Max's Freestyle buggy Discussion thread.
- Thread starter Mini Mad Max
- Start date
Mini Mad Max
Active member
Thanks for all the comments guys! 
Something about very high yield strength I think. I think i said before, It's made from the steel bar they use in reinforcing concrete in buildings. I will discuss bracing it in some way with him later though, as i agree, It's not a great idea for it to bend! That said, perhaps it bending in an impact isn't such a bad thing. All them 5star euro encap renaults have peel away seat belt fixing mounts to absorb some of the energy in an impact.
That's the goal!!! It's been 4 years since i first went to Stoneleigh and i made the mistake of saying "I'll be here in it next year" I could convoy down with you and make sure you don't forget you have a trailer on Mary!
Max
I see what you're saying Alan. It may well bend, but i doubt very much that it would snap. Its far from being brittle. My Dad gave some spiel about its properties when we made it, and he has a degree in material science. The words were too complex to rememberPhaeton":1ga1e0hc said:Max,
My concern is that in the event of an accident all that will happen is this bar will bend or worse still snap
Which means you will end getting too friendly with the steering wheel.
Do you have the option to either make the loop lower/smaller so less bending/snapping force or could you add some diagonal bracing going backwards.
Alan...
Something about very high yield strength I think. I think i said before, It's made from the steel bar they use in reinforcing concrete in buildings. I will discuss bracing it in some way with him later though, as i agree, It's not a great idea for it to bend! That said, perhaps it bending in an impact isn't such a bad thing. All them 5star euro encap renaults have peel away seat belt fixing mounts to absorb some of the energy in an impact.Yeah that makes sense. I shall talk about bracing it with my dad later. I will also get some more pictures of it hopefully displaying its construction, position and direction of force from the harness strap in more detail soon.Steves2580":1ga1e0hc said:Excellent progress Max
I have to agree with Alan, the round bar looks too long and will bend or break with less force than an impact would have. We wouldn't want you to be hitting the steering wheel (with your hip, ha ha)!!
Best to put a diagonal in from the back to the upper arrow (rear half) on Alan's edited picture.
Hope that makes sense ???
Keep up the great work and it will be at Stoneleigh!!
Steve ;D
That's the goal!!! It's been 4 years since i first went to Stoneleigh and i made the mistake of saying "I'll be here in it next year"
I could convoy down with you and make sure you don't forget you have a trailer on Mary! Haha! The race is still on! And because our builds have taken us so long, I am now legally old enough to buy or drink the winner's prizejason_l":1ga1e0hc said:Looking good Max.
Think its time i did a little more to mine as well then i guess.....can't have you getting too far ahead now can we. >
Max
Steves2580
New member
Hi Max,
Did dad talk about the molecular structure or metabolic state of the material altering and becoming weaker due to the stresses of welding and forming?
If you normalise the bracket, you would return its malleability and the possibility of it bending and not fracturing on impact. :
Sorry, couldn'd resist giving you some technical speak ;D
I know you like it!!
Steve ;D
Did dad talk about the molecular structure or metabolic state of the material altering and becoming weaker due to the stresses of welding and forming?
If you normalise the bracket, you would return its malleability and the possibility of it bending and not fracturing on impact. :
Sorry, couldn'd resist giving you some technical speak ;D
I know you like it!!
Steve ;D
Mini Mad Max
Active member
Yes, nothing like a bit of technical speak to get me going... :O haha. The welds are not near the bends, and are only done in short runs for that exact reason. That was to try and minimise the risk of the heat affected zone. I may do some tests with the steel we used. I just got your text as well. You smug so and so!! I was busy drawing mechanics diagrams to work out the kind of force exerted on it at speed. And then i will work out how many newtons are involved and model a way of testing it. For example, tie a strap around it and then hang so many people off it
Also if you are worried about the bent metal work hardening and the welds creating areas of stress, then would welding in braces introduce more heat affected zones and stresses in it all?
