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 Post subject: Re: Reverse trike build
 Post Posted: Mon Apr 03, 2017 9:54 pm 
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Joined: Fri Jan 13, 2017 11:42 am
Posts: 28
This is the jig turned over for the much smaller upper wishbones. The ball joint housing for the Gemini upright (not shown) is an odd-sized M17x1.5mm. I bought a suitable tap and 15.5mm drill off Ebay, found some 5/8 inch connector nuts (similar to a standard nut but 50mm long) at Bunnings and redrilled and tapped these to accommodate the ball joints. What was rapidly turning into a nightmare was solved easily using these bits. I happened to have some 5/8 inch SS nuts, and once altered as above made good locknuts for the balljoints.
Would have been much easier if I'd still had my lathe, but I sold that off prior to a move to a smaller home, which never eventuated, so luckily I've still got my shed. I cancelled my BOC bottle accounts too and sent back my argon, oxy and acetylene bottles. So for this job I bought a bottle of argon outright, no more horror rental charges, and cheap to refill.

I have a basic no-frills tig welder which I've owned for 15 years or more. It's ok, does the job, but makes life that little bit harder than a better machine would.


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Last edited by LoGo Trikes on Tue Apr 04, 2017 9:07 pm, edited 1 time in total.
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 Post subject: Re: Reverse trike build
 Post Posted: Mon Apr 03, 2017 10:15 pm 
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The two upper wishbones. I had to play a flame on the joints and pull and tug a bit to make things line up properly because despite best efforts the welds tend to pull things out of square. All ok. The welds on the connector nuts are a bit untidy which I wasn't happy about, but I've seen worse, and a small welder like mine gets out of shape on thick metal...


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 Post subject: Re: Reverse trike build
 Post Posted: Mon Apr 03, 2017 10:24 pm 
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Joined: Fri Jan 13, 2017 11:42 am
Posts: 28
This one of the lower wishbones cable tied to the frame to see how the brackets lie. I wanted 4mm steel but couldn't find any. I used 5mm in the end and as you can see, they're a bit overkill. 3mm to my mind isn't thick enough especially on the lower wishbones. 5mm thick brackets will mean that the bolt holes are less likely to go oval over time. The bottom brackets are doing most of the work, so I included a small return underneath to prevent any deformation under load. Probably not needed but...


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Last edited by LoGo Trikes on Tue Apr 11, 2017 3:17 pm, edited 1 time in total.
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 Post subject: Re: Reverse trike build
 Post Posted: Mon Apr 03, 2017 10:28 pm 
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Joined: Fri Jan 13, 2017 11:42 am
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Another view of the lower wishbone mounts prior to tacking in place...

I've since found that the smaller diagonal tube is just in the way of the rack, so they'll have to go dammit. Had I known how close it was going to be, all I had to do was slide the mounts toward the rear of the frame by 12mm or so and the rack would be clear. But then I would have had a problem welding the last bracket. There was little enough room as it was. Some of the problems of designing on the fly...


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 Post subject: Re: Reverse trike build
 Post Posted: Mon Apr 03, 2017 10:39 pm 
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Got there in the end, but welding the outside of the rear bracket was a real test; there's another tube close. There have been a few spots on the frame like this and there will be a few more I'm sure. Tig welding is all about a steady hand, and, where the access is good with somewhere to rest the torch hand and swing through the length of the weld without repositioning, anyone can turn out half-decent welds like these...

Actually the front weld looks a bit odd in this picture; the scallops don't look right, but in the flesh looks entirely different, better different. See, the camera does lie...


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Last edited by LoGo Trikes on Tue Apr 04, 2017 10:20 pm, edited 3 times in total.
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 Post subject: Re: Reverse trike build
 Post Posted: Mon Apr 03, 2017 10:51 pm 
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Posts: 28
Trying the upper wishbones. I've yet to add in a couple of washers either side of the blue bushes on the top wishbones to give me a degree or so of extra or less caster, and I'll adjust the length of the crush tubes accordingly. Crush tubes, as their name implies prevent over-tightening of the bush housing bolts. They are made slightly shorter than the overall length of the bush housing plus the blue bushes, in this case around 50mm wide. Being slightly shorter than the overall length of the bush tube allows the blue bushes to slightly compress to give a small resistance. I chose 40mm width for the bush tubes, so that 40mm plus the lips on the bushes, plus the width of the brackets equals 60mm all up. A washer at either end of the bolt all adds up to 62mm or less, so I can use a 75mm bolt leaving 13mm or so for the nylok nut. Should be ok.

