High tensile bar/rod?

[inchpincher]

I need to fabricate a main engine bolt for a custom scooter frame, the previous one had started to bend under load. Rough dimensions are maybe 16mmx400mm but it obviously will need a thread cut in each end to attach via nuts.

A couple of questions, what 'type' of steel should i be asking around for (does high carbon mean high tensile?) and are there different requirements for welding high tensile steel compared to mild?

thanks,

 

[breezer]

Off topic Ben but do P13 do paintwork?

 

[breezer]

What do you need to weld to it btw?

 

[inchpincher]

Hi jim,

we're trying out a new paint guy but it's real pricey. Hopefully we can start doing the panel beating and filler prep in house so i'm guessing the costs will at least half... Trevor designs and overlays all the graphics then the body's get lacquered. I need to take some pics and put on the smallie forum cause they're very unique.

Not sure if you ever saw this mad project i bought a while back, custom fatspeed frame with a gilera vtr 180 4-t motor, aprilia sr forks, 14 inch wheels front & back, ducati shock, lammy legshields horncast and loop etc. Re the welding, i was just gonna attach one of the nuts to the end of the (hopefully high tensile) engine bolt to stop it all spinning around a la lambretta engine bolts... And im curious to know if ya can weld it without removing the hardened properties

 

[breezer]

Fair play - hadn't seen that before. That Fattspeed's a talented fella.

I'll stop thread-jacking now anyway

 

[inchpincher]

I'll pm a bunch of links to how the frame's changed over the last couple of owners lol...

Back on subject - anyone recommend the correct type of steel for my application please??

http://www.westyorkssteel.com/carbon_and_alloy_steel.html

 

[scott0031]

En8 will be fine for what you need, its a common grade available in many sizes used for such applications. As you say you are better off threading both ends and use nylocks, it will save having one machined or having heads welding on, although this is perfectly safe if done correctly.


It can be welded successfully most use standard wires but it does really depend on the application. If it only needs to be retained by nuts/head then standard filler will probably do the job. if it needs to be loaded up then its best to wait for someone like technical al or hotrodder to give a wire grade as they will be better qualified than myself to comment.



Kind regards,


Scott (ward engineering)

 

[hotrodder]

There's been a bunch of articles added to the 'DIY guide' section of the site. Al's done one for, amongst others engineering steels

Any chance of some pics of the problem so those of us that can't picture it can get an idea of how it's loaded/become bent? I'm probably picturing it wrong but am thinking an undermatched weld will be fine as it's the length of the thing that's the issue.

 

[gridley51]

EN8 is ok but the best stuff is EN24T. Hard bit will be finding someone prepared to sell a small piece.

 

[inchpincher]

Thank you fellas, a good starting point to research.

Hotrodder - the frame is in my dads shed at the moment so until i dig it out next week i've only got pictures i'd taken last year or inherited from previous owners forum threads so here goes...

Basically the frame mount was made too wide for the donor engine, here's how it looked at first conception...

Once the fabricator had modified the engine mount point...

The next owner then changed the 'loop' section for a different fibre glass rear end...

This has never been on the road, the bar they were using as a temporary engine bolt had started to bend before they modified the frame mount but i still want something high strength down there...?

 

[Uniqueusername]

You shouldn't need anything tougher than boggo mild steel for that, if you do there's something bad with the joint design.
(Ex bike modifier, winch mount builder and a lot of other very high demand things)
If you can't replace that bolt with a length of soft bar and some split pins then something's amiss..........

 

[breezer]

split pins...

(goggle eyed smiley!)

 

[Pete.]

Engine mount bolts should never bend because they are designed to work in tension, by clamping the engine to the frame, and in shear. If you are bending the bolt you must be putting some lateral forces through it, which shouldn't ever happen. You need to re-think your design.