Tz 750 tank and seat

Tank and seat shaped and painted. Tank needs clear coating

Minimalist bench

Made from old rough internal bracing timbers. Sunken bracing, hand planed and stained dark oak.

Turned out really well.

Tz 750 engine

Making the base engine shape didn't take too long. I obsessed a bit over making a hollow box but in the end I made it from solid.  It weighs next to nothing really.

Annoyingly I had no wood large enough to make out of a single piece.  The cases and barrels are seperate, just like the real thing.....  2 disks make clutch/alternator covers.  This will be sanded and stained black, apart from the "head" which will be silver.

Basic bodywork

After wondering about making and attaching the tank I decided to knock the strengthening rib off the frame.  I am making the tank from a bit of plank I have lying around, I can therefore use the tank to add strength to the frame.  I made the sides from plank and the core I laminated from the same 4mm ply I used for the frame.  This makes it a snug fit ready for glueing once painted.

I also made the seat in the same way.

Here I made a late addition to the seat rear.  Originally it looked a bit too thin in comparison to the tank so I added an additional piece.  It gives it a bit more curvature.  I am also angling the whole piece up to the rear slightly (hence the gap in themiddle) to get the lines correct with the bottom of the tank.

Frontend on!

After lining everthing up I found that the headstock was too far forward.  It was fine but I want this to look compact, almost cartoonish and keep it small for the little lady.  With that in mind we redid the headstock, moving it back about 2.5 inches.  When I say "we" I refer to the odd time I work on this at my Dads.  When working with "The Fast Fossil" you tend to stand around while he starts a flurry of activity, producing a part before you have thought about what to do...

Here you can see the shorter frame and to be honest it looks much better.  It is also in a thicker section of wood so will be stronger as well, always a plus.  You can also see the attached swingarm with basic shaping to it.  I was going to have it with small radius on the front edge but I am now thinking of rounding it down to avoid little heels hitting it when scooting around.  I need to make the "twin shock" uprights for the swingarm as thats what the TZ flattracker had and it will not be strong enough as it is.

Here is the fork/triple clamp in place.  Currently it just has two bolds going into the headstock but I will be making a single bar going through the whole lot.

It is starting to take shape and looks like a bike.

I had to scallop the bottom triple clamp as it was hitting the downtube when the steering was moved left/right.  In retrospect I should have finished and painted the forks and clamps before gluing them up (only the top clamp is glued) but it wont be too difficult to finish them off.

The Frontend

The build has been lagging a bit of late, too many things to do!

Time to make the frontend though (yaay) and get it into a rolling chassis at the very least.  Looking at existing designs for wooden balance bikes they tend to use a sheet of ply, typically 24mm thick or so.  I think they look ok but for this i think it would spoil it a bit so am after something a little more realistic.

A trip to a hardware store and I found this.

£3.99 for the broom with a handle thick enough (from the looks of it).  I had to try a few of them though as they seemed to be randomly bendy or stiff.  This was the stiffest handle of the (identical) brooms.

I aim to use this as the fork legs.  I made up some "triple clamps" out of plywood.

They are the right shape but need finishing off etc.

The assembled frontend looks pretty neat even though they need a bit of tlc with the sander and some paint.

They feel stiff enough, I was a bit concerned about the bottoms but once bolted up they will be great!

Next up, how to attach them.  After a bit of deliberation we went with an alluminium tube with a plate welded down the center.  The plan is to channel out the frame and slot this in, glued and bolted to create a strong headstock that looks neat.

The metal headstock is shown here.  Tig welded, its strong and neat.

 The frame with a slot cut out to accept the plate section of the headstock.  To make it slightly neater still a hole was drilled and then the frame cut through the hole just forward of the hole center.  Doing this allowed a semi-sunken tube location rather than have it stuck on the end of a flat cut.

Here is the tube in place.  Even in its unfinished state it looks neat.  The surrounding wood will be sanded so it smoothly surrounds the tube.

Next up will be the engine, I have made the rough blank for the cases and barrel shape already.  

(Not so) Swinging Arm

I realized after cutting the frame blanks that I forgot to modify the templates to account for a change in how I am attaching the rear swingarm+uprights.  Originally I was going to have straight wooden beams acting as the swingarm but, as ever, when mocking it up in cardboard the spread at the rear was huge to account for it going from 2.5" to 4" (at the axle) in just 6" of length.  These were to be clamped onto the frame using bolts. I changed the design to make curved swingarm sides that are glued (and pinned) to the frame at an oversized mounting point.

