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Hardtop Locost
jamesalx - 27/10/07 at 12:19 PM

Hi all,

I’m building a hard top version of the Locost and wondered is people could look over me design and let me know what they think.

Key:
Red = Stuff I have moded and added
Cream = Guides just for viewing
Blue = Ali frame for nose cone and rad











MikeRJ - 27/10/07 at 12:31 PM

Adding those door apertures will have severely weakened the structure, and I'm not convinced the roof will have put much back in as you are stressing the "A" pillars in bending, and the roof bars are not straight (thus prone to buckling as they will be in compression).

If the roof structure is going to be made from a substantial section material to also act as a roll cage this might not matter so much, otherwise IMO an extra diagonal on either side would help greatly:



[Edited on 27/10/07 by MikeRJ]

speedyxjs - 27/10/07 at 12:39 PM

Im planning a detatchable hard top but am going to have it attatch to a full roll cage. Might be a stronger idea
But looks good

StevieB - 27/10/07 at 02:32 PM

I was going to suggest the same as speedy - use a fairly standard locost chassis with full roll cage and form your roof around that - it'll be safe and good rigidity.

What engine are your going for though, as the extra weight'll mean you want something a bit more powerful.

thunderace - 27/10/07 at 05:05 PM

take a look dutton done them

Cousin Cleotis - 27/10/07 at 05:17 PM

How about gullwing doors and a T- bar style roll cage?

Paul

jamesalx - 27/10/07 at 05:54 PM

quote:
Originally posted by Cousin Cleotis
How about gullwing doors and a T- bar style roll cage?

Paul


Trouble with gull wings is that if you park in a bay you cant get out

joneh - 27/10/07 at 07:00 PM

How about making the whole roof in grp with the roll bar underneath like a cobra rep?

http://www.pilgrimcars.com/newmag/htop.html

You could make it hinged so the whole roof lifts when you get in and out?

JoelP - 27/10/07 at 07:51 PM

i like the look of your design a lot, its similar to something ive considered, a locost with a hot rod style look in the screen. The door apetures wont weaken it from a standard locost chassis since nothing is missing, however, i would recommend a good cage anyway!

jamesalx - 27/10/07 at 07:58 PM

Thanks JoelP glad you like it.

As for the Roll Cage going to make the hoop out of 25 x 50mm 120g steel I have left over from Scrapheap Challenge Road Show, worked for several tone coming from some leaf springs.

mr henderson - 27/10/07 at 08:07 PM

quote:
Originally posted by jamesalx
worked for several tone coming from some leaf springs.


???

jamesalx - 28/10/07 at 09:31 AM

quote:
Originally posted by mr henderson
???


Well, took part in Scrapheap Challenge Road show. Had to build a potential energy drag racer, no engines, rockets.

So I got 4 leaf springs some Vahaxall Combo Vans. Built a frame out of scrap, some of the previously mentioned metal welded a cross it. One poll though one end of the leaf springs, then bent back on themselves over the other poll about a 1/3 of the way up. Bend them back and you got the power. See pick below:







It all went wrong when at the final hours we could not get hold of the gearing we needed so had to do friction drive. As you can see from the pic. There was just to much power and it kept slipping. But even at what must have been 1/3 of the available power we still make the course. But did not win the competition. It was all made good by meeting my bogging Idols and I’m so going to win next year.

iank - 28/10/07 at 09:57 AM

quote:
Originally posted by JoelP
i like the look of your design a lot, its similar to something ive considered, a locost with a hot rod style look in the screen. The door apetures wont weaken it from a standard locost chassis since nothing is missing, however, i would recommend a good cage anyway!


Nothing missing except the upper rails of the spaceframe between the scuttle the seat panel
Should be possible to strengthen it by beefing up the tunnel to make a backbone TVR/Cobra style.

I'd suggest building a balsa model to see what's going on stiffness wise.

jamesalx - 28/10/07 at 10:41 AM

quote:
Originally posted by iank
I'd suggest building a balsa model to see what's going on stiffness wise.


Yep, thats the plan. End up getting myself covered in modle glue.

JoelP - 28/10/07 at 10:52 AM

quote:
Originally posted by iank
Nothing missing except the upper rails of the spaceframe between the scuttle the seat panel


oops, my bad! I only looked at the side view where the tunnel seems to replace it!

jamesalx - 28/10/07 at 12:20 PM

What do we think of this for a backbone?


Angel Acevedo - 28/10/07 at 02:06 PM

quote:
Originally posted by jamesalx
What do we think of this for a backbone?

Overkill!!

MikeRJ - 28/10/07 at 02:20 PM

quote:
Originally posted by iank
Should be possible to strengthen it by beefing up the tunnel to make a backbone TVR/Cobra style.


Only if the rear end is redesigned for it. Removing the outer rails and just beefing up the tunnel structure will just mean all the bars in the rear bulkhead will be put under lots of bending force.

As the option of adding a structural roof is there, it would be sensible to take advantage of it; could probably made made quite a bit stiffer than a standard locost if properly designed.

jamesalx - 28/10/07 at 02:24 PM

quote:
Originally posted by Angel Acevedo
quote:
Originally posted by jamesalx
What do we think of this for a backbone?

Overkill!!


How about this:


Doug68 - 28/10/07 at 11:46 PM

Firstly this thread is going to be of limited value to you as I don't see anyone volunteering to build you a balsa model or do an FEA analysis of the design and without doing either of the these its kind of pointless "imagining" where the loads will go IMHO.

Secondly as MikeRJ says, the roof if done properly could add hugely to the stiffness of the car. And could be make much stiffer than a regular locost.

Lastly when you look at stiffening a part of the car like the tunnel you have to consider how the loads are going to get in and out of that area. For example if the connections between the tunnel and suspension and shock mounts are not stiff enough to cope with the increased load then you'll just be bending that part of the frame instead of the tunnel.

[Edited on 29/10/07 by Doug68]