Progress report for ONE21-381
Project Information
This project seeks to reduce repetitive and non-creative tasks through the use of an open-source High Tunnel Gantry System (HTGS) with two implements; a Transport Cart and Automated Row Cover System (ARCS).
- Design. We will develop a HTGS design plan. The design will include the rail, toolbar, trolley car, Transport Cart, and ARCS. We will engage farmers during the design process to inform the design and educate farms on design considerations.
- Build & Evaluate. We will construct a fully functional HTGS. We evaluate the implements for functionality, ease of construction, and ease of use. We will create videos of the installation and testing process to assist other farms adopting the system.
- Research. We will quantify the labor savings of the Transport Cart and ARCS through two labor studies. We will collect labor data during peak season and compare it to a similar control environment. We will write a report detailing our findings.
- Education & Adoption. We will publish the designs, reports, and videos on our website and open-source tool design website, farmhack.org. We will host two on-farm workshops and publish demonstration videos. We will present the research findings, use-cases, installation, and best practices at the 2022 NOFA-VT and NEFVC conferences.
Repetitive, laborious, and non-creative tasks hinder small farm profitability, scalability, and innovation. Labor costs are typically the largest expense for sustainable farms. Finding and keeping reliable help is increasingly challenging and hinders farms from sustainably scaling operations.
Farmers are increasingly growing in high tunnels in the Northeast. High tunnels help farmers extend their growing season, improve plant and soil quality, reduce nutrient loss, and reduce energy use (“High...”, (n.d.)). Since 2002, there has been a 3.5x increase in small vegetable production greenhouses (Tasgal, 2019). The Natural Resources Conservation Service (NRCS) has supported more than 9,825 high tunnels across the country since 2009 (“What…”, (n.d.)).
Growing in high tunnels requires farmers to perform many repetitive tasks. Chris Callahan of UVM Extension conducted a survey of winter growers that found row cover management takes an average of 0.4 labor hours per day per 30x96’ tunnel (Callahan, attached letter, 2021). Assuming a $20 per hour wage and 120 day winter growing season, farmers pay $960 per tunnel per year. NOFA-VT conducted a cost of production analysis for high tunnel tomatoes. Harvesting greenhouse tomatoes accounts for 17.1 labor hours per 1000 ft2 (“Cost…”, 2019). Using the same 30x96’ tunnels, harvesting tomatoes accounts for 49.25 labor hours per tunnel or $985 per tunnel per year.
High tunnel gantry systems (HTGS) can reduce repetitive tasks and physical requirements while saving time and enabling innovation. Existing large-scale commercial greenhouses use advanced automation to improve profitability and scalability. We are designing an affordable, accessible, and open source HTGS to allow small farms to benefit from similar innovation. We will support education and adoption of the system through farmer design reviews, demonstrations, research, and presentations.
The HTGS consists of one or more overhead rails, used as a monorail or together with a toolbar. Like a tractor, the toolbar works with interchangeable implements. A trolley car moves the implements along the rails to precise locations. We will develop two implements; a Transport Cart and an Automated Row Cover System (ARCS).
The Transport Cart saves farmers time and reduces the weight they must carry. Andy Jones of ICF anecdotally found they saved 40% of labor time using a similar rail and cart system to harvest tomatoes. Assuming $985 per tunnel per year for tomatoes, this equates to saving $394 per tunnel per year, not including time saved during transplanting, bed preparation and trellising.
The ARCS removes the daily task of managing row cover. We believe farmers can optimize the cover timing to increase ventilation, lighting, and temperatures for increased productivity and reduction of disease pressure. Saving both row cover management labor and tomato harvest labor, farms can save an average of $1,354 per tunnel per year.
The HTGS represents an effort to reduce the health risks and labor costs of repetitive heavy tasks, while improving crop yield and overall quality of life for farmers. Advancements in technology can provide new jobs and space to innovate, exciting the next generation of tech-savvy farmers.
Cooperators
- - Producer
- (Educator and Researcher)
- - Producer
- - Producer
- - Technical Advisor
- - Producer
Research
Objective 1 - Design
We have conducted a rigorous engineering design through two phases - a preliminary design and a critical design.
