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Can i remove this bit of chassis?
jon200 - 21/11/12 at 02:14 AM

Hey Guys,

I am changing the engine in my Locost but i think a part of the Chassis will be in the way. It is the diagonal from the front right corner of the engine bay to the bulkhead area, sort of across the steering column.

Part R in this picture



I can probably get away with cutting the angle a little if it cant be removed? or can it be fitted to the other side?

britishtrident - 21/11/12 at 08:14 AM

No not without turning your chassis into a wobbly jelly, Chapman originally designed the Lotus Seven chasisis without it but introduced early in the designs history because chassis were flexing and cracking.
The best solution is to replace with three smaller members forming "Y" style brace -- this can be done on both sides.
Some builders using V8 engines do remove it and weld in mirror image of the "Australian mod" short diagonal on the other side of the engine bay.
Other solutions are move it to the other side or make it a bolt in part.

splitrivet - 21/11/12 at 08:58 AM

Ive got mine on the other side. Doesnt the book call for one on each side.
Cheers,
Bob

loggyboy - 21/11/12 at 09:12 AM

Just move it slightly?

The Striker chassis no longer has any diaganols on the upper engine bay.

mark chandler - 21/11/12 at 11:46 AM

Replace with a Y brace or make it removable.

Best if you can repeat on both sides, remove and 2 times Y braces, it is only on this side to suit a cross flow engine BTW

big-vee-twin - 21/11/12 at 11:59 AM

Mine has two short diagonals one either side, as the Australian mod BT refers to.


[img] Steering Column Fitted
Steering Column Fitted [/img]

britishtrident - 21/11/12 at 02:09 PM

quote:
Originally posted by big-vee-twin
Mine has two short diagonals one either side, as the Australian mod BT refers to.


[img] Steering Column Fitted
Steering Column Fitted [/img]



Yes a lot of V8 and slant engined cars are built that way but because it loads J1 and J2 away from a node it throws away a lot of stiffness.

jon200 - 21/11/12 at 02:50 PM

Good job I asked then, I will chop it out then. I will cut it in half and do a smaller triangle either side.

In has the chassis number on it, can I put it elsewhere or does it have to be a specific place?

Jon

adithorp - 21/11/12 at 04:00 PM

quote:
Originally posted by jon200
In has the chassis number on it, can I put it elsewhere or does it have to be a specific place?

Jon


Just has to be on the off-side.

britishtrident - 21/11/12 at 04:23 PM

This is the best way to do it


[img][/img]

jacko - 21/11/12 at 05:24 PM

Engine
Engine

As you can see in this photo MK indy's don't have that part
Jacko

sebastiaan - 21/11/12 at 08:01 PM

quote:
Originally posted by jacko
As you can see in this photo MK indy's don't have that part
Jacko


Correct. I put that very diagonal in mine (as said, it did not have it as standard) and it seems to have improved handling and reduced scuttle shake. All very subjective, I know, but I would see if you could devise some way of putting in an alternative.

britishtrident - 21/11/12 at 08:40 PM

The MK chassis is a bit on the sparse side.

Because it was designed to run small low power engines (Ford 1172cc side valve or if you were lucky an MG XPAG or even richer a 100hp Coventry Climax) Chapman's Seven S1 chassis was even more sparse, actually to modern eyes shockingly sparse. To save both weight and cost Chapman never added any metal that wasn't needed but very early in the production of the Lotus Seven S2 the equivalent diagonal member was added to the frame.

A car that is stiff in torsion is much more responsive to suspension settings, relatively small changes in spring rate or damper settings will tune oversteer/understeer to what is required, it will also be less likely to snap from one handling mode to another on a change of steering input.

jon200 - 22/11/12 at 02:29 AM

quote:
Originally posted by britishtrident
This is the best way to do it


[img][/img]


I like the look of that thanks . how would i weld in new frame work on the underside?

Steve Hignett - 22/11/12 at 07:05 AM

Some pics of modded chassis if you click the link below...

http://locostbuilders.co.uk/viewthread.php?tid=132958

DIY Si - 22/11/12 at 04:24 PM

This is how I did mine back when I was building:

Rescued attachment PROGRESS2.jpg
Rescued attachment PROGRESS2.jpg

Quite a bit of extra room, but still with most of the strength retained, if not improved upon.

Welding it in is best done on all sides, as usual, but doing the return on the forward leg of the Y is quite tight. And given the length of weld holding it in on the upper edge, it may not need it.