How hard can it be?!

[JanBros]

Silly question.
I lack the skills/software/equipment to do a proper strength/stress analysis. Should I spend a month learning the proper CAD software to do that kind of analysis or just go with a feels-good-looks-good-is-good way of working?

since I probably will never be able to drive your bike, I'd say go for the "feels-looks" solution.

however, if you ever decide to bring it over to Belgium and offer me a ride, I hope you took the learning-month

[RatsMC]

Silly question.
I lack the skills/software/equipment to do a proper strength/stress analysis. Should I spend a month learning the proper CAD software to do that kind of analysis or just go with a feels-good-looks-good-is-good way of working?

This, to me is a bit like learning to read music: it is tedious, boring, expensive and takes a long time. Acquiring and then learning the software will be the same but in the end, it is how to do it right. Many brilliant musicians can't read music and many brilliant builders can't use Solidworks but many less-than-brilliant musicians and builders keep up with their brilliant counterparts by learning the tools.

IMO, it depends on how much building you plan to do.

[heng47]

http://thekneeslider.com/archives/2008/ ... nd-update/

Looks interesting, but might be too heavy looking for my liking.

[heng47]

Just spent the past 2 nights trying to absorb everything in these 2 threads, lucky find.

http://www.vfrdiscussion.com/forum/inde ... kenviffer/
http://www.vfrdiscussion.com/forum/inde ... ffer-mkii/

[heng47]

This, to me is a bit like learning to read music: it is tedious, boring, expensive and takes a long time. Acquiring and then learning the software will be the same but in the end, it is how to do it right. Many brilliant musicians can't read music and many brilliant builders can't use Solidworks but many less-than-brilliant musicians and builders keep up with their brilliant counterparts by learning the tools.

IMO, it depends on how much building you plan to do.

I agree. Learning the software is not much of a problem to me because stuff like this seems to come naturally to me. Doesn't usually take me more than a couple of weeks to get good at any kind of software and I already have experience with 3 brands of surface modellers. I just haven't had the chance to use any solid modellers, I don't have the budget for them and the school only has stuff for the archi students. What I really want with CAD is quick visualisation and more importantly, a base to automatically calculate and generate length and angles instead of 'estimate-cut-repeat'.

Luckily, the last 2 frames made with this method didn't break (despite the lack of triangulation, and yes the rear shock is mounted in a VERY bad position).



For the time being, I'll stick with google sketchup.

[Oscar]

Heng: What a great way to learn a huge amount about mechanical design - but man, if you are going to ride the thing seriously, you are going to have to do some really intense basic research on structures.

Can I recommend a visit to the Tony Foale site: http://www.tonyfoale.com/ - the guy has been building specials since early Noah.

Some other cautions, not meant as a put-down in any way but stuff I have picked up from my family connections to aeronautical engineering and stuff I've done myself in constructing a few racing cars ( small sports cars called Clubman Class, like Lotus Super-7s but purely for racing).

Most aluminium alloys are very much affected by heat-treating and welding aluminium alloys can have serious effects on strength/brittleness. Research the effects of welding for your chosen alloy/s if that is part of your design.

4130 steel (generically, Chrome-Moly) is very susceptible to inter-granular degradation at welds and may require post-welding heat treatment. If using tig welding, use ER70 filler rod. ANY welded joint will 'pull' somewhat as the metal cools and if unable to do so, you can have a partially fractured joint straight off the torch. The order of welding tubes in a space-frame type structure can be very important - talk to an aircraft welder who does engine mounts if you go this route if you can't find a bike-frame specialist.

High-strength critical bolted structures may require 'interference-fit' bolts to obtain rated strength and accurate torque figures to ensure that the parts so bolted are under sufficient pressure that friction is obtained. Do you know that aircraft propellors (in most cases) actually rely on the friction of the hub/flange faces, not the actual bolts? The bolts are there to provide the clamping pressure for the friction to work!

Hope this is a bit useful and the project is a major source of satisfaction.

[heng47]

4130 steel (generically, Chrome-Moly) is very susceptible to inter-granular degradation at welds and may require post-welding heat treatment. If using tig welding, use ER70 filler rod. ANY welded joint will 'pull' somewhat as the metal cools and if unable to do so, you can have a partially fractured joint straight off the torch. The order of welding tubes in a space-frame type structure can be very important - talk to an aircraft welder who does engine mounts if you go this route if you can't find a bike-frame specialist.