Max
I was busy drawing mechanics diagrams to work out the kind of force exerted on it at speed. And then i will work out how many newtons are involved and model a way of testing it. For example, tie a strap around it and then hang so many people off it Also if you are worried about the bent metal work hardening and the welds creating areas of stress, then would welding in braces introduce more heat affected zones and stresses in it all?
Max
Steves2580
New member
Very good Max!
And for your next assignment
You are right with more stresses being put in with the extra bracing, but theses stresses are in tension and not shear, therefore strengthening the loop from being forced forward on impact and fracturing near the welds/heat affected zones.
This is ace, talking utter shite, when I'm ment to be working ;D ;D
Steve ;D
And for your next assignment
You are right with more stresses being put in with the extra bracing, but theses stresses are in tension and not shear, therefore strengthening the loop from being forced forward on impact and fracturing near the welds/heat affected zones.
This is ace, talking utter shite, when I'm ment to be working ;D ;D
Steve ;D
Mini Mad Max
Active member
I'm loving this!! I am actually revising physics for my exam on Friday by drawing these free body diagrams Got some more photo's magically too. Definitely did not just leave my revision! Clearer pictures to follow
Max
Got some more photo's magically too. Definitely did not just leave my revision! Clearer pictures to follow Max
Mini Mad Max
Active member
Here are the photos:
This one shows the welds:
The direction of the bar is pointing down towards the 7/16 fixings so they should take the load that they would've done anyway.
Another Closeup:
And then this is what i gather Alan and Steve propose I do.
I did the calculations and these were my findings. In a 50mph (crash (I doubt any faster with a frontal end impact that I would survive) assuming the car decelerates to 0mph in a second. So that is -22(m/s)/s acceleration. So if Force=mass x acceleration, and we take my weight which is 82kg, then 82 x 22 = 1804 Newtons. However the harness strap is at acting at an angle of approx 45degrees to the bar, so I resolved the force horizontally: 1804cos(45) = 1275.6 N. The harness tugs on the bar 80mm above the bend, so 1275.6 x 0.08 = 102 Nm of torque around that bend. Which is quite a lot. Perhaps a web/brace would be a very good idea after all
Max
This one shows the welds:
The direction of the bar is pointing down towards the 7/16 fixings so they should take the load that they would've done anyway.
Another Closeup:
And then this is what i gather Alan and Steve propose I do.
I did the calculations and these were my findings. In a 50mph (crash (I doubt any faster with a frontal end impact that I would survive) assuming the car decelerates to 0mph in a second. So that is -22(m/s)/s acceleration. So if Force=mass x acceleration, and we take my weight which is 82kg, then 82 x 22 = 1804 Newtons. However the harness strap is at acting at an angle of approx 45degrees to the bar, so I resolved the force horizontally: 1804cos(45) = 1275.6 N. The harness tugs on the bar 80mm above the bend, so 1275.6 x 0.08 = 102 Nm of torque around that bend. Which is quite a lot. Perhaps a web/brace would be a very good idea after all
Max
Steves2580
New member
I love simple calculations :
I wouldn't put a web in there, just two diagonal braces made from the same diameter roundbar, running just a little higher than the biggest web you've sketched in
Anyway, you have to finish it first, before you can crash it
Now get some revision done or you'll become teacher and not someone that can do a real job ;D
Steve ;D
I wouldn't put a web in there, just two diagonal braces made from the same diameter roundbar, running just a little higher than the biggest web you've sketched in
Anyway, you have to finish it first, before you can crash it
Now get some revision done or you'll become teacher and not someone that can do a real job ;D
Steve ;D
Mini Mad Max
Active member
My calculations were wrong. I modeled that harness bracket as the one taking all the load. There are 5 other harness fixing points as it's a 6 point harness thus spreading the load more evenly And also, the deceleration would've been much greater. The actual moment about the bend would be about 125Nm.
