Lightweight

[Guest ady]

Can you get different grades of this stuf for different gradesof aluminium of do they try to claim one size fits all.

[Guest ScotMac]

OK...i was able to watch their video. It is a bit like an infomercial, but what it shows is pretty amazing. eg, they punch a hole in a aluminum coke can, fill it w/ hts-2000 (amazing surface tension), let it cool, then try to punch a hole in the area filled w/ hts-2000. The can deforms around the hts-2000, but they can't punch a hole in it.

 

They also claim that "time and vibration" does not affect it. However, they chose their words carefully. ie, "time and vibration" say nothing about whether "flexing" will affect it.

[Guest CaLviNx]

Hi

 

Scotmac : No I am not saying I feel it is (the lumi-weld's end result) too brittle , I am saying I will "weld" certain sections on the chassis as I see fit, and if I Personally feel the need to add any "perceived" bracing I will add it , if it actually needs it might be a bone of contention.

 

My main use for it will be to tidy up overlapped joints by filleting and welding in with flush triangles instead of overlapping, and I intend to use ali "organ" pedals for no other reason than I like them better than overslung Pendulum pedals, and I want to add some aliminium box section around the pedal box area to suit my modification.

 

Everyone will have different ways of doing things and different views on what is strong enough and whats not, thats what makes us individuals.

 

 

Regards

 

Mark

[Guest ScotMac]

Mark, what do you mean by "tidy up". ie, the initial discussion of bonding was about strengthening the chassis. Are you saying that you will mainly be using the welding/brazing for cosmetic purposes?

 

Anyway, in terms of welding/brazing the chassis for strength, it is interesting to note that heat treating of aluminum is done around 1000 deg. However, the later aging of the aluminum is done around 400 deg. So, the main concern w/ the 700 deg brazing w/ alumaweld/hts2000/... is overaging. For aging, the aluminum is held at 400 deg for *several* hours. So, it is a question of how much aging will occur when it is heated to 700 deg for a relatively very short amount of time (for the alumaweld'ing)???

 

Here is a great article on exactly this topic, that re-enforces the fact that we really need to find out the alloy of aluminum that RH is using:

 

http://archive.metalformingmagazine.com/2000/04/Lincoln.pdf

 

-sm

[Guest ScotMac]

Mark, i guess i should clear up what i mean, in terms of strengthening the chassis. I firmly believe that the rivetting of the chassis will be prone to shearing, and will be no where strong enough to handle the rigors of racing the car, let alone provide the torsional rigidity needed/desired for racing. Thus, I am proposing bonding/welding/brazing the *entire* chassis.

 

Yes, i agree that each individual may have different goals/desires for their l/w, and hence just wanted to clear up where i am coming from.

 

Cheers, -sm

[Guest CaLviNx]

Hi

 

Scot; yes I will be in the main tidying up for cosmetic reasons, but in what I decide are critical strength areas I will weld up a bit, if it needs it.

 

If you de-burr your drilled holes you should have no problems, and use a bonding agent without welding.

 

With the addition of lumi-weld in the most critical suspension mounting points and some other areas you should at least piece of mind about the longevity and overall integrity of the chassis, for road use the standard construction methods will suffice.

 

Personally I am not getting my panties in too much of a bunch over it. When my kit arrives I will assess how I will proceed and with what method of construction and in what areas I feel I need if at all to beef up a little if any. I might carry out a few track sessions but in the main I will be using the machine for hard road use.

 

Regards

 

Mark

[Snapperpaul]

An engineer friend of mine is concerned with the strength of the Ally where the front suspension wishbones connect to it. Does the kit have any reinforcement around the mounting holes or even a tube for the bolts to go through?

[Guest nikscott]

I am getting some top hat bushes made for the suspension box section. They will be welded in and will help spread the load. There is a tube through the wishbone bush - haven't checked the thickness yet. If it is to thin it may crush when the bolt is tightened.

[Guest Battery Bill]

I cant see that "Track use" is any harder on components than "Aeroplane" use, and aeroplanes are often Pop rivetted together, Granted thats with the correct Bonding or Jointing compound used.

I know that Joeys car's inner seat belt mounting is much bigger than the main undercarriage mounting on the Tucano aircraft! So perhaps we are possibly "Over engineering" some of our cars

Having said that I would rather "Over" engineer than under. But I think as long as you space your rivets correctly and use Jointing or some sort of bonding agent it would be fine.

[swan]

hi

 

following on from paul:

 

This was my initial thoughts on seeing the car for the first time.

 

The hollow section did not look very robust for the wishbones to connect to.

 

Would it be possible to beef this part up with possibly a steel insert in the section?

 

Just a thought .

 

 

Imagine what the wishbones may do to the mounting section on the car

 

with the constant movement of the suspension.