Lots of great information, thanks!
I don't think there're any plane or bike builders in my area. There's a custom shop up several hours away in Kyoto so I'll swingby to ask some questions, but I don't think they make any custom frames. Before that ,could you shed more light on it?
I tried googling it but nothing relevant came up. I've been reading some of the frame-up builds in a few custom forums and it's been quite enlightening but no one mentioned anything about order of welds, there was something about watching being careful of the bending and warping during welding but it was controllable can be manipulated. The few discussions on the post weld tempering concluded that it was neither necessary nor cost effective on bike frames.

[heng47]

http://en.wikipedia.org/wiki/Interferen ... ance.22.29

Formulas exist to compute the "allowance" (planned difference from nominal size) that will result in various strengths of fit such as loose fit, light interference fit, and interference fit. The value of the allowance depends on which material is being used, how big the parts are, and what degree of tightness is desired. Such values have already been worked out in the past for many standard applications, and they are available to engineers in the form of tables, obviating the need for re-derivation. Thus if a loose fit is desired for a 10 mm (0.394 in) shaft made of 303 stainless steel, the engineer can look up the needed allowance in a reference book or computer program, rather than using a formula to calculate it.

Looks like this is going out of my hands.
As tight as can be with a touch of loctitie?

[TwoStroke Institute]

Just get John Bradley's books ASAP.

If you want to join tubes of 4130 together without post weld heat treatment you need to learn bronze welding(which again is covered extensively inthe above book), the find old push bikes(not hard in Japan) cut the tubes,practice welding them then perform a few destructive tests. YOu should be able to get the tube to deform and fail with the joint remaining intact.
You also need some background info on materials(the book again), you DO NOT want to use stainless steel in any sort of repeated stress/strain area, as it is brittle and work hardens very quickly.
Rats music analogy is a good one, Solidworks is an awesome tool(MasterCam/Pro E are arguably better) if you get a black belt in that the world is your oyster.It has Cosmos express for a basic Finite Element Analysis(FEA).As a while ago I read a story of 2 people arguing(1 engineer 1 machinist) if it took smart people could see what the layman could not. They devied an experiment where they joined 2 lengths of metal bar, went around the factory and asked everyone(from managers to the tea lady) to set the bars to a 'right angle' by eye. The result was nearly everyone was within 1 degree either way of 90deg, the biggest margin was 5 deg.
The old saying is 'If it doesn't look right it probably isn't"

If your interested in a Hossack front end I know a fellow that has the plans and is having a garage sale ATM.

[heng47]

I ordered vol 2 off Amazon JPN last week but it looks like they still had to get it from the US, should be here this Sunday.

I was planning to spend the remainder of May getting as much welding practise as possible as well as putting ideas down on paper first. I just googled it but by push bikes you meant bicycles, right?
I also googled destructive testing and will be trying this method. (originally, I thought of just throwing it against a concrete wall or off the roof of my faculty )

I don't think I need the actual front end but plans would be nice. How much?


After thinking hard about what Rats said regarding what I wanted from this build, I don't think I can actually produce a race-able frame and that isn't really the aim but I want it to be road-worthy (as in not break after the first pot hole) because I'd like to ride it down (as opposed to showing photos) to Moriwaki during the job interview. It won't actually be legal because I can't get a title but I don't think traffic cops exist in Motorsport City Suzuka.

In short, I want to build a bike that can get me into the industry to continue making more bikes, and so goes the circle of life.

[RatsMC]

Something to keep in mind: don't let yourself worry. There are countless rabbit holes you can head down as some of the technical challenges can seem insurmountable without decades of engineering experience but keep in mind that a bike isn't actually that complicated and guys with no training have been building them in garages for decades.

[TwoStroke Institute]

Yes that is the method I used(very simlar) sorry for the Aussie slang of a bicycle
If you want to impress a racing team, be sure you decide to be an engineer or a fabricator, as they may have separate departments. Idealy you want people who understand both sides.You want to be able to speak fluently about what aspects of frame design alter the characteritics of the bike.Understanding the economics of the industry would also help.
In racing, there is nothing radical, just evolution, so avant garde designs won't impress to much. Taking a basic design and improving that and explaining how, why,where and by how much it has improved will impress.
As Kel Curruthers once said "What wins this year will be what won last year plus a few percent"

[Oscar]

I tried googling it but nothing relevant came up. I've been reading some of the frame-up builds in a few custom forums and it's been quite enlightening but no one mentioned anything about order of welds, there was something about watching being careful of the bending and warping during welding but it was controllable can be manipulated. The few discussions on the post weld tempering concluded that it was neither necessary nor cost effective on bike frames.