Dad just came home. I just had a lecture on breaking strength of steel. Mild steel breaks at half the force of the Reinforcing bar construction steel. So I have plenty of confidence that it won't break. Especially considering that the peugeot I drive uses a similar diameter bar but made of standard mild steel for the seatbelt, as do many cars! A brace would still give me more confidence in it though. The rebar is so strong because it hot rolled and is also alloyed with manganese. However, welding it can cause the crystals to delaminate inside which weakens it around the welds a bit.
Hahaa!! I'd rather never finish it than crash it.
Back to revision Careful what you say Steve! I thought teaching was a real job!
Max
And also, the deceleration would've been much greater. The actual moment about the bend would be about 125Nm.Dad just came home. I just had a lecture on breaking strength of steel. Mild steel breaks at half the force of the Reinforcing bar construction steel. So I have plenty of confidence that it won't break. Especially considering that the peugeot I drive uses a similar diameter bar but made of standard mild steel for the seatbelt, as do many cars! A brace would still give me more confidence in it though. The rebar is so strong because it hot rolled and is also alloyed with manganese. However, welding it can cause the crystals to delaminate inside which weakens it around the welds a bit.
Hahaa!! I'd rather never finish it than crash it.
Back to revision
Careful what you say Steve! I thought teaching was a real job! Max
Mini Mad Max
Active member
Ahh okay. I will try and get it to come as high up as possible without interfering with the harness snap hook. Thanks for the suggestions guysPhaeton":22hbkcku said:Steves2580":22hbkcku said:I love simple calculations :
I wouldn't put a web in there, just two diagonal braces made from the same diameter roundbar, running just a little higher than the biggest web you've sketched in
Yep I'm down with that dude....
Alan
Any more are greatly appreciated. I wouldn't want to miss something that could go wrong in future and result in a broken buggy or worse, a broken me! Thankyou!!
Max
Mini Mad Max":o4o0560k said:Hahaa I didn't think of that! This is going off topic now, but do you reckon i should be trying to book a test as soon as possible?
Max
Edit: I'll find out if they have time late summer, but i think you're right. It seems too much of a close shave to test it and allow for the possibility of a re-test followed by dvla inspection and all that faff. The light at the end of the tunnel suddenly got a bit fainter
I've always booked the test in advance of being ready it focusses the mind & makes a deadline that if you don't meet costs you money & as a Yorkshireman that's not something I have to throw away.I would ring the VOSA centre & ask what their waiting time is, then add a week for VOSA Swansea to bugger about with it.
Alan...
Mini Mad Max
Active member
Haha no, don't be silly I reckon it'll take at least another 5 years....
I'm currently at uni, but as soon as i get back for christmas, the race is on to get it finished. My to do list is not as long as i'd thought it would be, but the jobs are a bit time consuming so i will have to be efficient. If it doesn't arrive at Stoneleigh under its own steam next year, I will be very disappointed. Have you got yours working since the cooling issues after the IVA?
Max
I reckon it'll take at least another 5 years.... I'm currently at uni, but as soon as i get back for christmas, the race is on to get it finished. My to do list is not as long as i'd thought it would be, but the jobs are a bit time consuming so i will have to be efficient. If it doesn't arrive at Stoneleigh under its own steam next year, I will be very disappointed. Have you got yours working since the cooling issues after the IVA?
Max
Mini Mad Max
Active member
wagon":1u4h190c said:lol, uni - you should have bags of time then!
nah not really. sort of lost momentum a bit after that little mishap.
might try and dig it out soon and get it fired up for some snow fun
Haha, I wish! My flat mates are not happy with the lack of time spent getting drunk with them! My course is pretty full on.
Get it ready for Stoneleigh and we could convoy down together!
Radar":1u4h190c said:
Exactly! It's for looking at, not for driving!
Yeah, I got my first donor car when I was 13 I think. So it's been 5-6 years now! Long enough for some people to build 5 or 6 kit cars Max