As we conducted designs, we reached out for feedback from our target community. We worked with the members of our Farmer Design Review board, conducted one on one interviews with 5 regional farmers, and presented the idea to two greenhouse manufacturers. We learned that, while not ubiquitous, it is reasonable to expect high tunnels of winter growers to contain truss-style supports and extra tall sidewalls, both largely due to winter snow load and tomato trellising. In addition, we determined that it is reasonable to design this system to run on AC power and have access to a wifi network. We determined that the Transport Cart must be less than 55 pounds, fit standard bins, and have an easy on/off to move from rail to rail.
Preliminary Design - sare_gantry_pdr_r03
At the preliminary design, we presented the concept and drafts of the mechanical, electrical and software designs. We broke the presentation into sections that explained each sub-system in detail such that the Farmer Design Review Board (FDRB) could provide feedback and critical direction.
Trolleys - Trolleys are passive rollers that allow you to hang and move items on the rail.
Rail System - Round tube hung from the high tunnel to allow hanging systems to move along the rail. The rail system is made from SS20 fence toprail. This is an accessible product available throughout the country. The ends are swaged, meaning they fit together, and are secured by two screws. The rails hang from Railex brand C-bracket that are supported to the high tunnel crossbars with a U-bolt. We chose the 5.5" C-bracket to ensure ample room for the trolleys to pass between the top of the tail and the bottom of the bracket.
Transport Cart - Hanging cart used to move objects. We presented our design for the Transport Cart. To keep the weight low, we modeled the cart out of aluminum. The review board noted that aluminum is challenging to weld and therefore would not be viable for most home fabrication efforts. They recommended we change to steel. Our original design fit a variety of harvest tote sizes, from bulk crates to bread trays. The review board recommended we keep the cart as narrow as possible rather than fit a wide variety of products. In addition, they recommended we change the frame supports such that farmers could easily load the cart from the front or back without reaching around the side.
Toolbar - Generic attachment to connect various implements between trolleys. The toolbar is a generic attachment point that connects the two rails and spans the width of the high tunnel. The toolbar was originally designed to hang from passive trolleys. We presented two styles - a fixed height model and an adjustable height model. To prioritize strength and simplicity, the review board recommended the fixed height. This model is adjustable at the time of the build, so could fit different high tunnels, but not adjustable once it is built.
Trolley Car - Motorized trolley that moves along the rail to move implements. The trolley car is a motorized box that drives the toolbar along the rail. We presented a concept that pushed and pulled the toolbar. The drive system comprises a NMEA 23 stepper motor and motor controller. We have geared this up almost 10x, bringing the total force to 27 newton meters, which we determined to be sufficient to push and pull the toolbar with implements.
Automated Row Cover System (ARCS) - Implement designed to automatically roll and unroll row cover. It includes spooling motors at both sides of the roll and a frame that attaches the implement to the toolbar. The system also has a motor box and that motor box includes the same components as the trolley car. We estimated that we could spool a 28.5' wide roll of remay in the 30' wide house.
The concept of operations broke down the steps to set up and operate the system components, including through the user interface to the software.
Critical Design - sare_gantry_cdr_r01
In the Critical Design Review, we presented the updated and final designs, including the mechanical drawings.
We lengthened the toolbar to lower the entire system which is best able to maximize the larger width of the high tunnel at lower heights. The final height of the toolbar will be determined during assembly.
The Trolley Car is no longer a free-hanging unit, but is now built directly into the toolbar. The weight of the toolbar and implement will provide better traction for the system. We designed a hitch that is made out of off-the-shelf springs and hardware and 3D printed parts. These attach to the Railex rolling trolleys and connect to the motor to create the drive system.
The major change to the ARCS was that we are now using self-aligned bearings. These will allow for sag in the spool.
We then discussed the materials cost and potential system issues for feedback.
Objective 2 - Build & Evaluate
We constructed a High Tunnel Gantry System (HTGS) for Jericho Settlers Farm. The construction process was divided into phases for rail, toolbar, and implement.
Rail Phase
We had originally selected a 100 x 30’ Ledgewood High Tunnel in which to build the system as that was the house in which we had built the first prototype. Because the house had underground heat, the farmers preferred to reserve that house for early warm weather crops rather than late winter greens, so we moved to a similarly sized Rimol. We hung the rail in November, but realized after installation that this house was not level, as is common in many high tunnels. The levelness of the house was not a factor we had greatly considered as slowing and braking were not a problem in the initial prototype. We elected to change houses once again to a 200’ x 30’ Rimol. As our budget only allocated 100’ of rail, we could only hang rail in the front half of the house. This house is also not perfectly level, but the grade was amenable to development of the ARCS.
