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Learning how to build Lotus Seven replicas...together!
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PostPosted: Tue Aug 20, 2013 6:05 am 
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Hi

anybody tried long trailing arms on live rear axles yet?


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PostPosted: Tue Aug 20, 2013 7:21 am 
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Yes, Ford on the Escorts the most successful 2WD rally car of all time.

Arthur Mallock on the Mallock Specials, one of the most successful Clubman designs of all time.

Use the search function here using Escort, mallock and trailing arms as key words.

Search the internetz for Mallock Trailing Arm Magic.


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PostPosted: Tue Aug 20, 2013 10:10 am 
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As cheapracer posted above + a new design on this site where there is a discussion of that very issue and ultimately a Locost design, which is now under construction:

Car9 Thread ==> viewtopic.php?f=39&t=13810&hilit=Car9

First (?) Car 9 ==> viewtopic.php?f=35&t=14613

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: Tue Aug 20, 2013 10:48 am 
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Long links rule.

Image

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PostPosted: Tue Aug 20, 2013 11:51 am 
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I think I have pictures somewhere at home of a Seven that was delivered from the factory with IRS and long links. I'll try to find them when I get home. Thing is once you start trying to save pictures you get buried with the quantity..

I choose long trailing links for Car9 and I think it's a good choice. We'll see when we get a couple running. It's what I'm used to seeing from running 70's formula cars... Compared to just using wishbones, it spreads the loads out widely into the chassis and also lines the forces up well with where there is strength in the chassis...

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PostPosted: Tue Aug 20, 2013 12:24 pm 
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horizenjob wrote:
I think I have pictures somewhere at home of a Seven that was delivered from the factory with IRS and long links. I'll try to find them when I get home. Thing is once you start trying to save pictures you get buried with the quantity..

I choose long trailing links for Car9 and I think it's a good choice. We'll see when we get a couple running. It's what I'm used to seeing from running 70's formula cars... Compared to just using wishbones, it spreads the loads out widely into the chassis and also lines the forces up well with where there is strength in the chassis...


i remember seeing those myself. but i was looking for more recent feedback. im looking at the original s1 dimensions and they match kei car specs. so if i use a kei car donor and use the smaller s1 specs its a perfect fit. with kei car sized tyres then i get enough space for really long links.

thanks for the replies guys. im looking forward to the car 9 build.


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PostPosted: Tue Aug 20, 2013 6:16 pm 
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On my Legends car, one of the best mods I made has been the longer links. It uses a 3 link, The original lower links were about 18", i increased to 29". I got rid of all the twitchiness on rough surfaces and allowed me to reduce the roll resistance for better compliance over bumps. The short links create a lot of roll steer which is the source of twitchiness as well as severe over or under steer (depending on the angles of the arms). Stiff springs, stiff ARBs and/or high roll centers can be used to limit the roll (there fore roll steer) but that limits performance. Once the links are lengthened, a lot of other components need tuning to take advantage of the long links.


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PostPosted: Tue Aug 20, 2013 7:42 pm 
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All of which makes one wonder: why doesn't everybody use long trailing arms? Answer*: because they encroach on cockpit width.

That's not terribly important for formula cars, but it's significant with the Locost layout.

*Okay, that's not really an answer. It's my best guess, from messing around with long links on paper. If you look on RTz's drawing, you can see where the trailing arms are outside a couple of the chassis diagonals. On a book Locost, the trailing arms are on the same vertical plane as (and behind) the chassis diagonals. And RTz, why aren't those trailing arms parallel? If we've discussed it before, just point me to the topic.

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PostPosted: Tue Aug 20, 2013 8:24 pm 
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JackMcCornack wrote:
Answer*: because they encroach on cockpit width.

...and/or increases the track width. For me it's a combination of both. My frame is 2" wider than a Book and I just BARELY clear. If I were to start over I'd make the frame 1/2" narrower overall.

JackMcCornack wrote:
And RTz, why aren't those trailing arms parallel? If we've discussed it before, just point me to the topic.

I am shooting for an initial 20% anti-squat along with the ability to adjust both the percentage and virtual swing arm length as well as keep the adjusters from becoming overly obnoxious in size. I also want to keep the upper link from climbing unreasonably above the 'door bar' in bump. My picture shows a middle ground of those constraints, albeit without the adjusters.

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PostPosted: Tue Aug 20, 2013 8:48 pm 
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JackMcCornack wrote:
All of which makes one wonder: why doesn't everybody use long trailing arms? Answer*: because they encroach on cockpit width.

That's not terribly important for formula cars, but it's significant with the Locost layout.

*Okay, that's not really an answer. It's my best guess, from messing around with long links on paper. If you look on RTz's drawing, you can see where the trailing arms are outside a couple of the chassis diagonals. On a book Locost, the trailing arms are on the same vertical plane as (and behind) the chassis diagonals. And RTz, why aren't those trailing arms parallel? If we've discussed it before, just point me to the topic.


i was originally planning to bend the links around the back and to the sides of the cockpit. but i think ill just narrow down the cokpit to the original lotus seven s1 width. around 37 inches.

parallel arms bind in roll. check this out: viewtopic.php?f=5&t=13741


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PostPosted: Wed Aug 21, 2013 12:20 am 
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Location: Sunny-Okanagan, Canada, eh?!
Lotus 7-1/2 had long trailing arms.

I can see my fingers getting nasty pinched or sheared off if they were close to the chassis at all.

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PostPosted: Wed Aug 21, 2013 2:09 am 
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flat4 wrote:
parallel arms bind in roll. check this out: http://www.locostusa.com/forums/viewtop ... =5&t=13741
Thanks, that's the one I was looking for. I didn't understand it first time around, but often a pause followed by a second pass improves clarity for me.

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PostPosted: Wed Aug 21, 2013 4:58 am 
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JackMcCornack wrote:
All of which makes one wonder: why doesn't everybody use long trailing arms? Answer*: because they encroach on cockpit width.



That's if you try to go inbetween the chassis and the tyres, otherwise just take the chassis all the way to the tyres and take the links up the inside, works out well.


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