casting a lug for a motorcycle frame 1

[motorq]

is it best to cast a lug for a motorcycle frame or forge it, I am in south africa and would like to repair a motorcycle frame that has been manufactured 40 years ago, any suggestions on how to approach the remanufacturing of the lug/s and what material/s to use, I have been unable to get a replacement frame, I am part of the local VMMC

 

[ornerynorsk]

If you are looking for a single piece-part, I would suggest having it machined out of a good quality steel, 4140 or similar. Might I ask, what is the make and model of the motorcycle that you are looking for parts?

 

[motorq]

Hi
It is a TR5 Trophy, the lug was cut and altered to change the neck angle in the 60's for a chopper, I have most of the original parts and would like to convert it back to original, thanks for the support
I would still like more info on casting the lug (and the material to use), this way it would be more original

 

[rhodie]

I am not an expert on casting, but I would think that casting the lug might introduce the occurances of inclusions and fissures into the piece- a piece that seems especially valuable in keeping you alive. Forging is probably the better than casting, but ornerynorsk's idea of getting one machined is best.

 

[motorq]

Forging sounds like the right route to go
Where can I find out more on forging and the tooling required, the material to use in this application is also important
I have acces to machining facilities and if I knew how to design the tool/s to forge a item, the shrinkage of the material and tolerances required and what material to ultimately use for the forging. I think I could cut the cost of a low production forging run
IE I would supply the tool and the material and the foundry would have to do the job
The machining is not an option because the motorcycle would then be of no value

 

[metman]

ornerynorsk's suggestion of 4140 is probably a good all around choice which will give you good strength and toughness if properly heat treated. I suggest final tempered hardness of 38-42HRC.

H11 or H13 Hot Work Tool Steel should work for forging.
Whoever you plan to do the forging for you can give you shrinkage info for macAhning the forging tools.

After machining the tools they will need to be heat treated by a competent heat treater. Tool steels require more particular understanding to correctly heat treat than most steel alloys.

Suggest after forging, you anneal the forging. The forging supplier should be able to provide this service for you. Next machine the 4140 then have it quenched and tempered to 38-42HRC.

Jesus is THE life,
Leonard

 

[GRoberts]

I think getting a casting would actually be the way to go. Since the motorcycle is over 40 years old, I would assume that the steering head was made from steel and not aluminum? Cast steel is used for critical applications every day, and a wood or foam pattern used for sand casting would be much cheaper than metal tooling for forging the low numbers you are talking about. If you are concerned about soundess, you can specify the foundy examine the casting with magnetic particle, x-ray or ultrasonic testing, which good foundries have in house. You can specify any acceptance criteria you feel is applicable and guarantee youself to get what you want.

 

[arunmrao]

Roberts I can see a casting man talking. Good that is the ideal way to manufacture and introduce adequate ndt inspection for assurance.

 

[GRoberts]

I do work for a founry right now, and China is driving foundries out of this counry (USA) for 2 reasons. First, they sell if for cheaper than it can be made here. Second, their castings are low quality, so when someone wants to use a Chinese casting for somehting that needs a quality casting, and it breaks. Then they think all castings are not fit for important applications, and that drives away business for foundries that do make quality castings.

 

[NickE]

As a metallurgist from MTU with my MS project in ironcasting I have to give you a star groberts, I'm tired of the layman having been convinced that casting makes weak parts.....




Nick
I love materials science!

 

[arunmrao]

I have to always approach a designer or a sourcing engineer sheepishly to convert a product into casting form. Just yesterday I had been to a manufacturer of rice milling equipments. A screw in high carbon steel 0.95%C and 1.25%Cr,0.5%Mo was machined out of a bar stock. This weihs about 20 kilos and is 900 mm long. They are apprehensive about the integrity of the casting. It took me a while to convince them and I had to do the extra sales in offering some discounts. This mindset seems to be universal.

As regards China I have no comments except it is killing us too in India.I know of a company in road building equipments who used ductile iron castings made in China and the machines failed in use. They have since been pulled out of service.

 

[etch]

Right gents im sick and tired at people saying casting are full of inclusions and defects, We currently make castings that are used in aerospace out of a357. the level of defect allowed under x-ray is nothing greater than level 1. In addition we also make Aluminium swingarms for both trail bikes and road bikes. These are one piece cast products that have bettered thier rival forged component in terms of cyclic fatigue. In additon we are producing a singel side swing arm which is also cast.