We made the rails from 1 ⅜” standard fence SS20 round tubing with swaged ends and Railex hangers which are C-brackets with U-bolts. We used two rails to span the 30’ width of the high tunnel. The rails operate independently as a monorail or together as a system. The rails are installed over the high tunnel’s walking paths such that the Transport Cart can be pushed down the rows without impeding the crops.
The Railex brackets were hung every 8’. We found that distance is sufficient for smooth travel and overall rail load requirements. Optionally you can hang the brackets at 4’ if the cost is not prohibitive and high tunnel includes 4’ spaced supports.
We tested the trolley system to ensure the system can carry designed loads and move smoothly over junctions. We calculated that the trolleys would need to pull with a typical lateral force of less than 10 pounds. While the trolley’s passed smoothly over most of the junctions, it is critical that the swaged end fits snugly into the next pipe. Where there is a gap between outer diameter of the two pipes, the trolleys wheels can get hung up during travel.
Toolbar Phase
The toolbar was made from generic strut channel and extends about 28’ across the high tunnel. The toolbar provides a standard interface for implements. The toolbar hangs from both rails, hung by two sets of trolleys. The toolbar carries the ARCS but not the hanging cart.
The unistrut is connected by brackets and hardware. After hanging the toolbar, we speculated that the ARCS would hang too low to the ground so we shortened the vertical bars.
Implement Phase
The Transport Cart was made from welded steel 1” square tube and rail trolleys. We designed the Transport Cart to primarily carry 10-pound and 15-pound tomato flats. The steel cart weighs about 33 pounds so the system has a maximum load capacity of 225 pounds. The cart can carry twenty 10-pound flats or fourteen 15-pound flats. This cart can also be fabricated in aluminum which would allow the tool to remain unpainted. The aluminum cart would weigh 16 pounds. We chose steel to represent a product that others could more easily make or modify themselves as welding aluminum is a more specialized skill.
The Trolley Cars were made from 3D printed parts, motor, motor controller, drive wheels, sprocket, and chain. The trolley car includes an embedded computer to automatically control the trolley. The computer will run existing Rigorous software to control the system.
The ARCS was fabricated from standard round tube, self-aligning ball bearings, spooling motors, sprockets, and chains. The row cover system spans as much of the 30’ width of the greenhouse as possible, determined by the curvature of the hoops at the height of the implement.
The ARCS includes two motorized trolley cars to move the hanging implement down the rail. As the trolley cars move the ARCS, the on-board spooling motors roll and unroll the row cover onto a spool.
We tested the ARCS’ ability to effectively roll and unroll the row cover, the trolley car’s ability to move the ARCS, the system's ability to synchronize the two trolleys with rolling motors, and the system's ease of use.
We assembled most of the ARCS components off-site and put the components together at Jericho Settler’s Farm in January. We first tested the system without row cover. The self-aligning ball bearings had enough play to allow to wide pipe in the spool to roll easily even with a slight sag.
The trolley cars, as designed, were not effective in pulling the implement up and down the rail. The motor was mounted to the top piece of the toolbar. A chain connected the sprocket on the motor to a sprocket on the trolley car. When there was any motion in the toolbar with respect to the trolley car, for example a jiggle as it moves over a rail junction, the distance between the sprockets would contract and expand. This activity would pop the chain from the sprockets. We decided to redesign the trolley car such that the motor was attached to the trolley rather than the toolbar.
Once we redesigned and built the trolley car, we returned to swap assemblies. We used extra Railex trolleys to make cable trolleys for the extension cord. This allowed us to test running the system, unloaded, up and down the length of the rail. In addition, we coordinated the spooling motion of the ARCS motors with the trolley car motors.
We controlled the system through the browser-based app that we developed for the system. The runs off of the RGS software library with a specific instance and UI for this project. The User Interface allows the operator to turn the machine on in both automatic and manual modes. As we were testing basic functionality, we used manual mode.
In manual mode, an operator can direct the system to go forward, go backward, spool roll, spool unroll, or a combination of linear-direction and spin which is required to roll an unroll row cover. The buttons that operated all of the motors in tandem read “cover” and “uncover”. There is a stop button on every page.