When I cut the frame I forgot to add this oversized section, I had already transfered the template to the wood and with one thing or another made the "first cut" after coming back to it days after making changes to the design!  I was about to make another but decided to try and retrofit some disks onto it.  If it doesn't work I can always cut my losses and do it again.

 So I cut out enough disks to pad the mounting point to the required 2.5" and glued them onto the frame with a 6mm threaded bar through the whole lot with nuts+washers at the ends.  It looks like it will be more than strong enough which is good.  Once the swingarms are done I will drill the 6mm hole and clamp them to the frame with the bar+nuts before shaping it.  Once shaped I will be glueing it all up, clamping it on the rod and hiding the nuts (somehow).

So, onto the curved swingarm...  As previously mentioned bending the 4mm ply I have is a bit sketchy, it is prone to cracking with fairly minimal bending so I steamed it first.  Works well enough.  I made a jig out of some wood, made sure everything was square and glued+clamped.

 

In these pics you can see some leftover circles I used on the frame.  I will put pics of that up when I remember...

 Out of the jig the arms retained the curves with no perceptable springback which was good.

Next up I will be shaping these blanks and making the uprights that will serve as the twin shock setup the TZ750 FlatTracker used.

Main frame done (sort of)

Today I managed to get the main frame sanded and shaped.

I cleaned the raw laminate edges with a flapper disk + angle grinder and gave it the rough curves as a start.

So I sanded this down by hand using 80 grit paper and some small wood blocks I made.  I also used a thin piece of foam between the paper and wood block to get a smoother curve.  It looks quite trick in the flesh, the photos seem to pick up all the flaws...

I decided that the seat base, which was to be a bit of ply board sat on top of the rear frame section, should become a stiffening rib running from midway down the headstock upper to the rear section.

This involved making a curved piece of laminate.  Looking at 4mm ply you would think it would be quite flexible but the stuff I have is actually brittle.  I can get a bend that is fairly relaxed but anything remotely useful, even the radius of a rear tractor tyre will crack it.

I tried to ease it down onto the frame but it cracked (2 attempts).  I then steamed a piece over the kettle, hey presto it worked!!

So, steaming 2 pieces then screwing them in place for 10 mins created a decent fitting curved top plate.  I glued it all up and screwed it down hard.

NExt up I will be shaping the top piece then I might put some stain on.  Not sure yet...  I might not though as its not 100% finished, I need to finalise the headstock and make the swingarm/twinshock uprights and attach them.  At the mo I am thinking of using a hardwood dowel and glue to fix them in place.  I was hoping to bend them but after todays bending I am not sure the wood I have can get the bend I am after, at least not with my skillz.  We shall see.

Out of the mould

Well, not exactly a mould but the clamps are off!

I was concerned that it might not be as stiff as I wanted but the addition of the two outer layers really increased its strength.  IT takes considerable effort to bend it which, when combined with the lateral strengthening seat and tank base panels will be strong enough to support an adult (yaay).

In the pic you can see the mess my jigsaw makes of the outer plywood layer when cutting.  I tried a few things to stop it (including sandwiching it between layers ) but I guess my blade isn't ideal for thin ply (I got it for cutting conti boards a few years ago).  Still, I left enough overhang for it not to be a problem whtn I remove the excess and put the final finish on.

Hopefully at some point today I will start to finish off this piece ready for staining.  I was going to paint the frame black but having seen some examples of sanded plywood I think the natural patterns on it look really cool.  I got some ebony exterior wood stain so while it will look black at closer inspection you will get the wood grains.

Next up will be the swingarm and "twinshock" uprights then the forks.

Once the bike is a compelte rolling chassis I will start on the engine, tank, seat shape and exhausts.  I knocked up a quick drawing to see how it might look...

I can't wait! er to see my daughter on it!

Final Frame Lamination

With the 3 sheet core done it was time to lighten it then put on the final exterior sheets.

I was going to put pics of an expertly lightened core up but I forgot to borrow hole cutters from my dad (boo hiss) so used the largest drill bit I had (18mm).  This "hack job" would serve no purpose other than to be a lesson to me alone and as such there is no photographic evidence.

So without further ado I glued on my outer skins.  Having learnt from my previous clamping I used some spanners to spread the load.  This worked well as the clamps can put enough force on the damage the wood so spreading it out is no problem.

I stuck it in the spare room on some boards to catch any drips...

