Clamshells vs. cycle fenders aero effect?

[Christopher smith]

Does anyone recall any definitve testing that compared lap times or top end? I like the looks of clamshells since that was required back in the 1960s and 1970s in the USA and it kind of stuck with me.

[KnifeySpoony]

Imo, unless you're racing, where laptimes matter, get whatever floats your boat. 

[7Westfield]

No data, but I remember rumor's back in the day that clams made the front end light at racing speeds.

[wemtd]

I think Croc had students put one through a wind tunnel once. Regrettably I don’t recall the results 

[IamScotticus]

I Love clams too but for sport, its better to see where the front wheel is tracking.

I have also heard of the clam tips being forced down.  I can't verify that. 

The Clams give the car that familiar MG TC look that complements the short boot as Lotus marketed the S2 as more of a road car, which carried over to the S4.  This continued with Caterham well into the 80s until Cat introduced the cycles in fiberglass.

I can't think of any Lotus 7 S2 or 3 that had factory cycle wings.  Once Lotus was done banging out alloy noses and fenders of the 6 and S1 Seven, that was it.  GRP was cheaper to make, required less skill set and didn't need painting.   Also,  as these parts tend to get damaged easily,  GRP makes a lot more sense.

 

 

Edited March 28, 2022 by IamScotticus

[Christopher smith]

Thanks---Now I understand why I like that clamshell look. My older brother had a used1949 MG TC which I drove more than he did. That is, until a front spindle broke. He then got a 300SL but my experience with that was limited by very expensive issues with the special injection system. But at 16-18 years old you could not beat the driving experience. Stuck on sports cars ever since.

[11Budlite]

On 3/27/2022 at 10:50 PM, IamScotticus said:

I can't think of any Lotus 7 S2 or 3 that had factory cycle wings.  Once Lotus was done banging out alloy noses and fenders of the 6 and S1 Seven, that was it.  GRP was cheaper to make, required less skill set and didn't need painting.   Also,  as these parts tend to get damaged easily,  GRP makes a lot more sense.

 

 

There were some early Lotus Seven S2 that were available with cycle wings in the UK market.  I don't think they were ever available in the US because we got the clamshells.  This photo showing what they look like is from the Lotus Seven Register Series 2 page.

[IamScotticus]

Thanks Bruce. I hadn't seen this.

[TMRL7]

Awesome picture! 

Things that I recall from my reading/investigation when I began my Seven adventure;  All Lotus Sevens delivered to the USA were considered to be a Lotus Seven America, LHD, clamshell fenders and fully assembled. 

 

Incidentally my car was UK delivery, a kit with clams.  

 

Tim

[DavidL]

As an owner of a 1990 Cat with Clams, although they do flap around a bit, there is no obvious problem with high speed lift at highway speeds (an idicated 80 mph, probably  bit less actual velocity!).

[Christopher smith]

I guess it's just the guys who do flat out racing and I understand they've got enough power to get above 120 mph. Not sure what you do then. There was a rumor that some of the guys lifted the rear end of the clamshells up a little bit for better aerodynamics but got caught by the scrutineers

[John B]

They sure look like they'd create drag and lift, the opposite of what you want on the track. On the street though, who cares. If you like them, by all means get them.

[inchoate]

 

I actually have the cycle fenders that came with my dad's 1962 S2.  He always ran the clamshells as the cycles weren't legal at that time.

 

Not exactly related, but has anyone converted from clams to cycles?  Every now and then I have one too many drinks and start to think that I should get my motor built into a monster, get brooklands screens and cycle fenders.  Not sure how involved the fender swap would be.

[Christopher smith]

Does anyone recall the story details from around 1970-80 era where someone was "caught" raising the rear attachment points for clamshells and SCCA banned that since they were supposed to be a big aero improvement? Seeing so many fast 7s on the track back then, all with clamshells, kind of made me stick with them. My series 1 had already been clamshelled when I picked it up in the UK. It had an Alfa 1300 twin cam before then so the previous owners were not stuck on the originality aspect.

[Bartman]

Hi,

 

I swapped my clams for cycle wings, easy swap just need the mounting brackets and a way to fill the holes left in the side of the car from the bolts that secure the clams, I used dome head bolts and its ok looking.

 

B

[IamScotticus]

Can anyone say if the rear clam wing supports used by Lotus and early Cat improve wing stability at speed?

They are still available at Cat parts.