Heng - I found a good article that says it better than I can express, and has a lot of useful info re jigs and welded motorcycle frames in general: http://www.knucklebusterinc.com/tech/FrameJigInfo.pdf

Here's an extract relevant to welding sequence:

It is imperative that the tubes are properly cut to length, bent and mitered so that the joints are as close to perfect as
possible. If this is done they can be positioned and held very lightly in place while they are tacked and if the welding
sequence is done correctly no heat distortion will change the angular or dimensional alignment of the various tube
members. The jig and fixtures no matter how strong or rigid cannot resist the bending and warping stresses caused by
improper welding sequence or inaccurate initial layout and fitting once the frame is removed from the jig.

One way to test your building skills is to fabricate a frame and then saw through some tubes near connection points at various places on the frame. If the tube end suddenly springs away from the other end or springs to one side or another at
the point of the cut it indicates that your frame has a lot of built up stress caused by poor welding sequence, too much
welding heat or poor structural design considerations. If you cut an unstressed tube the hack saw will pass through the
member and nothing happens, both ends stay in perfect alignment separated by about a sixteenth of an inch of air space.

Post-weld heat treating is the usual method used to release built-up stresses in highly-stressed tubular structures such as engine mounts, which typically are operating at the upper end of the material specification. I completely concur with TSI's comments that nickel-bronze brazing is a very good way of building a cro-mo frame PROVIDED that you are not operating at a stress level above that of the nickel-bronze itself - because it's basically a sort of metal 'glue' rather than a method of making two pieces of metal have a continuous granular structure AND you use only the absolute minimum of heat required to get the nickel-bronze to run properly - otherwise you can get intergranular degradation of the steel and the joint will tear apart actually in the steel at the edge of the brazed area - it will fail before the nickel-bronze does.

We used to use nickel-bronze brazing for suspension and chassis components and had very, very few problems, but you do need to try to design your welds so they have adequate weld area - a 90-degree butt join between tubes was the worst possible design and usually needed fillet plates to obtain adequate strength. TSI's comments re practising on old cro-mo bike frames is absolutely spot-on, you'll be amazed at how much strength a nickel-bronze braze will have when done properly.

Assessing the correct sequence for the tubes is something for which experience is invaluable but -VERY roughly - if you build any triangulated structure and then try to add tubes on the axes of already closed triangles, the latter tubes can't pull together so the last end welded can't shrink - the weld/inter-weld zone will usually crack as it cools and shrinks. So what you have to do is sequence the welds so the last one is the one that 'closes' the triangle.

Also completely concur with TSI that pretty much all of the 'commercial' stainless is really not good stuff for a stiff structure - I believe there are some (very difficult to obtain) stainless alloys that won't work harden very much but they're really hard to get hold of and often you have to buy a minimum quantity.

[Pantah]

I



After thinking hard about what Rats said regarding what I wanted from this build, I don't think I can actually produce a race-able frame and that isn't really the aim but I want it to be road-worthy (as in not break after the first pot hole) because I'd like to ride it down (as opposed to showing photos) to Moriwaki during the job interview. It won't actually be legal because I can't get a title but I don't think traffic cops exist in Motorsport City Suzuka.

Hire yourself a K truck for a couple of days and transport your creation to Suzuka,Heng........Dont ride an unregisterable bike down there,cause if Moriwaki knows that,then you wont get the job.........
The project sounds fun.Im looking forward to seeing some pics. All the best. By the way,speaking of Suzuka,are you going to the 8 hour this year?

[heng47]

Assessing the correct sequence for the tubes is something for which experience is invaluable but -VERY roughly - if you build any triangulated structure and then try to add tubes on the axes of already closed triangles, the latter tubes can't pull together so the last end welded can't shrink - the weld/inter-weld zone will usually crack as it cools and shrinks. So what you have to do is sequence the welds so the last one is the one that 'closes' the triangle.