Once the trolley cars and ARCS motors were working effectively, we loaded the ARCS with row cover for the first time. We found the added weight of the row cover was too much for the 28’ span of the spool and caused a significant bend in the spool. The bend in the spool caused a large moment on the spool, making it too powerful to rotate with the spooling motors.
We determined that the width of the tunnel was simply too long for the ARCS to work as expected. We discussed possible solutions and determined it would be possible to operate with a center support and two sections of row cover. To test, we folded the row cover over on itself and rewrapped it around the bar such that it covered about two thirds of the bar. We then used a strap to hold up the center of the spool bar. The strap allowed the bar to still spin freely while supporting the weight. This worked well and we were able to use the ARCS to roll and unroll row cover for the first time.
We then designed a center support system. This required us to cut the row cover into two pieces. The high tunnel had five beds when planted, so we cut the fabric to fit over 3 beds and 2 beds respectively.
We reset the row cover on the ARCS. The system was running quite well. We were able to roll and unroll the row cover along the full length of the rail. While there was a gap between the two sections of row cover, when the ARCS finished unrolling it often pulled it taut, closing the gap. We ran the system multiple times and documented the progress with photos and videos.
We then broke the system down so the farmers could till the high tunnel to plant early-season potatoes. We removed the ARCS from the toolbar. The implement is easily disconnected with the removal of 4 bolts.
Once the beds were ready, we reassembled the system. By this time, the daytime temperatures in the high tunnel were consistently in the 60s and 70s. We believe the temperature and humidity were showing us system problems that were not apparent during winter temperatures.
The trolley car glides up and down the rail with a rubber wheel. In the warmer and more humid environment, the wheel had trouble gripping the rail and would frequently spin out. This would cause the ARCS to get stuck and not complete the traverse down the high tunnel.
We came up with potential solutions to the rail grip problem. We decided to purchase adhesive sandpaper, hypothesizing that the grittyness would be sticky for the rubber.
Once the tape was adhered, we tried running the system again. Unfortunately, the tape made the grip issue worse. When the motors lost grip and began to spin out, the sand was ground off the sandpaper.
After further testing, we determined that we could not rely upon the ARCS to automatically cover and uncover the row cover without human intervention. We decided to break the system down and try to fix the trolleys off-site in our shop, shooting for a reinstallation next season.
We finished the design of the transport cart by incorporating the farmer feedback from the critical design review. We sent the design off to a fabrication shop and installed upon completion.
In November, 2022, we disassembled the ARCS at Jericho Settlers Farm. We moved the ARCS to the Rigorous warehouse in Williston. We designed and built attachment points for the rail and rebuilt the ARCS indoors.
Overall we feel we have made significant progress on identifying the system specifications, designing a solution to meet the requirements, and testing the design in the field. We found the design did not meet the required reliability, but through this process, we have identified the remaining technical challenges requiring a solution. In January 2023 we kicked off another round of design to address the remaining technical challenges to the system. We are planning to reinstall the next version of the ARCS into the high tunnel in March 2023.
Objective 3 - Research
The research objective will quantify the effectiveness of the HTGS by performing a labor analysis.
To test the labor savings of the ARCS, the farmers at Jericho Settlers Farm are tracking the labor required to move row cover in a comparably sized house that is in winter greens production during the month of February.
For the Transport Cart, we will host our test and control beds in the same high tunnel. Two beds with tomatoes will be on both sides of a single rail of the HTGS with the Transport cart. In the same tunnel, two beds with the same varieties of tomatoes will be on both sides of an open walkway. For two months during peak harvest and trellising, we will track data to compare labor time and harvest weights for the test and control beds. Jericho Settlers Farm will time sessions with and without the trolley. This will likely be 20 to 24 harvest sessions and 10 pruning sessions.
We will analyze the results and prepare a summary report that we will make publicly available. We will calculate total seasonal labor savings estimates based on these trials. We will also quantify the reduction of carried weight, calculated by collecting harvest data weight data over the average distance of travel.
Objective 4 - Education & Adoption.
We will host plans, designs, and instructional content online. Instructional content will be created during all phases of this project and will cover best practices for installation, testing, and use. The content will be in a variety of formats, including video and written articles.
We will host two on-farm workshops where we will demonstrate the system. We will record the sessions for farmers to view online. We will cover the installation, load constraints, and best practices of the system. Through these workshops, participants can test drive the implements and ask questions directly.