My moral is we are still beig driven by two things, Installed fear by forging comapnies who think they will lose out in business and the old school who still see castings as something done in a dirty old place and being a dark art. The casting technology has come a long way and most foundries now have degassing units, spectros, gas analysers, metal cleanliness, x-ray both real time and film. Cad/cam, and solidifcation software.

There was a good article written by boeing CEO that stated he wanted all his people to look at the savings that casting could make over forgings. One example is the wing rib in the new airbus, it used to be forged out of 7 parts and then had the problem of fitting alignment and such. this is now cast. In addition the new audi doo of the A2 is cast as one piece, albeit by thixoforming.

 

[arunmrao]

I shall wait for others to offer their opinion. Partly I blame the foundrymen for giving an image of Voodoism or black magic rather than a process based on scientific principles. Yes due toseveral complexities and the number of variables involved duringprocessing, it was not possible to provide a mathematical solution. To day with development of instrumentation most of the aspects can be measured and defined.

But now it is not possible to get young engineers or technicians attracted and the art or skill in manufacturing is dying,

 

[NickE]

I take mild offense to the not possible to get young engineers to be attracted to the casting industry...

I was a foundry guy, published in AFS, presented at conference, and got a masters of science from one of the top metallurgy schools in the world. After finishing school I moved to the big city, sent 400 targeted resumes, at least 1/4 of them were in the casting industry. After 1year I had one interview in a foundry, adn even then they were really looking for a manufacturing engineer. I really liked the thermo and stuff of castings, there were no jobs for me thou. Well now I have a great job w/ a good company, and even get to do a little bit of research now.




Nick
I love materials science!

 

[arunmrao]

Nick This will be my last posting in this thread. I wish to inform you that I have gone through your experience 20 years ago after completing a PhD program in ductile solidification and metallurgy. No industry or research institution offered me a job for over a year in India or overseas. I had publications in AFS, CMRJ, IBF etc. I had to take up a job as a Metallurgist later on. After 10 years I set up my small foundry business, Now after 10 years business is still shaky but I am enjoying my job as a foundryman producing castings.

 

[motorq]

Thanks for all the replies and I have learnt a lot, yet my problem is to manufacture a lug for a classic motorcycle that was manufactured 40 years ago to retain originality
I dont know whether it was a casting or a forging, has anyone got an idea or can anyone point me in the right direction for this kind of info
I can manufacture my own tooling and or patterns if I have the tolerances ie shrinkage etc
I assume it was a forging, yet I am not sure
If it is a forging I need info on tool design
Can anyone help me

 

[keithw]

It was wonderful to see so many of you take this opportunity to chalk up a hit on both sides of the casting/forging issue, but as MotorQ summarized in the end, you weren't really answering his question albeit it was not precisely stated in the first place. I believe that Groberts answered the best when it came to "matching" the original in that it would have been a casting.
For my own two-bits on the metal forming process, I have dealt with millions of cast and forged components from every part of this world and have seen porosity in castings from every country, but never in forgings. I still use both.
Have a great day.

 

[GRoberts]

I am not sure about older motorcycles, but on newer ones, the aluminum connections, such as the steering head, swing arm pivot, engine cases, are mostly castings or stampings. Without an original part, there is no way to tell unless someone just happens to know. If you have an original part, you could cross section it and observe if the microstructure is cast or if the material has been worked (forged).

 

[NickE]

I know that bicycle lugs are/were cast in the era you speak of. The frame tubes are then fit by hand and brazed into the lugs.



Nick
I love materials science!

 

[motorq]

The bicycle lugs are casts and look great no pockets or inclusions, I havent found a company locally that is able to do it to these standerds
The one I approached that was supposed to be technologically advanced, using CAM and lost wax process with ceramic moulds - had inclusions visable, that were the size of a rice grain
And this worried me
Last but not least, if anyone who has the knowledge could look at the neck lug of a 1949 to 1954 Pre Unit Triumph and tell me if it is a casting or a forging
The technology debate is very interesting and I am learning a lot
But I would like to remanufacture the lug to original, if possible
Thanks everyone for helping
On a more positive side, many people have approaced me subsequently for more info on this type of frame building and/or repair
And yes the closest thing to this is bicycle frame building