Project Drypod

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Oct 19, 2012
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This thread will document my efforts to make a covered trike. The design brief is:-
  1. Practicality - it has to be easy to get in and out of, carry some shopping, be at least as comfortable as the average vehicle like this can be and keep the bulk of the weather off. It do not expect it to be as dry as a car.
  2. The lard has to be kept down. I have to have some hope of pedalling it without a functional electric assist. With a decent hub motor and 48v battery it'll never be any featherweight but I'm setting a target of sub 50KG with the electrics on. No mega expensive parts will be used. Weight saving can not be at the expense of point 1.
Here's my working designs:-





There'll be a door on one side only. The side windows will run in double channel and will slide like an old Land Rover. Made out of 2mm polycarbonate they'll easily bend enough to get in the channel or take out completely if the weather allows. The windscreen will again be 2mm polycarbonate and will be curved to encourage the rain to run off. The windscreen and roof will overhang the door slightly again to encourage rain and wind not to worm it's way inside. The chassis will be 40x20x1.5 steel and will be the traditional T shape. No front suspension as it'd just add too much weight but there is suspension on the rear. Front wheels are very skinny 20" and the rear will be a 28" hub motored affair. The body frame will be aluminium as it'll be unstressed. At least it'll be unstressed unless and until the steel chassis asks it to help out. This is an area I can't fully resolve as the two have to be connected and steel is just way too heavy so I'll probably use some rubber washers between the two to keep the ally as unstressed as possible. Body panels will be correx bolted to an ally 15x15x1 square aluminium frame via nylon bolts to keep weight down. I wanted to use aluminium angle as it's lighter and it makes door to frame overlaps much easier but I came to the conclusion it simply wasn't butch enough unless it was actually heavier than the square tube. There'll be a correx floor on the underside of the frame and an expanded aluminium mesh floor above that to catch my feet if they head that way. The mesh won't hold my entire weight but should easily cope with getting in or out mishaps that would otherwise see me with a Flintstone's vehicle. The same expanded mesh / correx combo will also serve as a floor in the luggage area at the back. Access to the cargo area will be only over the back of the seat. Less practical than an opening hatch I know and the first instance of me breaking my own rule before I've even started :whistle: but it's a big help in keeping water out! Brakes will be mechanical discs all round. Gears will be 3x8 as I've got a lovely pair of Deore LX 3x8 brake levers / trigger shifters just begging for a role.

There's a lot I'll have to engineer on the fly here and I'll need to learn how to solder aluminium to make the body frame. If I get it right the Drypod will just fit me in with very little room to spare. My fat trike is coming to a conclusion soon and this will be the next project in the garage. It's easily my most ambitious to date and thus comes with the most and tallest hurdles.
 
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Last week I looked ad a few bikes that are similar but than as quad.
Here some images.


I like the looks of the first one, but I think that the second one is more what you want.
 
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Have you seen these ?

Mr Mcgroovys rivets ?





They are made for making kids toys from cardboard boxes but I understand will work on correx and are light , rust free and reusable ?
 
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Winnipeg, Manitoba
I will for sure be watching this build with a lot of interest. Your plans sound a lot like what I was aiming for when I built my fat covered trike. Good luck on the build.
 
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Oct 19, 2012
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The push fit fasteners are a good idea. I'll give that one some thought. Would be even lighter than nylon bolts.

Edit
On consideration almost all these push fit fasteners have heads that are too big. The frame is only 15mm square so that would be the max size of the head assuming I drill perfectly central for many dozens of times. I could deliberately offset drill to keep the head from jutting out I suppose. In reality I'd like a max of 12mm and very few get that small. At the moment I'm still intending to use nylon bolts. The heads of them are relatively small so will be unlikely to poke beyond the frame. They also are likely to give me more peace of mind than push fit.
 
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Uprights and front axle made. I ran out of CO2 without spotting it until too late as I finished the axle so will need to grind and redo tomorrow. Worse things have happened. Most of the old timers here will be aware of this alignment idea (I got it from one of Emma's posts) but for the benefit of those who aren't a length of threaded rod can be used to align the front wheels and uprights before attaching them to any part of the chassis - in this case the front axle. This keeps the wheels well aligned at least against each other. The track is set at 800mm wheel centre to wheel centre. It's a little bit wider than most taddies because this will be a little higher than many so the extra track offers some extra stability. I've tried to keep the uprights as small and compact as possible (ie light). I'm again using split flanged PTFE lined bearings for the kingpins. A matched pair (ie proper left and right) of mechanical callipers will mount to those brackets. I made those wheels a few months ago now. I came across them on ebay just as I was considering this project and thought an overall orange colour scheme would be nice and visible. They're very skinny and run a 12mm axle, again to keep weight down to a minimum. They aren't going to offer much in the way of comfort but the seat I've chosen will take care of that. Tomorrow will hopefully see the rest of the chassis and rear swing arm in place.