 

 

 

Swan

[Guest Busa Rush]

interesting reading this

 

 

 

The builder is an experienced engineer and has followed the instructions to

the letter, and thats how RH tell you to mount the diff (I couldnt believe

it either). If you continue to follow their instructions you actually end up

enclosing the diff with rivetted panels on all sides so its impossible to

actually get it back out of the chassis if were ever to fail or need a ratio

change!

 

Chris

 

 

----Original Message-----

From: bike-engined-cars@...

[mailto:bike-engined-cars@...] On Behalf Of Steve Mehew

Sent: 06 November 2005 21:06

To: bike-engined-cars@...

Subject: *SPAM*Re: [bike-engined-cars] Re: Robin Hood Lightweight , Comments

please.

 

 

 

Has the builder forgotten to put some bracing in there or do RH want you to

bolt the diff to sheet metal ????? Can't be right ?????

 

 

----- Original Message -----

From: "Ben Bromilow" <btbromilow@...>

To: <bike-engined-cars@...>

Sent: Sunday, November 06, 2005 9:03 PM

Subject: Re: [bike-engined-cars] Re: Robin Hood Lightweight , Comments

please.

 

 

> Wow. That chassis looks flex-tastic!!!!! And the diff mounting looks like

> it

> would be twisted by even moderate power input...

> Seems strange to have a lightweight chassis resulting in a high

> power-2-weight ratio but in a car where you wouldn't actually be happy to

> use it in anger in case of a prang...

>

> Ben

>

>

> ----- Original Message -----

> From: "Chris Gamlin" <chris@...>

> To: <bike-engined-cars@...>

> Sent: Sunday, November 06, 2005 6:52 PM

> Subject: RE: [bike-engined-cars] Re: Robin Hood Lightweight , Comments

> please.

>

>

>> For those that don't know, the Lightweight is an all ally monocoque

>> chassis

>> so will be a lot lighter than the previous Robin Hoods and at least

>> comparable to a normal Locaterfield chassis in terms of weight, so on

>> paper

>> it is very suitable for a BEC install

>>

>> However, having seen in the flesh a chassis in a fairly advanced state of

>> build it is very concerning to me how weak it appears to be, specifically

>> how weak it seems to be in some of the most important areas like

>> suspension,

>> drivetrain and passenger area. Having reached the stage of almost

>> completing

>> the chassis, the owner of the chassis Ive seen is now of a similar

>> opinion,

>> initially the car was purchased as a potential light weight track / race

>> car

>> but he too now feels that it is not suitable for use on track even with

>> the

>> improvements he planned to make to the chassis (foam sandwich as much as

>> possible, properly bond the panels together as opposed to just rivetting

>> as

>> RH suggest etc).

>>

>> The tub sides and transmission tunnel are all single skin ally of

>> approximately 1.5mm thickness with the top "rail" of the chassis just

>> single

>> thickness ally bent over as 3 sides of a square so not properly boxed. If

>> you imagine most of our cars made with slightly thicker (1.5mm so ?) ally

>> panels but leaving the steel ladder chassis on the shelf and you honestly

>> won't be too far away. There are no box sections running along the

>> chassis

>> and the chassis sides appear to offer very little side impact protection

>> and

>> little rigidity, I would guess that with a decent right boot you could

>> almost kick a side panel in and panel beat it around the drivers upper

>> leg

>> if you felt the need!

>> http://www.auiu24.dsl.pipex.com/RobinHood/IMG_0845.JPG

>>

>> The diff appears to be mounted by bolting it through a flat panel of

>> 1.5mm

>> ally that sits either side of it, again I cant see how it will cope with

>> any

>> serious power output without the diff ripping itself from the mountings.

>> There are top and bottom panels to go on at a later stage than these

>> pictures were taken but no extra box section and no additional pickup

>> points

>> so I can't see them giving huge amounts more strength than can be seen

>> now.

>> http://www.auiu24.dsl.pipex.com/RobinHood/IMG_0838.JPG

>> http://www.auiu24.dsl.pipex.com/RobinHood/IMG_0837.JPG

>>

>> The suspension arms pick up on the bit of 2" box section ally you see at

>> the

>> top of the last two pictures and in the picture below, suspended through

>> 2"

>> squares cut into the ally sheet with no obvious method of accurately

>> locating it to get the geometry accurate without complicated measuring.