Also completely concur with TSI that pretty much all of the 'commercial' stainless is really not good stuff for a stiff structure - I believe there are some (very difficult to obtain) stainless alloys that won't work harden very much but they're really hard to get hold of and often you have to buy a minimum quantity.

Incredible! Thank you!
I'll speak with the school's lab instructor and see what he knows. The previous guy basically knew everything in the universe and held our hand through building those solar car frames but he hurt his spine and had to retire. The new guy, while cool, isn't as experienced. Now there's no one in the school that knows how to operate the CNC machine so we're left with working on the 2axis mill.

I guess you guys are right re: the material. I just though stainless steel was a better option than mild steel. Just found a place that stocks chromoly and will get that instead. Is stainless be fine for header pipes? I've read that aluminum can be used from the collector onwards but it will go soft if placed at the header because of the heat.

[RatsMC]

I have always used stainless for the full exhaust but my exhausts have typically been pretty short. I am not sure I have ever seen aluminum used on pipes for bikes. Someone who actually knows stuff might have a better perspective on whether it is possible or not.

[heng47]

Hire yourself a K truck for a couple of days and transport your creation to Suzuka,Heng........Dont ride an unregisterable bike down there,cause if Moriwaki knows that,then you wont get the job.........
The project sounds fun.Im looking forward to seeing some pics. All the best. By the way,speaking of Suzuka,are you going to the 8 hour this year?

I actually have a title but since it's a custom frame I don't think it's considered titled anymore...
You might be right, I wasn't sure who to consult over this. Most of the locals would probably say no-no rules are rules but some of the smaller shops around here really like the idea of a fully custom frame and you know, as long as you have a valid shaken anything goes. There's a Harley shop nearby so I see some crazy ape-hangers once in a while. And then there's also the apes and monkeys with custom frames. I went for an interview at a company designing frames, they even had a self-designed prototype engine in one of their frames, they slapped on a title from a monkey and it was "don't ask don't tell " with the cops. You could tell with a glance that it wasn't factory because the whole engine was milled. I was more impressed that it was a working aluminum engine, I wonder why it doesn't melt.

I should be attending the 8 hours, as long as classes don't clash with it, I have a presentation on the 19th and typically have meetings on Fridays, will go Sat morning if that's the case. Will be bringing my gf along so I don't think we'll camp. I'd really like to get a paddock pass to have a nice close look at the bikes but she isn't interested in that kind of stuff..... we're just 'passing by' on the way to Nagoya

[Pantah]

Hire yourself a K truck for a couple of days and transport your creation to Suzuka,Heng........Dont ride an unregisterable bike down there,cause if Moriwaki knows that,then you wont get the job.........
The project sounds fun.Im looking forward to seeing some pics. All the best. By the way,speaking of Suzuka,are you going to the 8 hour this year?

I actually have a title but since it's a custom frame I don't think it's considered titled anymore...
You might be right, I wasn't sure who to consult over this. Most of the locals would probably say no-no rules are rules but some of the smaller shops around here really like the idea of a fully custom frame and you know, as long as you have a valid shaken anything goes. There's a Harley shop nearby so I see some crazy ape-hangers once in a while. And then there's also the apes and monkeys with custom frames. I went for an interview at a company designing frames, they even had a self-designed prototype engine in one of their frames, they slapped on a title from a monkey and it was "don't ask don't tell " with the cops. You could tell with a glance that it wasn't factory because the whole engine was milled. I was more impressed that it was a working aluminum engine, I wonder why it doesn't melt.

I should be attending the 8 hours, as long as classes don't clash with it, I have a presentation on the 19th and typically have meetings on Fridays, will go Sat morning if that's the case. Will be bringing my gf along so I don't think we'll camp. I'd really like to get a paddock pass to have a nice close look at the bikes but she isn't interested in that kind of stuff..... we're just 'passing by' on the way to Nagoya

Oh,well,in that case you may be ok to ride.If its still a VTR and has a number and the rego is paid up....good luck with it.
Im not sure if I will be at Suzuka yet,as we have a baby due that weekend. Could get a little complicated...........

[heng47]

There's nothing like celebrating the birth of a new life with the sound of horse power
Congrats!

