Full Suspension Frame - new linkage

I have now made a carbon (with alloy inserts) linkage, I had taken about 20 photos of making it but they seem to have got corrupted somehow, so I guess a few photos of the finished article will have to do.

The change in linkage design has changed the travel slightly, but not by much (from 94mm to 96mm), it has also changed the leverage ratios to a falling rate, this is not what I was hoping for, but a quick spin suggests there is a little less pedal bob, so I'm going to test it as is for a while, as I would need to move the linkage pivot location to change to a rising rate.

I'll try to get out of a quick spin either this evening or tomorrow to test it out properly, but from a quick spin down the road and back it seems to work well!

Full Suspension Frame - first rides report

Ride 1

The cables and hoses arrived over the weekend so after fitting them I managed my first proper ride on the new frame today. 

I started of extremely cautious, but after a few minutes I had almost forgotten and started pushing quite hard and not slowing for bumps. Part of the route had a section of  dried plowed field and I was able to carry quite a bit more speed  compared to the hardtail, without any cracking or damage to the frame, both while standing and sat down. On long smooth climbs I found there was a little bobbing, but not too bad and putting the shock in pro-pedal mode stopped it completely. 

As would be expected from a full sus, on steep climbs traction was improved compared to the hardtail. I also didn't have any unexpected flex from any parts of the frame so I'm looking forward to testing it over the next few days!

Ride 2

On the second ride I noticed I rather alarming knocking sounds when pedaling hard - I tried to work out what it was and tighten all accessible bolts, but nothing seemed to do anything. When I got home I pulled the cranks out and tighten the main pivot and that seems to have sorted it - but can't see how it's making the noise so I'll be keeping an eye on it at afan!

Full Suspension Frame - Part 15 - It's done!!! (almost)

After nearly 3 weeks of building the frame is now functionally finished! I have taken it for a quick spin and it feels nice and stiff, with only a few minimal cracking sounds- I know from doing the hardtail to expect a few creaks/crack sounds for the first ride or so - but after that I hope it will be as silent as the hardtail is now.

I'm happy with the final look of the frame, although I need to do quite a bit of work on the finish quality on places. I'm still waiting on cables and hoses but from riding is ss with just the front brake I can tell it rides reasonably nicely, I set the pressure in the shock quite low and was able to bottom it out without any parts of the frame fouling on each other or the tyre.

The mod to shorten the chainstay/swingarm has also raised it by about 5-6mm, which also means that it is quite close to the chain, with a clutch mech and a chainstay protector it shouldn't be to much a problem, although on the V2 I will drop it by about 6mm..

The rear pivot and dropouts area need cleaning up and possibly painting, but nothing structural need to be done. 

The front mech looks pretty good, but I think direct mount mechs always look worse than band on types - but I would have had to compromise the strength of the frame to fit one.

Full Suspension Frame - Part 14 - final weights and a small clearance issue

With all the parts a nearly done, I decided to weigh them before assembly, to see how close to target weight I am. 

I weighed the front triangle with a BB in place so the actual weight is 1186g - which is 86g heavier than my target of 1100g so I'm reasonably happy with this. 

The swingarm ended up weighing in at 667g (pre discovering problem below) which is a 217g heavier than targeted, and will be the next area of development as I intend on remaking it in full carbon to hopefully get it down to about 450g.

The seatstay piece is 239g which is 61g lighter than I had targeted (300g). I'm happy with this, but it does leave room to beef it up if I feel it needs it after testing it.

I assembled the frame and it weighs in at 2580g (including shock and all hardware) this is heavier than targeted but for a first prototype I'm not too displeased and I know where I can reasonably easily shed 200g

I started to test components for fit and I came across a pretty major issue - the cranks didn't fit! - Where I had shortened the swingarm I had forgotten to recheck if the was enough room for chainrings, I have removed about 10mm of material off  the outside of the arm and built up the inner side so not to lose any strength, when I make the v2 swingarm I will make sure I remember to check for clearances before fitting it! 

Full Suspension Frame - Part 13 - derailleur mount and seatstay

 After leaving everything to set over a couple of days I was able to do another mockup of how the bike will be, I'm now a lot more happy with the chainstay (429mm) and was able to set the BB height with a block of foam.

A have also checked the amount of travel possible - and I think it would be able to get about 135 without touching the seattube

The wheel seems to be about 1-2mm of center - but this isn't to much of an issue- my hardtail is about 3mm off!

To fit a front derailleur I have had to make a aluminium plate for a direct mount front mech - using the dimensions from the drawing below

I'm setting the seatstay in situ so to make sure it is 100% aligned, but this means I'll have to do the rest of the finishing layup tomorrow.

Full Suspension Frame - Part 12 - measure twice, cut once.....

One update for two days work due to not getting much done (the F1 was on this weekend!) and having to go back a few steps due to a pretty major measurement mistake. 

 I put a set of wheels in the swingarm frame to test for fit as alignment and it was immediately apparent I had made an error due to having chainstays in the area of 465mm it was also obvious due to the gap between the rear wheel and the seattube.

After a bit of thinking I worked out what I had done to add 35mm to the chainstay length, firstly when making the parks of the swingarm I had used an old CAD drawing which used a pivot mount forward of the bb which accounted for about 30mm of the increase, secondly I had put the pivot 5mm further back than designed.

because of this I decided to cut and remove the metal inserts, which was a lot harder than I thought it would be, and then redesign it about 30mm shorter, I have also moved the pivot inboard by about 5mm, rebuilding that area for the 3rd time! 

 The new improved swingarm will use pretty much the same design, but with a smaller shelf between the tyre and the bb to cut some length out of it.

