# Frugal trike frame project

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#### Frugal Flyer

##### Member
Hi all,
I am trying to build a low cost trike frame (although I plan to buy the wing), and before I could cut the first metal, I have already stalled with the rear suspension.

Here are the issues:

1. I have discarded the flat Grove type spring aluminum landing gear idea as too expensive and too difficult to make at home.
2. I have discarded the Tailwind/RV type round tapered steel rod type of landing gear idea as too expensive and too difficult to make at home.
3. I am still looking the Thorp T-18 and Drifter type tapered/stacked TUBULAR landing gear idea because they can be constructed (frugally) from straight tubes.

What I like on this third option are:

1. Tubes are straight, i.e., I don’t have to deal with bending.
2. I could use multiple sizes, multiple length tubes sliding into each other to simulate a tapered rod bending characteristic.
3. I could use multiple materials (aluminum, steel and fiberglass) to further tailor the stiffness/bending properties of the assembled gear leg.
4. I may be able to even eliminate the heat treatment (the remaining expensive part of the gear), if I can achieve the required strength, bending characteristic and flexibility without heat treating.

The questions that I still have:

1. I have figured out how to calculate the individual beam deflection on each of the cantilevered beams separately, but I don’t know how put them together, ie., how to to calculate the “tapered” beam when I slide the various diameter, various length tubes into each other.
2. Even if I figure out the formula, I still want to verify the deflection by test, but how?

a. I was thinking to secure one end of the gear leg in a hole drilled in a telephone pole and lift up with a carjack the other end to observe the bending characteristic (and eventually break it).
b. But how do I know that how much force I needed to bend it and how much needed to break it?
c. It appears to me, I need some kind of a load sensor on the top of my car jack that to attaches to a laptop, but I am not familiar with sensors.

Can someone have an idea how to find a low cost, easy to use method or sensor to measure the landing gear load up to about 5000 lbs?

(If someone knows the formula how to calculate the “tapered” rod consisting multiple diameter, multiple length, multiple wall thickness, multiple material tubes and maybe a solid fiberglass rod in the middle, I would take that too, but I I find an easy way to test it, I would just build/test/adjust/test until I am happy with the result.)

Especially interested to hear from “Head in the clouds” member, who seems to know a lot of the Drifter landing gear.

Thanks, Frugal Flyer

#### Andrew_J

##### Member
Hi, Flyer!
The best way to know how tapered rod consisting of multiple diameter, multiple length, multiple wall thickness, works is to make final element model (FEM) using any software (NASTRAN/PATRAN, FEMAP, SOLIDWORKS, ets).
It will be good to test FE model via the experiment you plan. To know the force the car jack generates you need to attach pressure gauge to it and to calculate jack piston area.
F=PxA
F-force, P-pressure, A-Area
The FE model is needed to understand how tubes of different diameters work together and how the output characteristics change if you change diameter, length etc.
Regards,
Andrew

#### Hugh Lorimer

##### Well-Known Member
One of the simplest trikes I have seen was in France, it consisted of, what looked like a length of scaffolding pole smoothly bent into a sort of "L" shape, no strut. U/C clamp mount doubled as engine and tank mounting. A simple triangular u/c seems to me to be the simplest and lightest way to go? Load it and drop test it, don't get too carried away with maths and science, remember the old adage "KISS" .............keep it simple stupid. Hughie.............

#### Hugh Lorimer

##### Well-Known Member
Straight tubes, nylon end plugs, pin jointed, one nights work?

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#### jedi

##### Well-Known Member
Some trikes have a solid gear, no suspension, and low pressure tires for shocks. Fiberglass rod is good spring gear. 1 & 1/2 inch OD solid rod can work. Won't break.

#### Matt G.

##### Well-Known Member
The FE model is needed to understand how tubes of different diameters work together and how the output characteristics change if you change diameter, length etc.
Regards,
Andrew

No, it's not...that would need nothing more than a spreadsheet.

#### Doggzilla

##### Well-Known Member
HBA Supporter
Personally, I would construct a swing arm with a torsion bar or leaf springs... and a dampener. ATV or motorcycle/scooter parts could be used very easily. The cost of any of these would be very low... And the leaf springs would allow you to adjust the amount of shock on landing to some degree by removing or replacing them... very cheap and reliable...