[TwoStroke Institute]

Oscar I have used manganese bronze it's a bit more ductile than the nickel which is what cars and karts are welded with. The nickel is very tough though. I always reccomend bronze for beginners, as once 'tinning' has been mastered the two tubes won't pull apart, I like to then put about a 1/4in or 6mm fillet of bronze in there giving the join a nice curve. If I tig one I try to do something similar. The use of 'Temp sticks' is advisable to ensure no over heating of the tubes. That and big gaps between the tubes are the main cause of joint failures.
Heng Aluminium is only used for the end can, and that is pretty rare these days. Exhausts are Stainless for OEM stuff then you move to titanium for aftermarket stuff and I have yet to see a Innconel motorcycle exhaust but I suppose it's coming.

[Oscar]

Oscar I have used manganese bronze it's a bit more ductile than the nickel which is what cars and karts are welded with. The nickel is very tough though. I always reccomend bronze for beginners, as once 'tinning' has been mastered the two tubes won't pull apart, I like to then put about a 1/4in or 6mm fillet of bronze in there giving the join a nice curve. If I tig one I try to do something similar. The use of 'Temp sticks' is advisable to ensure no over heating of the tubes.

TSI - yep, the manganese certainly has a bit more give, but for rod-end fittings in suspension and suchlike I prefer the strong stuff. I found that by using a soft flame - turn the regulators down a bit - and my Zeiss Umbral sunglasses with the brown tint rather than normal gas goggles I could really see the weld pool running and not over-heat the tubes. You could see the tube coming up to deep cherry and the flux running and just dab in the bronze gently. A decent fillet is always the go, for sure, and easy to get with the softer flame - when I started I used to blow the bronze away with too much gas pressure, went up a size in tip and wound the regulators back a little and hey presto, it all became so easy! With Tig, I usually spot the tube join at a few places before running the fillet so the buggers can't pull out of line from too fast cooling of the welded side of the join - I love Tig but it does have its little tricks, as you'd know very well - that's a comment Heng might find useful, however.

Jig design is an art in itself - my brother is an aeronautical engineer (and held an aircraft gas welding ticket for a while), and for his own aircraft that he's building with a tube-frame cockpit (and for his engine mounts) he designed jigs that turn on a spit, as it were, so most of the welding is downhand, and gee it makes life easier! It took one iteration of the cockpit in mild tube to work out the best placing for jig attachments so they are all NOT where you need to weld before he started cutting the 4130 - time consuming but the jigs are ultimately intended for small-scale production.

[heng47]

The book arrived last night, reading it.
Spoke with our lab technician and he doesn't know how to do chromoly, says he can guide with the steel and aluminum parts but I'm on my own for chromoly. This is getting more and more fun every day.

[TwoStroke Institute]

True, and sadly with jigs they start to become the project, rather than the means to make the item. As factors like the life of the jig, space constraints and the cost of the bloody thing !
Then after the items have been made you have to think where your going to store it, cut it up for scrap or some other worthwhile practice. As by that stage I have seen enough of it.
On a side note can you ask your bro thinks and what CASA standards are for tig welding 2 tubes of 4130 together? I get people try to tell me that 316 stainless is the best because it has similar materials(I just think they say that because 316 'flows' well and the weld looks pretty). John Bradley's book reccomends against that and says first use bronze and if they are to be electric arc welded then with 4130 CrMo filler followed by post weld heat treatment. I wonder what CASA states as heat treating a airframe would be difficult and expensive.
Ooops sorry I haven't replied to your email

Heng, just put it under your pillow and when you sleep the info sinks in That will be the best money you ever spend

[heng47]

Heng, just put it under your pillow and when you sleep the info sinks in That will be the best money you ever spend

There might be some truth in that, I actually read a science report on the BBC that mentions taking a nap after doing some studying helps people to remember stuff.

[heng47]

What would be a good way to get dimensions for the engine mounting points?

One idea I have in mind is to remove the engine from the frame, prop it up with blocks of wood to where it would be if in a frame, then mount 2 planks of wood on both sides and just eyeball it from there.


Another problem I'm having is with defining the wheel base and overall dimensions. Would it be more recommendable to try to keep close to the original VTR's dimenions?
I don't think there's really anyway for me to determine an optimum wheelbase or steering angle without proper road-testing so I'm thinking of using the differences between the CB and CBR as a reference and just play around with it from there. Most importantly, it should fit me since I happen to almost be of average (asian) size.

I could get it on scales later in the build to rough out the weight balance.. Norman Hossack did recommend a 50/50 ratio as better for his fronts.