 
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Main chassis member, rear wheel, suspension and seat in. The seat is a concession to weight. With no front suspension and minimal tyres a padded seat is a necessity. It weighs in at 4kg. I could have got a lighter one but it looked awful. The seat looks well out of place at the moment. Hopefully it will look more at home when I get the bodywork around it. The rear wheel is a 27.5 and is just holding the space for a 28" hub motor.

 
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Bottom bracket, steering and chain management in. I'm using a M10 rod end as the bottom steering pivot and a 25mm diameter tube will weld to the top of the penny washer under the button head bolt to make the column. I can't weld the bottom mount bracket yet as I don't know where the top mount is going to be. The top mount joins to the body frame under the windscreen and is the only structural load the body frame should take bar it's own weight. Once the top mount is fixed I can then fix the bottom and will have no universal joints in it which will keep weight down and keep the steering lighter. The top mount will be a split collar with only one half fixed to the frame so I can get it on and off. That's about it for the chassis parts, bar the mounts for the body frame so tomorrow it's the start of the great aluminium soldering experience.



 
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Soldering has gone badly to be polite about it.:(

I tried nearly 50 joints and cleaned and cleaned but to no avail. Every joint was far too easy to break. Most of the joints looked good and the solder flowed well but offered poor strength. Going to steel would add over 8kg so that really is a last resort. I'm currently having a go with 21.5mm waste pipe with various joints and a very pungent solvent based glue. I can drill a hole with a 22mm hole saw in the joints to add extra pipes and have apparent success with my first effort at such. The glue in question physically melts the pipe together so there should be no worries there. Initial efforts have given me a curve I can live with and all other bits are straight bar the screen formers. I'll persevere with this for now and see if I can get an acceptable frame with it. Hanging the steering column from this doesn't seem a good idea at the moment so if necessary I'll have to brace it by extending the front mech post and also bracing vertically down to the main chassis rail. I'll see how rigid the frame is before committing.

 
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Getting there:-







Quite pleased with how it's progressing. The joints are easy to drill with a hole saw to add extra tubes:-



The rear cantilever for the cargo area looks a little want to pull itself off the rest of the frame so I propose to run two tensioned wires as per this.....



... to hold the lot together. It's the sort of thing I've seen on Grand Designs so if it'll hold a building up it should hold some groceries.

There is an oops moment here in that the frame wants the same space as the steering. Not my worst ever failure. I'll just have to raise the steering arms.



I've still to make the door and the opposite side window aperture plus the mounts for the frame. I've also still to make the windscreen forming curves. This waste pipe is a doddle to work with and the specialist solvent gives you about 10 seconds to get alignment before it becomes reassuringly solid. It actually melts the plastic so as to weld it together.
 
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Wouldn't it be better to carry the luggage both side here ?



Where it is lower down to aid stability and does not need all that extra bracing ?

Where does you head come ? it looks a little tall , unless you seat is short ?
 
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You're right about it looking tall. There's a good 6" of headroom at the moment because I intend to raise the seat at least 4". Initial pedalling efforts had me too folded for comfort and raising my backside will ease that. It'll also help in getting in and out and practicallity is high on the design requirements. I've changed my mind on the bracing and will use 6 lengths of m4 studding as the bracing as I'm not convinced cables won't stretch. Only catastrophic frame failure will fail to hold then.

Putting cargo there would have it in an awkward to reach place unless that section was totally detachable. One of the main reasons for the current cargo area choice was ease of use plus the whole area acts as an aerodynamic aid in reducing the abrupt termination of the bodywork. I further intend to partially panel the section under the cargo area in a line from the corner at the bottom of the seat to the bottom of the rear square. The only weight that'll add is the weight of the correx required to do it. It'll still allow easy access the the rear wheel but should further aid aerodynamics.
 
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Putting cargo there would have it in an awkward to reach place unless that section was totally detachable.
I was more thinking of accessing it from the outside on each side ?

Maybe have the side tip outwards like a chute ? and it would probably then auto close with the weight inside it ?

Paul
 
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A chute or two would be practical but would likely add a fair bit of weight. Given that I wanted the tapering body over the back wheel for streamlining anyway it makes sense to use that. I can see that that space will have a weight limit being cantilevered and the strengthening studding will help greatly there. I'll revisit your idea as plan B should the existing area not show itself to be acceptable in that regard. The top of the bottom (if that makes sense) ie the top of the bottom tubes of that cargo area will be furnished with an aluminium expanded mesh as a light but strong floor and this should also add some strength if I can convince the glue to bond aluminium to the tubing. Correx will keep the crud out from underneath those same tubes.