#### Frugal Flyer

##### Member
Hi all,

Although I was quiet, my mind was running ahead with full speed and here is the current progress report.

I put back the Grove type of landing gear on the table. The main problem was before that I could not figure out how to make it for LOW COST. What do I mean?
To do a Grove type of gear, one needs to be able to bend ¾” thick aluminum and that takes substantial amount of force, I guess at least 20 ton, preferably more. Well, up to 20 ton, the hydraulic jacks are reasonably priced, but over 20 ton, they get into hundreds of $. Typically anything over$100 is too expensive for me, but after some serious search, I was able to locate a 50 ton hydraulic jack for $50. So that will bend anything I need. Next problem was that one needs to build some kind of angle iron frame work to bend the leaf style landing gear. Well that needs a metal saw that I didn’t have. Aside from that, the trike itself likely will be built from aluminum and steel and fiberglass, therefore I needed a saw that can cut all of those materials. The problem was that there are typically two type of saws out there, the standard miter saws that Home Depot sells to cut wood, aluminum, those running on 3000-4000 rpm, too fast to cut steel. Than they sell the chop off saws to cut steel, but those are inaccurate and cuts too hot. Anyway, being frugal I was reluctant to buy 2 saws, so I searched more and I found what they call “cold saw” or “multi saw”, that runs around 1400 rpm and cuts steel, aluminum, wood, cuts it all. I purchased the 14” Evolution Rage 2 saw from Amazon at$262 because it is almost $100 cheaper than the next cheapest option the Dewalt DW872. It cuts to about 5” material, so that should be enough to build any part of the trike or the material for the Grove type of landing gear bending fixture. I still have to figure out how to deal with the heat treatment of 7075 aluminum, but that will come later. So all that gave me a second option for the rear landing gear beside the Drifter/Thorp T-18 style tubular landing gear. I also progressed in my mind, how to test my landing gear, and specifically how much force it gets during testing. Since now I have a 50 ton jack, I can bend/break whatever I make, but at what force? What I came up with following Andrew_J suggestion (after unable to find low cost crane scale) is to screw into the hydraulic jack a$20 pressure gage from McMaster, so I can measure the force on it during testing. So for less than $100, I can now measure the force on the 50 ton jack during testing. I am happy with that. As far as the trike landing gear, I want to design it to the 1320lbs LSA limit, test it to 3g (to simulate hard landing) without any problem, and 6g (to simulate crash landing) when it should bend permanently to absorb some of the shock. The problem is I am not certain, what actual test load do I need? If I understand, 75% of the g force should be applied downwards, 25% forward to simulate the landing. Does that mean I need to load the landing gear with 2970lbs for 3g and 5940lbs downwards for a 6 g test? Also since a picture worth 1000 words, I put up a few of the potential landing gear configurations. The first one is the typical triangulated trike landing gear that I don’t like because too draggy, too complex, needs an (expensive) shock, but I put it up for reference anyway. The second one is from a trike Antares, typical Grove style simple, strong leaf spring. The third one is from a trike named Tukan. I like the simplicity of the tapered rod effect created by the various tubes inserted into each other, but can I make it strong enough? I think I can, but the test will have the final word. So in summary, I have bought some tools, some materials, figured out in theory how will I test landing gears and now ready to build something. Remaining issues: 1. Do I have the correct load for 3g and 6g testing? 2. How do I heat treat 7075 Aluminum (the frugal way)? …until next time... Last edited: #### jedi ##### Well-Known Member Plans for a simple trike are available free on the internet. Anbody remember the name off hand or have a URL. It looks like the third photo above. If a simple and cheep one off is the goal you are over achieving. #### BoKu ##### Pundit HBA Supporter ...screw into the hydraulic jack a$20 pressure gage from McMaster, so I can measure the force on it during testing...
I've built and used a force measurement system using a harbor freight pullback ram and a hydraulic pressure gauge. I used this device to test rock climbing gear and also sling and cordage knots and configurations. Yes, it can be made to work, but there are some caveats:

* You must know the effective piston area in order to translate the hydraulic pressure into force. Of course, A=pi*r^2, but you should not assume that the effective piston diameter is the same as the diameter of the shaft that extends out of the jack. For most bottle jacks I've disassembled, the piston inside the body of the jack has a greater diameter than the shaft.