>> This

>> is the same on the front and the rear suspension

>> http://www.auiu24.dsl.pipex.com/RobinHood/IMG_0840.JPG

>> The rollhoop (not fitted in the photos) is a cobra style twin hoop

>> arrangement pre welded to a thick strip of steel the full width of the

>> rear

>> bulkhead, this strip I would assume is where the top harness straps would

>> bolt to. In isolation this strip is every bit as strong as a piece of box

>> section steel for mounting harnesses to as found in most other kits, but

>> in

>> turn the strip is just bolted / rivetted through more 1.5mm ally sheet at

>> the top of the rear bulkhead, there doesnt appear to be a structural part

>> of

>> the chassis for it to brace against. Im unsure what the bottom harness

>> bolts

>> for lap straps would fix to as there doesnt appear to be any strucutral

>> members in the tunnel / side panel areas where they would normally locate

>> to.

>>

>> Overall I was quite shocked and would worry about the outcome in the

>> event

>> of even a moderate accident. Also as some of the the fundamental areas

>> appear to be weak, they could in themselves contribute to an accident by

>> failing making an accident more likely, and being made entirely from ally

>> means the chassis structure may be prone to fatique cracking over

>> extended

>> periods so even if its strong enough now, will it stil be strong enough a

>> year or two down the road?

>>

>> Apart from the safety / design concerns, it appears to require a lot of

>> man

>> hours to build which may or may not be a problem but something to be

>> aware

>> of before purchasing. You need to first make up a chipboard chassis jig

>> with

>> wood they supply (so no damp garages or else it will swell up and

>> distort),

>> then you have to do a lot of rivetting, deburring and complex folding

>> (not

>> all panels are pre-bent / pre-drilled). I think the amount of work

>> involved

>> wouldnt be far short of building your own Locost chassis from scratch to

>> be

>> honest, and you will end up with a far more structurally sound and proven

>> car with a Locost, in my opinion.

>>

>> Having said all that, I may be totally wrong and the design may work

>> wonderfully, but having seen many race / track / kit cars before none

>> have

>> sent alarm bells ringing in my head like this did, so purely from a

>> personal

>> gut feeling and my limited understanding of chassis design and materials

>> I

>> certainly wouldnt be happy driving one in anger.

>>

>> Chris

[Guest ScotMac]

Hi,

 

In terms of the front suspension, i really don't like the fact that the coil-over strut is putting EVEN MORE stress on the wishbone attach points. So, instead i am planning on switching it to a inboard design, so that the stress will ALL be on the more interior sections of those square/semi-boxed cross members. Conceptually should be a less stressful design (both for the car and for me!!! ;-), but also is better, in terms of handling, to get the unsprung weight off the wishbones.

 

In terms of those differential pictures, one good thing is that there REALLY appears to be a lot of options, in terms of the space and flexibility necessary to replace the sierra differential w/ something better!!! ;-)

 

However, there really must be some missing boxed reinforcement members to attach the diff to...there REALLY MUST BE!!! Well, there will be on my car, anyway!!! ;-)

 

We should thoroughly verify that they don't exist in the kit (Nik? Pete? Colin?), and then begin designing how we are going to ADD THEM.

 

Use either 6061/7005 or 7075 (depending on whether we want to weld it) aluminum. Fully boxed. We will obviously attach it to that "tin" that the diff is attached to in the pictures, but obviously more attachments are needed. My first thought was to attach it to those other lateral boxed members (that are for the suspension), that way creating a nice square of strength. It will allow all four of the members to combine strength, but will it couple it too much w/ the suspension stress??? Other ideas?? Maybe put a BIG THICK piece of flat aluminum on top of all four of them, and then ALSO attach it to the chassis at the front and back of that differential area???

 

Cheers, -sm

[Guest paul thompson]

I'd question the temperatures mentioned for ally heat treatment. You can melt ally with a good blow torch, 1000 degrees must be old money (F) not metric © or you won't have much of a car left.

Bit suprised about the diff mounting, looks very iffy to me too. Flat plate is very strong in tension but it looks a bit thin to prevent bending and even hole elongation under stress. If it were me I'd put some thicker plate in and bond it.

[Snapperpaul]

Looks like in true Robin Hood style, you guys with the lightweights are doing the R & D and the rest of us will ultimately benifit.

Do you build it as RH intended and if bits fail take it up with them, or do you reinforce for peace of mind and add a bit of weight?

I like very much the idea of the Ally foam , or ally honeycomb sandwich.

One last thought, The Rover Discovery diff has been used in other 7 type cars, smaller and lighter.

I am sure that with the engineering expertise of the club membership all problems will be solved in time and we will end with a unique Ally Monocoque Robin Hood.

[Guest ScotMac]

Yes Paul, fahrenheit...ie, i am not looking for my car to be a puddle in the middle of my garage!!! ;-)

 

Putting a flat plate welded/bonded/alumiwelded to the "tin" is an good idea, but a flat plate will make it more difficult to fasten it to other things for added strength (eg, those lateral suspension square members). ie, it will still be susceptible to torsional stress.