To measure achievement of this project, we will track the following metrics.
To quantify education:
- Number of design downloads
- Supporting materials content views
- Attendees of demonstrations
To quantify adoption and farmer benefit:
- Number of new systems installed
- Labor hours saved as reported by farm partners
- Reduction of carried weight, calculated by collecting harvest weight data over average distance of travel
Education & Outreach Activities and Participation Summary
Participation Summary:
We have begun one on one interviews to determine feasibility and desirability of the High Tunnel Gantry system. We toured and interviewed Mira and Dakota Miller of Row by Row Farm (Hurley, NY), Tony and Joie Lehouiller of Foote Brook Farm (Johnson, VT), and Paul and Sandy Arnold of Pleasant Valley Farm (Argyle, NY). We also received general feedback from farmers at Intervale Community Farm (Burlington, VT) and Ardeen Farm (East Aurora, NY).
We looked to understand current season extension activities, barriers to winter production or expansion, infrastructure, and use of new or unconventional technologies.
We hosted a preliminary design review and a critical design review for the Farmer Design Review Board which has set us up to construct the system in January 2022. We will test the system for about one month and will then schedule an on-farm workshop and demonstration that is open to the public.
We have started to post regularly to our Instagram account. This includes the creation of graphics from our design files. We have posted designs for feedback as well as shorts of us constructing components of the system (images below) and recaps of farm tours. While this project is not the only thing we post about on the @rigoroustech account, we have reached 10.7K accounts in the last 90 days. We have 190 followers, the majority of which are farm or food system-based accounts. Project-related posts have reached up to 627 accounts each with up to 41 likes and 12 comments. We regularly receive a handful answers to posed questions, mostly asking about growing practices and soliciting design feedback.
We hope to leverage this channel to drive awareness to the workshops and digital resources. We wrote a blog that summarizes the project and plan to continue to write blogs and tutorials. https://www.rigorous.co/blog
During the design and development stages of the High Tunnel Gantry, we engaged a number of farmers for feedback and to gauge general interest. Some of the interviews were held by the principal and those included farm tours and in-depth discussions. Many of the interviews were held by a group of University of Vermont MBA students through a volunteer consulting project. Those interviews were held on the phone and typically lasted about 15-30 minutes.
We had a standardized set of questions for each farmer interview in order to understand how many farmers had the infrastructure and growing practices that could benefit from the High Tunnel Gantry. Those questions included:
- Do you have (a) high tunnel(s) or greenhouse(s), if so, how many?
- Do your greenhouse/high tunnel structures have access to electricity?
- Do your greenhouse/high tunnel structures have access to wifi?
- Do you do winter production or season extension?
We also asked farmers about their opinions about open source technologies, their production focus, the task they’d love to automate, and solicited feedback on the designs of the ARCS and hanging cart.
|
Question |
Response |
Range |
|
Do you have (a) high tunnel(s) or greenhouse(s), if so, how many? |
100% Yes, n=19 |
1-20 |
|
Do your greenhouse/high tunnel structures have access to electricity? |
94% Yes, n=19 |
The “no” expects to have electricity by Spring 2023. Many responded that some, but not all, houses have electricity. |
|
Do your greenhouse/high tunnel structures have access to wifi? |
21% Yes, n=19 |
Some have wifi but it doesn’t reach the entire farm, some use IMonnit System to connect to home router, some could add boosters if necessary. |
|
Do you do winter production or season extension? |
76% Yes to season extension or winter production; 48% Yes to winter production, n=21 |
Infrastructure
All farmers had at least one high tunnel or greenhouse on their farm. Almost every respondent indicated that they had electricity in at least one high tunnel or greenhouse. Some, such as Cate Farm, have electricity in all houses in order to operate HVAC, alarms, fans, and temperature sensors. Others, such as Row by Row Farm, have electricity in the main houses but not in houses in the back fields. The only respondent who indicated that they did not have electricity in any high tunnel has plans to implement in the Spring of 2023. This does not appear to be a barrier.
Wifi dooes appear to be a barrier for the majority of farmers. While some farmers have options to boost wifi signal to specific areas of their farm, the vast majority did not see a path to bringing wifi to their high tunnels. Many who did have wifi noted that it was not reliable.