Having given a little more thought to reinforcement I'll now add 8xM4 studding from immediately behind the seat, over the back and forward to the screen. It's the easiest thing in the world to add more weight and this studding will add near as damn it 1kg. This can be absorbed because the frame is actually lighter than I had bargained for in aluminium.

I'm aware I'm hardly the first to use waste pipe as a frame but I'd just like to state how easy it is to work with for this task. I appreciate it's very early days but it does seem very suitable for such a job. One word of warning though I know PVC pipe is not UV stable and will get brittle with age but that issue will be many years down the line. I've just replaced an external waste pipe that crumbled after 30 years. It wasn't under any stress at all and if it was it may have crumbled in half that time or less. I think that pipe has got better in that regard since then as I also have some 18 year old external pipe which is showing no signs of failure even by deliberately flexing it.
 
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Seat raised about 3". I now have 3" of headroom. A little more or a little less depending on how I slouch. Doubtless some effort on the pedals will have my upper half pushed upwards somewhat so there's room to spare. The observant among you will notice a large piece of extra chassis.



The extra chassis pained me to put in but on moving the seat base up I noticed the sole member was bowing quite noticeably. It's the same 40x20x1.5 I've made most of my chassis out of but this one is longer and the extra length was simply too much to withstand my lard. Extra metal therefore had to go in. Not only does it make a nice triangle but the seat is also tied to both members making them both take the weight. It doesn't help access and egress but it's not too much issue to work around. The astute out there will notice that this new member wants the same space as the steering column will require. No worries there as when I can see exactly which bit of that new member interferes with the column I'll chop it out and weld some heavy pipe in to make a circle for the column to pass through. It'll weaken the new member unless the pipe is sufficiently robust to stay round.

The door is half made. I frankly gave up for today as the new steel roof on the garage does not help in cooling it. I need to make some corner fillets out of some sheet aluminium and pop rivet them on to assist in it keeping shape. I need to make a window track and I need to hang the door. I also need to then make a latching mechanism. It might also require a diagonal pipe to help keep shape too. Perhaps the door is only 10% made not half 😢.



 
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I've not done anything with this for a few weeks because I've hit an impasse. The plastic frame is fine for holding itself and any panelling but it's just not going to hold any cargo in the cargo area. Despite the strengthening studding the frame simply has no strength for the task. I couldn't even put the (smallish) 48V battery there without risk of failure. Also getting a fairly flat panel such a a door to hold a shape is proving difficult. I think I can overcome the latter but the former seems insurmountable. That leaves me with four options. If you can see more please chip in.

  1. I accept that it will never hold any shopping and press on. Practicality was my no.1 aim and no cargo equals a lack of it so I'm not favouring this option at all.
  2. I fall back on good old steel for the frame. Welded steel is certainly strong enough but this will add a minimum of 6kg and realistically nearer 8kg which in my mind is pushing it into something I'd never want to pedal without the motor chipping in. Bear in mind it was never going to be light in terms of a trike but now looks like my 50kg target has no chance of being met and I was marginal on practicality without this extra weight. Again practicality is slipping away.
  3. Complete redesign to get cargo space down on the chassis. I've so far drawn a blank on anything both practical, possible for me to build and is aesthetically pleasing.
  4. Abandon ship and use the components for something-else.
I thought of just using steel where needed but the whole frame carries the load hence my efforts with the studding and therefore it's not a starter.
 
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What sort of weight do you envisage carrying ?

A simple pannier frame either side of the rear wheel should not weigh 6Kg ?

or make a pannier frame cantilevered off rear of seat
 
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Just a couple of large bags of shopping. Yes I could use the rear swing arm as a cargo carrier. This particular one is aluminium so modifying it will pose problems but it's not a major issue to get a steel one. I could then considerably shorten the rear bodywork to provide only some streamlining and avoid a blunt termination of the bodywork which would even get a bit of weight back (not much but it all counts). That's a good idea Paul. Thanks. I'll give it some consideration. I'll also work a bit more on the door problem. I think I can solve that by overbending the door, putting some aluminium bar across each corner and pulling the door tight against those stops.
 
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Popshot: I see you are experiencing difficulties similar to those I experienced before I shelved my eLecTricks Tadpole build in favour of a delta recently: The bracing requirements for various things that must hang in cantilever fashion from the forward frame. This is compounded if you have rear suspension that must be free to move, leaving all cargo carrying support to come from further forward.

Just a suggestion: Can you use aluminium infill panels for a degree of cross bracing and/or panels? Might require the replacement of a plastic strut or two with steel though.
 
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