Only use HT bolts at least 8.8 hardness...no stainless steel no matter how appealing that might be, or titanium for that matter. They won't pass inspection. SS fasteners can only be used in non-critical areas. Any fastenings to do with steering, suspension and the pedal box can be considered as "Jesus" fastenings, so particular attention must be paid in these areas. For the sake of making the wishbones in the jig and bolting the suspension together I used ordinary cheap bolts from Bunnings, but these will be substituted for the correct fasteners when the time comes.


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Last edited by LoGo Trikes on Tue Apr 18, 2017 1:08 am, edited 4 times in total.
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 Post subject: Re: Reverse trike build
 Post Posted: Mon Apr 03, 2017 11:00 pm 
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Posts: 28
I went for 8 degrees of caster. A light rear-engined vehicle has little mass at the front and needs a fair amount of caster, anywhere between say 7 and 10 degrees. The more caster built in makes turning the front wheels harder, but gives snappier self-centering, and I'm all about good self-centering and plenty of it. The mount for the protractor is jimmy rigged but I'm sure its ok, and in any case was duplicated exactly on the other side, so caster on both sides should be the same whatever it happens to be...

I also tidied up the ends of the lower wishbones. Some builders leave them open but I thought that an end piece makes the mount stronger. Looks a bit neater too for a tiny weight penalty.

Google has plenty of info on positive caster and how this essential design element applies to steering. Basically as you turn the steering wheel the axle has to climb out of a gully, where it sits in the straight ahead position, up a hill as it pivots the road wheel, bit like the rising hinges on doors that self-close. The axle constantly wants to slide back down again. Its default preference is to stay at the bottom of the gully thanks very much, until forced up the hill. The steeper the hill, ie the more degrees of backwards-leaning positive caster, the more force required on the steering wheel, but the axle will slide back down again quicker once the force is removed, and want to stay there, in the gully, pointing the front wheels directly ahead. As you turn into a corner, you're applying the effects of caster, and as you exit the corner, anyone who drives a car will have noticed that hardly any effort is required for the front wheels to want to return to the straight ahead position.. the steering "self-centres," and you can "slip" the steering wheel through your hands rather than have to deliberately turn the steering wheel back to a central position. It's not what a driving instructor will want you to do when learning though. He'd rather have you feed the steering wheel back in increments, so you always have full control. Not altogether necessary in my view.

Racing car drivers, F1 etc have such "quick" steering that they can steer from lock to lock without their hands leaving the wheel. Much like go-kart steering. Us lesser mortals however have to make do with slower steering, usually 2.3 up to 2.9 turns lock to lock. Besides, my old brain and reflexes just aren't up to the demands of very quick steering, so until I know better, or my reaction times and reflexes are better than I think they are, which is doubtful, I'm going for a rack with 2.9 turns lock to lock. Which means essentially that I won't be doing any track work, just the highways and byways of our wonderful country...

With power steering the force required to turn the steering wheel is largely irrelevant, and in any case the degree of caster on mass produced road vehicles is mild compared with what's needed for this application, perhaps 5 degrees.

You must have at least some caster. No caster at all means that the front wheels will want to wander all over the shop. There is no gully for the axle to sit at the bottom of, just a flat plane, and the front wheels can go where they wish, reacting strongly to changing road surfaces, road camber, bumps, potholes etc. Not at all safe, especially at high speed, so for me, I want plenty.





Don't confuse 'caster' with 'camber,' an entirely different animal. I'll talk about that later....