The vast majority of farmers (76%) do some sort of season extension. Only 48% of respondents grow during the winter. Of those who do, many grow spinach, kale, chard, and pac choi. Some of these farmers are scaling down winter operations or plan to grow only crops that over-winter until the Spring. Farmers indicated that effective management of temperature and humidity was a barrier to winter production. Many farms grow early and late season crops in their high tunnels in the Spring or the Fall. Crops grown include beets, carrots, lettuce, potatoes, onions, and greens.
ARCS Feedback
One hypothesis that we wanted to test was whether managing row cover was a pain point for many Northeast farmers. Some farmers, including the teams at Sunrise Farm, Pleasant Valley Farm, Good Heart Farmstead, and Ardeen Farm have scaled back winter production in recent years. Edge of Good Heart Farmstead relayed, “we’ve stopped growing winter greens entirely because we dislike row covering so much.” Other farmers indicated that winter production was too much work for the off-season, still others are transitioning their farms and decreasing specialty production as they do so. We have heard farmers express that row cover was at one time a major pain point for them but they stopped managing it intensively or at all. Danielle from Root 5 Farm noted, “different veggies require different row coverage timing throughout the winter season and they do not consider row cover to be that labor intensive”.
Some farmers believed that automated row cover systems would save time. Some would be interested in an outdoor row cover system, others would be interested but do not plan to put resources towards such a project, wondering if the setup time and expense would create a positive return. Cara of Evening Song Farm said, “we would expect a major investment to pay back within 3 years, but beyond that, it’s an improvement to the quality of life for them. We hate doing row cover and have even considered not growing greens because of it.” A farmer at Evening Song Farm noted that managing row cover takes about 80 labor minutes to manage row cover each day and is a task that makes staff grumpy. Elmer Farm noted that management of row cover would only be applicable for 3-4 months of the year and the cost would have to show a clear return on investment. Overall, we found that farmers were generally interested, but our hypothesis that row cover is a major pain point was not confirmed. Many farmers expressed appreciation that engineers were working on products for small farms.
Transport Cart Feedback
Farmers overall were interested in the transport cart. They appreciated the simplicity of the system and that it does not take up any floor space inside their high tunnel or greenhouse. The farmers at Foote Brook Farm thought that a ladder attachment would be especially useful for hanging tomato trellises. The farmers at Jericho Settlers Farm would be interested in an adjustable transport cart that could adapt to different functions and be inexpensive. They also suggested a wheel on the bottom such that the cart could take heavier loads than the high tunnel’s frame may support without causing damage.
Opinions on Open Source Technologies
Some farmers love the idea of open source technologies. Those farmers tend to feel comfortable with do-it-yourself assemblies, retrofitting older technologies to new systems, or fixing machinery in-house. Other farmers did not care about the technology being open source, some thought that the technology would be untested and unreliable. I believe all farmers who have shown interest would only be interested in a functional product; no farmers expressed interest in continuing to develop or tinker with the technology themselves.
Opinions on Automation
Quite a few farmers were interested in automation in general, but not “tech for tech’s sake”, as a farmer at Boneyard Farm expressed. Farmers easily thought of ideas for tasks that they would automate on their farms, and the views were quite diverse. We did not ask what each farm paid their staff, but some shared that general labor rates were as high as $20-$25/hour. This makes farmers want to focus their staff on high value tasks rather than time-intensive monotonous tasks that could be done by a machine. Ideas included:
- Shredder and mixer to spray mulch
- In row weeding for small scale farms
- Watering, irrigation
- Moving clear plastic for weed capturing
- Washing and drying
- Greenhouse side rollups, vents, temperature controls
- Night curtains
- Seeding flats
- Mower
Learning Outcomes
Thus far, we have shared detailed information with our collaborators (4 farmers) and the farmers we have had one on one interviews with (8 farmers, 4 farms). These farmers now have a deep understanding of the system we seek to build and have been able to provide critical feedback to influence the designs. They have also been able to conceive of additional ideas for the high tunnel gantry, displaying understanding of its potential in their operations.
In addition, we have reached surveyed 20 additional farmers and shared details about the program.
Project Outcomes
Not Yet Available.
Not Yet Available.
Information Products
- High Tunnel Gantry Preliminary Design (Conference/Presentation Material)
- High Tunnel Gantry Critical Design (Conference/Presentation Material)