I also continued work on the seat stays, where I have now bonded the lower end onto them ready to be finished when the swingarm and main pivot are set completely and I can jig them up in the frame.

Project 2 in the pipelines - Full suspension XC 26er/650b frame

I like my hardtail as it is extremely fast, nimble and excellent for xco length races, but it can be a little harsh on longer rides. With aspirations of competing in longer events and one day riding the BC Bike Race (and other multi day stage races), I have decided to attempt to build a full suspension frame...

To begin with I have started researching the existing options available on the market and their respective suspension geometries - the two main bikes I looked at were the Scott Spark and Rocky Mountain Element, both of these are 29ers (apart from the spark with which they now make a 650b version too), but the basic kinematics and linkage design will be the same no matter the wheel size.

The Element RSL- the main inspiration for my bike 
I was advised to use the Linkage X3 software - and it turns out it's brilliant, it has allowed me to to design the exact pivot locations and how it affects the bikes handling. I have decided on a faux bar suspension linkage design (called 4 bar in Linkage X3 for some reason?), as it allows me to create a rigid swingarm and a lightweight arm to actuate the shock. I plan on 100mm travel, and using 26 inch wheels initially, but designing the frame with slightly variable geometry so I can put 650b later on.

The design of the geometry as of today.

I have got hold of a Pinnacle Arrow frame to use as a donor bike  - I'm yet to see it in person, but I hope to be able to use the dropouts and the bottom bracket shell. I will also look at the quality and shape of the carbon seatstay and see if it's worth using my frame. I may also use the headtube depending on whether it's moddable to a tapered design

A Pinnacle arrow - seems a shame to cut up such a nice bike - but it was cheap, and fits what I need!

I'll post the next update when I begin the making!

Full Suspension Frame - Part 2 - more designs by request

I have been asked if I could show some of the more detailed designs and the CAD that I have done for this and to explain the design process that I have used to get to them - so here goes.

 So to start with I made a rough model of the front triangle (blue part) in NX8.5, but I made sure all the pivot points, BB, headset and dropouts were located in the right places. I then started to build the individual components up around this. My plan for the CAD model was more to get an idea of the spaces I will have available to locate the pivots, rather than design them.

The main pivot will be the most crucial as the majority of the torsional forces will be transmitted through it, my plan is to overbuild the area slightly so to be sure it holds up.

Here is a rough sketch of how I intend to do the main pivot - I plan on using two bearings housed in a steel insert that will be bonded into the frame, I will then have a 12mm axle that the swingarm will be attached to, which should hopefully be rigid enough! The blue signifies where I will put a nylon washer on each side to allow for tolerances to be slightly off without creating play.  

These are the bearings I hope to use - the flange should allow me to locate the bearings exactly where I want them without any complicated retention methods.

For the top linkages I intend to use mainly nylon bushes mainly for the sake of simplicity and saving weight, but also they are significantly cheaper to get hold of (about 50p each). The drawing below shows one half of the shock/linkage/chainstay joint, the red writing signifies the rough widths of each part - so 34mm for each side with a total width of 68mm, which I feel is the upper limit before you will start catching your knees in the case of an accident. I will use a standard shock mount from with a 10mm center hole to allow me to run a single shaft through the whole assembly. 

For the more simple linkages I will just use a simple nylon bushing, that I will put a 10mm steel bar through so should rotate nicely, and be really simple and cheap to maintain.

Any questions feel free to message me or comment on here and I will try to answer!

Full Suspension Frame - Part 3 - Building begins

As I have a couple of days off after my January exams, I decided I would come home to get started on the build. I ordered a piece of blue modeling foam 200x500x600mm as it was cheaper than a piece 70mm thick, and would leave me with plenty spare. So after about 20 minutes of cutting with the longest saw in the garage I finally had a piece 70mm thick as required.

This is the 1:1 scale template I will use to make the jig and cut the foam is now complete. I have opted to use a straight top tube and a tapered down tube, it will remain 65mm wide throughout it's length, but it will taper from 70mm at the top down to 50mm at the bottom bracket.

The tape I will be using to compress the carbon will be this green 30mm wide electrical tape, I have 240m which should hopefully be enough. I am using green as I found the black tape I used on the hardtail was hard to remove completely as it blended in with the carbon fibre when set.

The bottom bracket shell off the donor bike cleaned up pretty nicely, and comes in at 57g, which compared to the 97g bb shell  I used on my hardtail project is quite impressive.

For the headtube I have decided bond headset cups into a carbon tube, rather than to use a donor headtube, I'm using a superstar tapered headset as it has quite large flanges on the upper cup, and 25mm flanges for the lower cup, so a decent bond will be possible, this method should be about 75g lighter and no less durable.

For the seattube I have used a slightly cracked Boardman seatpost wrapped with a thin layer of tape as a mold, this is is the same method as I used on the hardtail.  

Here are all the pieces previously described now wrapped in carbon fibre and the green electrical tape - I will try to update asap with how they have come out.  

Full Suspension Frame - Part 4 - The Jig, The core and putting it together!

Today's building went well, I have been able to build the jig, make the foam core for the front triangle and assemble the BB shell, seattube and headtube into the frame with the first layers of carbon, below are the 3 pieces i left to set last night, all came out well, and the seatpost wasn't too hard to remove from the seatpost.

Here are the same parts in the positions they will be on the frame with the paper template ans the foam I made the core out of.

 The production stages of the foam core...

The jig is made up of a sheet of MDF which I have supported the components on- I have made the center line of the frame 15cm out from the MDF so I can reach behind it when laminating the carbon fibre.

 here I have placed the foam core in place ready to add the first layer of carbon to hold it all together.

And voila! the carbon will be left overnight to set and I will add some photos in the next update with how it has turned out, hopefully with the next pieces of the build too!.