* The piston seals have a great deal of sticktion, so the measurements will not be very precise. When I tried to calibrate my device against an electronic load cell, I found that there was a lot of hysteresis that made it impossible to calibrate to any precision. So what I ended up doing was buying a simple 10,000 lb load cell and digital readout on eBay. Problem solved!

Personally, I think that I would make the landing gear in the VariEZ style, with many plies of unidirectional fiberglass. The materials are fairly inexpensive, the processes are well understood, and the finished product can be tuned by adjusting the width.

Thanks, Bob K.

#### Frugal Flyer

##### Member
Jedi.

Plans for a simple trike are available free on the internet. Anybody remember the name off hand or have a URL. It looks like the third photo above. If a simple and cheep one off is the goal you are over achieving.
I am aware of at least 3 available trike plans. I have two of them.
HTML:
http://www.airtrikes.net/introduction.shtml
The Tukan is the other one, but it only has a Yahoo group. The problem is that none of them meets my "mission" goals.

Having said "mission goals", I am now obligated to explain it for future reference. I would like the ability to fly 500-1000 miles non-stop at up to 80 mph cruising speed and take off/land off-airport. That needs about 40 gallon gas and least an 80 hp engine and a very strong suspension. I would like to keep the trike cost under $10k even though I am aware of the current engine prices (therefore an 80 hp VW is likely the only engine that is usable for me for around$4k).

I am trying to address a few specific issues too. I need high ground clearance for off-road landing. The Airtrike does not have it but the other 2 have it. I would like to distribute the gas in 10 gallon removable tanks, so I can take them to gas station to fill up if I have to. Some Antares model comes with 40 gallon tank, but those are built into the trike, so one can't carry them to a gas station. And I am trying to make the trike field reparable (bolted instead of welded structure) for obvious reasons. Also since I plan to use the trike sometimes just to get somewhere, sometimes for camping, sometimes I prefer the (fiberglass cockpit) fairing, sometimes not, so it has to be easily removable.

The typical flying would be from San Francisco to Portland where I have friends, San Francisco to LA where are more trikers, up to the Sierra, and exploring the Western United States particularly the Southwest, Utah, Arizona, New Mexico by "trike camping" (instead of car camping), so fuel economy is important (another reason why 2-cycle engines are out).

Given my goals, most factory trikes with 4 cycle engines are out of my budget, since the typical Rotax 912 is over $20k. I see trikes with 2 cycle engines as low as a few thousand$, but none of those built strong enough for 4 cycle engines. Primarily they are built from Aluminum, versus many of the 2 seater Rotax 912 trikes built from welded 4130 steel structure.

So hopefully the above description will give some idea, why I am not looking for the cheaper light duty 2 cycle trikes and why, and why I don't want to buy the heavy duty factory trike with 4 cycle engines (even if I could afford them).

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#### Frugal Flyer

##### Member
So what I ended up doing was buying a simple 10,000 lb load cell and digital readout on eBay.
Bob,

Do you still have some kind of lead/info on that 10,000 lb load cell? Manufacturer, web link, etc. It is an interesting idea if it is cheap enough.

Personally, I think that I would make the landing gear in the VariEZ style, with many plies of unidirectional fiberglass. The materials are fairly inexpensive, the processes are well understood, and the finished product can be tuned by adjusting the width.
I still prefer the tubular landing gear shown on the right side picture for 2 reasons:

1. It is field repairable.
2. It can be modified relatively easily to be retractable.

However, do you have a good link for description to build VariEz style landing gear? (Because I thought that those are exclusively built by specialized people for sale, I didn't think, those are for home builders).

#### BoKu

##### Pundit
HBA Supporter
Bob,

Do you still have some kind of lead/info on that 10,000 lb load cell? Manufacturer, web link, etc. It is an interesting idea if it is cheap enough.