The end user taking an early look, she seemed to find it interesting.

So, when this is dry I will "shape" it which sounds fancy but really its just sanding, shaving etc.  I made the outer skins with a bit of overhang over the core as the jigsaw picked up the fibres slightly on the outer ply and also it gives me a little more practice material to remove!

Progress

I left the frames "core" laminate to dry overnight in the garage.  Unfortunately it was freezing overnight so it failed to go off.  I brought it in from the cold and put it on the dining room radiator.  I also noticed that one section wasn't glued up so I injected some between the sheets and reclamped that bit.

This was left for around 6 hours on the radiator.  When I came back it was all set (and toasty warm).  IT was stiff enough for a 12mm lamination but not quite as stiff as I hoped.  Still there is another 8mm of wood to go onto it.

So, just the lightning holes and final exterior sections to go on!

The first Cut

Time for the first cut!!!

AFter transfering the template onto one of my 4x4 sheets I cut a strip off (I get 2 frames per strip ).  After struggling with my "Jet" saw I got out my jigsaw which made short work of the paltry 4mm ply.

I made my first error here.  In an effort to speed up the process of cutting I screwed 3 sheets together.  This worked brilliantly when making the initial cuts but as I worked it more I found the screws pierced my fingers.  I struggled on having no shorter screws.  I then realised that I should have cut all 5 out at the same time...  The screws would have been fine then.

Anyway I got my clamps ready.

I made a little applicator from an offcut and spread the sheets with glue.

I clamped the lot onto a straight planed 2x2 wood beam to make an effort to keep it straight.  I didn't expect how much the sheets would slip as I clamped them and it needed a few adjustments before they were clamped and aligned.

I also found that the thin sheets didn't spread the clamping force that well requiring a few makeshift clamps to be employed.  This included the use of my oft-moched 1" vice.

So thats done, waiting time!

Pen to Paper

After messing about with the wheels it was time to make that all important template.  I drew it on 4 pieces of A4 selotaped together.

I am not 100% sure at this point what head angle to use, its drawn on as 20 degrees but the cut wood will have plenty of wiggle room.   I also changed my mind pre-cutting to extend the rear "subframe" so it reaches further back.  The frame will be laminated in two stages.  The first stage is to make the inner "core" of 3 sheets (so 12mm) that I will then remove material from to make it lighter (the holes in the picture).  I will then add 2 further sheets (one each side) making it 20mm thick.

The build begins (TZ 750 balance bike)

When we were little (2+) my Dad made my brother and I some little bikes, no pedals, suspension forks and little wooden engines.

Nowadays you would call them "balance bikes" but back then (the 70's) they were pretty unique.  I thought I would make one for my daughter.  Looking on the "net" people make them from plywood etc, 2 beams going from headstock to rear axle but they look a bit naff.

Having looked at a few bits of plywood I decided to make a replica of "The Kings" TZ750 flat tracker.  Just a bit of fun really and it will look different from the rest of the wood bikes making it a bit more worthwhile making the effort to make it. If I were just copying the design from others I might as well simply buy one from ebay (they are available new for around £30).

So, I popped to my local wood store and got 2 sheets of 4mm plywood (Far Eastern WBP).  These were a tenner (£10) each and came as a 8x4 foot sheets.  I had them cut each one into 2 4x4 sheets as I was in the car.  I also got some "external" use glue that is designed to brave the rain.

Now it was a windy day and it was with some trepidation I stepped beyond the threshold into the elements carrying 4 4x4 boards.  The timber shop was busy with tradesmen, keen to laugh at my newbie materials handling technique.  I needn't have worried, but I did have to bend the boards a fair bit individually to get them into my boot, this seemed to make a mochery of the guy who cut the boards for me remarking on how 'lovely and flat' they were...

Meanwhile, I had put a bid on a childs pushbike (12" wheels) on eBay and won it for £2.20!!  I picked it up, whipped the wheels off and threw the rest in the skip.

The wheels are a bit poor and need redoing so I nipped to my local cycle shop and got 32 new stainless nipples.

In fact while I was looking at them two fronts would be best as the rear is wider to account for the sprockets etc.  I set about removing the sprocket (helpfully welded on) and cutting down the axle to make it narrower. I may buy another bike just for its front wheel...

I have dismantled the wheels completely and plan to have the rims black, black spokes and polished nipples.   The front will have a black hub, the rear a polished one.  Should look pretty nice.