AdamR's MX-R1000 Build

Fascinating stuff Adam. Way over my head, but fascinating none the less. Looking forward to the next installment.

Yep enjoying this very much, cracking stuff Ads, keep those updates coming!

Forgive me if I regularly call in to see it taking shape! :)

Welcome any time! Should be making a start on the chassis this week.

Adam,

Excellent stuff as usual. With regards to the tube weld prep, it may be normal to have the profile you have but in my experience in industry if the outer surface is chamfered slightly it would leave what can only be described as a semi knife edged contact leaving a small butted root face to control the throat thickness and strength. That would mean when the weld is completed it becomes ( with a very small gap in the set up) a full penetration weld as opposed to a fillet. This applies mainly in an end to end butt joint. For a 90 degree attachment it would still be a fillet weld but would have greater penetration thickness through the wall of the attached tube for the same leg length of weld. Its probably not important as this type of joint has been made many times but in my game which isn't chassis welding it stands out a little as possibly a weakness or an area for improvement. A fillet being in most cases not as strong as a full pen weld. As I say probably nothing as in the "old days" chassis used to be brazed and also break. Its an excellent idea to have the preps made properly as you are doing which will give greater accuracy of set up and resultant strength. I'm sure with your normal thoroughness you are taking all engineering processes into consideration, it was just a thought any way. Are you going to check any of your welds for potential cracking or are you happy with your welding skills. A DIY crack detection (MPI or DPI) is probably available and isn't necessary on all the welds provided they are all carried out with the same thoroughness as you normally show and should be consistent. 

 

There are plenty of web pages on weld preps and I found the Esab one had a page showing relative stresses versus weld penetration but can't link the page here. Page 35 fig 16.Try this one.

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjuw_e226jJAhXCqQ4KHVKLAGsQFggcMAA&url=http%3A%2F%2Fwww.esabna.com%2Feuweb%2Fsa_handbook%2F585sa2_27.htm&usg=AFQjCNFdaS0KzdwovBuTwXBiF0VKxjfHOQ

 

This may be pure overkill on my part by the way. Or telling granny how to weld tubes whilst sucking eggs..

 

Bob

 

 

 

 

Hey Bob,

 

Thanks a lot for your comments! As you said, I'm a bit of a 'detail sucker' so this is really useful to know... I had intended to chamfer the ends of the 'incoming' tube for the meatier sections to help with penetration, but from what you've said it could be useful throughout. I'm a fan of using engineering methods where possible because, from what I've seen, a lot of 'motosport' stuff in general is sub-standard IMO... I shall have a read through the Esab document - cheers

 

One of the main difficulties I've found with the thin sections I'm using (1.6mm / 1/16") is balancing good penetration while not blowing holes in the tubing, but I think I've got a decent setting now which involves less heat than normal so I can be a bit slower / more controlled with the weld pool. I certainly can't profess to be an expert, but the test joins I did on 1.2mm tube took an almighty battering with a lump hammer before the tubing gave way (rather than the weld), so I'm fairly happy with that.

 

Thanks again for your input, it's always welcome. I always say that every person can learn at least one useful thing from any other person - no exceptions here!

 

Cheers,

Adam

Adam,

Sspot on, the Esab manual actually mentions the preparation thickness for exactly the reason you state. As you say a lot of the "engineering" used has been suck it and see with massive overkill in areas whereas people like Colin Chapman would run with minimal weight etc as per F1 and McLaren at one time planning the car to fail 50 yards over the finish line. Good luck you seem to be as usual doing all the right stuff. Be careful with stop/start locations which can be stress raisers and the old adage if it looks neat and tidy its probably ok. Is it TIG you are using, I'm guessing so.

 

Enjoy

 

Bob

Thanks Bob, I'll take a look into the theories behind stop and start locations too in that case, I guessed they would form stress raisers but it'd be good to know the exact ins and outs.

I'll be using MIG actually, I don't have the kit (or skills!) for TIG, plus the people I bought the MIG from actually had some interesting relevant information. They did consultancy work for TVR when they were developing the Speed 12, and found that MIG actually gave stronger joints overall for chassis and roll cage welding - this was down to it being easier to get consistency with the MIG, mainly due to the awkward angles and tight locations found in a chassis, that can make it difficult for a 'less than highly skilled operator' with a TIG set.

 

Cheers!

Adam