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Last edited by LoGo Trikes on Tue Apr 18, 2017 1:19 am, edited 12 times in total.
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 Post subject: Re: Reverse trike build
 Post Posted: Mon Apr 03, 2017 11:16 pm 
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Posts: 28
This is as far as I've got by 3rd April. I probably wont be doing much more for a few weeks, but stay tooned...

Next up will be the front shocks which will probably be "Protech" shocks from the UK. 330mm eye to eye. 9 inch springs rated at 225lbs. Even though the open length is 330mm I'll need to compress them probably down to 300m or so when mounted. This aspect is very hit and miss as to exactly how much to compress the shocks prior to mounting and may need some playing around with when the chassis is on wheels near to its kerb weight, so for the time being I'll only tack the top mount brackets in place, ready to move them around if required.

EDIT. I've since found out that the accepted practice is to position the wishbones at ride height, and halve the distance between open and closed length of the shock. Say the difference is 100mm, then half is 50mm. So, at ride height the shock should be compressed 50mm. This obviously gives 50m of droop and 50mm of bump. Easy now I thought about it a bit. I might also make the suspension by "push rod and bell crank" instead of the conventional practice of mounting the shock between the lower wishbone and frame, which is much easier but limits the amount of adjustment available. Pushrod and bell crank while being more complex, expensive and harder to get right might be forced on me by the design of the lower wishbone being extra long, and the upper wishbone narrower than I should have made it, making a conventional shock mounting too difficult to squeeze in. I could make wider upper wishbones, but I don't think width is enough on its own. I'm certain the spring will foul the upper wishbone on droop. Bump is ok, but I've done some rough measurements on droop and it's too close. You might notice that Indicars have this type of rod and crank suspension because the wheelbase is very wide and the body narrow, ie the same problem I have. There are marginal benefits to pushrod suspension; less unsprung weight and a small aerodynamic gain. There's also the wank factor of having the exposed shocks at the top of the vehicle a la Ariel Atom. So this is probably the way forward...

After this edit, much of the following still applies because the pushrod is doing much the same job as a shock does in the conventional position, even though the shock will now be mounted elsewhere and actuated by a bell crank. The bell crank can have several pushrod mounting holes to make the suspension hard or soft depending on the throw of the crank. The throw isn't linear, rather it's logarithmic, but that's maths for another day cos it makes my brain hurt, and isn't needed for this application. Well, it might be but luckily I came across a paper some dude had written for his BSc for exactly this application, and all the measurements, diagrams and formulae are there in the public domain for me to pinch, saving me much head scratching. If I can contact the guy I should ask for permission to use his work I guess...

The UK Tr1ke has 175lb springs, with a shock lean angle of around 30 degrees, so using a special formula gives the effective spring rate at 30 degrees of 152lbs. It's called a "spring rate correction factor" and although there is some easy math involved to calculate the effective spring rate versus shock lean angle, all the math is presented as an easy to follow table. (Google "coil over spring rate correction factor", go to images, and there are lots of examples of the same formula. My springs (or pushrods if I go that way) will lean in at around 45 degrees, so using the same formula I arrived at an effective spring rate of 159.75lbs, pretty close to the Tr1ke's 152. Taking into account that my fuel tank will be at the front (or may not if I use the Kwaka tank in situ), and not at the rear like the Tr1ke, I think 159lbs should be ok. I can adjust the ride height in any case so it should all work out ok. I can always substitute different spring rates later. Protech springs aren't expensive., maybe go up to 250lb springs, we'll see...

ACF (angle correction factor)=cosine of the lean angle degrees. For example 45 degrees lean angle gives .71, so 225lb spring x .71=159.75lbs. (250lbs gives ACF of 177.5lbs) and so on for other lean angles.

I must start thinking about the steering column. I've got a Gemini column lined up, but not given much thought yet about the positioning of the rack and column. I can't think about mounting the steering column until the driver's seat is in place. The rack will probably be a Ford Sierra, which I can buy new from the UK. An Escort rack is the usual suspect but the Sierra rack is wider and to my mind has better mounting points, more amenable to adjustment than the Escort rack mounting points.

