do those fancy “bushings” weigh more than air? Then no.
BTW that sway bar mount looks a bit overbuilt. You should drill some lightness holes in it until is deforms under load, then subtract one hole.
Aircooled, you totally speak Lotus! Half the fun of a Lotus is how it drives and handles, the other half is the thrill/anticipation of the next parts failure.
So this is my personal Lotus 7. It's pretty original, which is really rare as most of them have been "uprated." I'm not a restoration purist with this car, but I like to keep it pretty original, because plain-jane original 7s are my favorites. It weighs 1115 lbs. A lot of the "uprated" cars weigh in the 1300lb range (and they still break). I actually took off the 13x6 Panasports and fatter tires and went back to steelies and 155R13 tires. My autocross buddies think I'm nuts, but if I want to be competitive, I run a prepped Miata. If I want to have fun and experience old-school driving styles, the Lotus checks that box.
Regarding grease, grease fittings, channel, etc. . I did grease the swaybar mount when I put it on. I can unbolt it and regrease it if/when it needs more. A fitting and channel may work, but may also be stress risers that cause failure. I guess we can have an old fashioned internet debate about that...
In reply to Brian_13 :
Actually, tribologically speaking, steel rubbing on aluminum is not a bad bearing combination (seems to work well on camshafts, eh?)
If you wanted to be AR, you could fit split delrin tophats between the bar and the brackets.
In reply to Carl Heideman :
Carl, I'm going in the same direction with my 7. Skinny Minilites and 155R13s. Which tire brand did you end up going with? Trying to decide between spending the money on the fancy Coker stuff or buying some $30 off brands.. figure I'll probably destroy them hanging the car sideways every chance I get. -Jim
clshore said:In reply to Brian_13 :
Actually, tribologically speaking, steel rubbing on aluminum is not a bad bearing combination (seems to work well on camshafts, eh?)
that's true but take away the oil provided by the engine and it becomes less true.
But personally on something like a swaybar I would probably consider adding grease zerks to it and calling it good. It'll work until it doesn't.
I think some of you are missing that it works - and has worked - in its original application for decades. At this point a delrin bushing would also have needed replaced. The car is what, 50-60 years old? Why try to improve on something that lasted that long?
dculberson said:I think some of you are missing that it works - and has worked - in its original application for decades. At this point a delrin bushing would also have needed replaced. The car is what, 50-60 years old? Why try to improve on something that lasted that long?
Plus, this car is really a restoration that I race sometimes, not a race car. The whole reason I built the bracket was because I was going back to an orginal front suspension setup as the car had an uprated (and heavier) set of front A-arms. I ordered some reproduction brackets from England and they were junk, so I thought, I'll just make my own. And I thought it would make a good story, so I took pictures and wrote it. The intent was to show how to make a simple bracket much more than discuss what works best on a Lotus 7. But we've had some good discussion anyway.
JVL said:In reply to Carl Heideman :
Carl, I'm going in the same direction with my 7. Skinny Minilites and 155R13s. Which tire brand did you end up going with? Trying to decide between spending the money on the fancy Coker stuff or buying some $30 off brands.. figure I'll probably destroy them hanging the car sideways every chance I get. -Jim
I did all of this work 3-4 years ago and at the time Vredesteins were pretty affordable and seemed to have the right amount of sticky. I had them shaved to half tread depth and have been happy with them. It looks like they're not available any more. Tire Rack shows a 185/70R13 with a 160 TW, so they're a little big and there could be a rules issues with the TW depending one how fussy you/your club is.
I figure Lotus 7s were designed for pretty lousy tires and four wheel drifts were part of the driving technique back in the day. We don't drive that way anymore since tires are so much better. So the $30 off brands may be the better option for the "original" experience.
In reply to edizzle89 :
Hmm, OK, but just for grins, lets calculate and compare the max PV of that swaybar/mount vs the PV of the camshaft.
Swaybar:
P = 300 lb (1G load on 1 wheel) x 3/4" width x 1/2" OD = 800 lb/sq in
V = 1/2" OD rotated 20 degrees in 0.1 sec = 0.873 in/sec
PV = 800 x 0.873 = 698
Camshaft:
P = Each 2" OD x .75" wide journal supports 2 cam lobe loads of 250 lb due to spring pressure and valvetrain acceleration @ 6000 RPM/2 = 333 lb/sq in
V = 2" journal diameter @ 3000 RPM = 6.28" x 50 rev/sec = 314 in/sec
PV = 333 x 314 = 157,000
So that is why the camshaft requires continuous oil lubrication to live.
And why the swaybar mount requires no lubrication.
StuntmanMike said:Love the how to, only thing is what about friction? Usually there is a grease channel. Are you gonna drill and tap for a grease fitting and channel?
You do understand that sway bars constantly move up and down. So the first thing that happens is the paint wears off and that provides the needed clearance . As the wear increases you pull it apart and put some anti seieze on the bearing surface it both closes up the excess clearance and allows free movement. The reason you don't grease it, is grease closes up the clearance. That binds the bar. ( ask me how I know that)
Race cars are delicate in this area. Unlike street cars which covers up all that with rubber. You want really close clearance but you have to allow a bit for flex which is what the bars is supposed to do. You can use either aluminum or brass.
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