Also, somewhere at the front, but well-protected, I've got to find room for a decent-sized fuel tank, about 40 litres. I've got some thoughts, and a few candidates lined up, but a lot depends where the pedal box will be, and I won't know that till I've got the driver's seat in place. EDIT. This might not be necessary, read on...

The chassis and wishbones are now set at the correct ride height, and this will help me determine how the ZX14 engine and rear end will sit. I can plan an extension to the jig to accommodate the rear wheel and where the motor will sit as a part of the rear chassis seat set back.

I'm still inclined towards mounting the motor complete with frame, fuel tank etc. I've been advised against this though because it will mean the fuel tank and therefore the centre of gravity will be higher, reducing cornering ability and the stability of the trike. The objection is a good one and well-founded, but there exists the Mako trike which is thus equipped and seems to be more than stable on the track. On the debit side, the wheelbase is then longer which isn't such a good thing in my case.

The advantage of using the existing ZX14 frame and fuel tank is that there is no fooling around with all the plumbing involved with a separate fuel supply, no surge tank required, and the frame supports the fuel tank, the EFI, air box, fuel lines, much of the wiring etc unmolested. Importantly, using the frame also means that the rear suspension pivot stays in place and means less buggering around locating the rear suspension pivot as part of the chassis frame. Saves a lot of design frustration. Sounds like a win-win, and would make life much easier. Reduced fuel load however of around 20 litres. Good for a few hundred kms between stops probably. I might keep the radiator in its correct place too, but then I'll need to ensure good air flow. That's a tough one, but doable. Dunno, I'll cogitate on all these things...

Basically, what I need to do is take the Kawasaki ZX14, remove the front forks, front wheel and brakes, fairings, seat etc, and bolt the frame steering tube on to the rear of the chassis behind the seats, add a few brace tubes, and voila the job's done. Not as simple as that but that's it in essence...

Initially the ride height was set at 135mm, Later this was amended to 150mm, the reason being that we have a rising driveway with a brow hump onto the road which even a standard car sometimes bottoms out on if fully loaded. The house sits about 8 feet below street level and a brow hump was set in place when the drive was laid to prevent rainwater washing down the drive from the road and floating the house away. It's this bit that's hard to get over. I'll need to enter and exit the drive at an angle to ensure this new car doesn't bottom out, which is what I had to do with the Lotus, and even then I'm not sure this new chassis will make it over without severely scraping the bottom. I don't know if 3 wheels will be easier than 4 in this case. Find out at the time I guess. This will be a long-wheelbase car, can't get around that, so I might have to add some plastic rubbing strips to the bottom of the chassis and approach the brow at a lick to get it over. It's a really bad piece of real estate, and I've even thought of reducing the height of the brow somewhat by planing off a bit of the concrete with a grinder and then repaint. That might work. I could easily shave off a couple of inches, which could make the difference between going out for a fang, and going nowhere...


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 Post subject: Re: Reverse trike build
 Post Posted: Mon May 22, 2017 4:25 pm 
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Joined: Fri Jan 13, 2017 11:42 am
Posts: 28
Next, the suspension..


Last edited by LoGo Trikes on Mon May 22, 2017 4:42 pm, edited 1 time in total.

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 Post subject: Re: Reverse trike build
 Post Posted: Mon May 22, 2017 4:34 pm 
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Joined: Fri Jan 13, 2017 11:42 am
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Think I've figured out how to do the front suspension. Going with the Atom design, or similar to it, at least till I change my mind... Here's the start...

I probably wont use pieces of brick in the suspension. I used a piece of old 3/4 4130 for the 45 degree angle needed for the pushrod. I'll be using the same stuff but with 156 thou wall thickness so I can tap the ends 1/2 inch UNF to accept the rod ends without having to fanny around welding threaded bungs on each end. This thick wall means a bit of extra unsprung weight but I'm not too concerned. I'll draw up something full size so I can plot exactly where the bell cranks will be positioned..

To the far left of the picture I've removed the diagonal square tubing, which would very likely interfere with the steering rack, and made up some flat 5mm brackets with holes in which I've tacked in place to hold the front end square. I'm getting a bit low on argon, so until I refill the bottle the argon can be better used elsewhere...


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