Human Electric Trike Thesis

Design of an electrically assisted human powered trike

Archive for the ‘Components’ Category

New A-Arms

Posted by Bob Dold on Saturday, November 18, 2006 10:21 PM

The first test runs I did on the trike resulted in a bent lower right a-arm, I straightened the a-arm out as best as I could after each incident but it was apparent the a-arm was not strong enough.

The original a-arms were made from .405 diameter by .068 wall 6061-T6 aluminum with a yield stress of 15,000 psi. While the stress analysis of the arms did not show any problems, the testing must have produced a load case not accounted for in the analysis. I also noticed the right rocker arm was not moving freely which may have restricted the shock movement, putting undue stress on the a-arm. Whatever the cause of the bending, it was apparent the arm needed to be stronger. A search of McMaster found a .500 diameter by .120 wall 2024-T3 tubing with a yield stress of 45,000 psi – this will be more than 3X stronger than the original tubing. The only downside is this tubing is much more expensive than the original tubing, almost $10/ft vs. $1/ft. Because the OD is close to the old tubing size I will be able to use the existing pushrod mount by boring it out to .500 diameter and bonding the new arms in.

The above pictures show the new a-arm on the right compared to the old one on the left, you can also see how much thicker the wall is on the new part.

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Fabrication pictures

Posted by Bob Dold on Sunday, October 22, 2006 11:10 PM

Spent about 20 hours this week assembling the frame, the process consists mostly of loctiting a joint, letting it set overnight and then moving on to the next joint. The assembly has to be put together in a certain sequence or the parts will not go together. To start I put together the rear of the frame as shown below, using the waterjet cur seat tube support to space everything correctly.

    

After the rear section was put together I assembled the front bulkhead. I cut 3/8 tube spacers to space the plates apart about 1.285 to allow clearance for the front suspension rocker arms to swing freely.

At this point I connected the front and rear sections using the longitudal frame rails which had their suspension mounting blocks already bonded on:

The completed frame assembly is shown below, at this point the mounting holes for the suspension rod ends need to be drilled and tapped to accept the control arms. So far I had only one bonded joint fail – this happened when I had to use a mallet to pound the lower frame rail into place through the tight fitting bulkhead – loosening the rear block where the swingarm will mount. I removed the block and rebonded a new one – I think the large impact loads from the hammer caused the joint to fail, in actual use none of the joints should see axial impact loads of the magnitude the failed joint saw.

Frame assembly ready for tapped holes and suspension mounting:

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10-15 Dry fit

Posted by Bob Dold on Sunday, October 15, 2006 9:03 PM

  Took some of the bonded parts I put together yesterday and did a dry fit with the parts I have completed. The batteries are sitting in their position between the frame rails.The shock is shown in it’s installed postion connected to the bellcrank.

 

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10-13 Received parts

Posted by Bob Dold on Friday, October 13, 2006 8:57 PM

 Received all waterjet parts from BigBlueSaw yesterday and picked up majority of machined parts from Pete at the WNEC shop. The picture below shows most of these parts laid out:

 

The plan is to bond together what I can over the weekend to be ready for the unfinished parts when they are completed.

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Fabrication progress

Posted by Bob Dold on Friday, October 13, 2006 9:19 AM

Stopped in to see Pete this morning to check on progress, he has completed the majority of the parts, the chart below shwos the parts left to complete:

Remaining parts should be complete in the next two weeks.

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Fabrication Status

Posted by Bob Dold on Saturday, September 30, 2006 3:36 PM

Fabrication of components is progressing ahead of schedule, the spreadsheet below shows the status of the parts that have been completed and those that are left to build:

On Friday I went into the shop and cut most of the tubing to length for the frame rails and rear swing arm. I also did the the bonding of the lower a-arm assemblies using the Loctite 680 as the adhesive. Bond prep consisted of  cleaning with Scotchbrite and then wiping with Acetone and then applying the green adhesive. The 680 took about 15 minutes to set and seemed to completely cure in about 24 hours. The pictures below show the lower a-arm and the sides of the swingarms bonded together:

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Water jet part quote

Posted by Bob Dold on Saturday, September 30, 2006 3:02 PM

Found an online waterjet cutting service that provides instant quotes for cutting parts from a DXF file: www.bigbluesaw.com. I arranged all my 1/4″ aluminum plate parts I need made into an assembly file and nested them together to reduce the material needed. I then uploaded it to Big Blue Saw and they provided the following picture of the cut parts:

Their online software automatically identified the 22 parts and provided the following quote:

Delivery is 2-3 weeks.

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Received Stealth 1000 scooter

Posted by Bob Dold on Thursday, September 21, 2006 10:28 PM

I received the Schwinn Stealth 100 scooter today and assembled it and then took apart the rear wheel drivetrain to measure the motor/gearbox. I was able to remove the wheel ad motor assembly after removing 12 screws and then tapped the wheel off the gearbox shaft. the wheel was keyed to the 12 mm shaft with a 4mm key. After removing the motor guard/mount I weighed the assembly and took of the gearbox cover to inspect the gears. The gearbox uses a 10 tooth pinion, 58 tooth idler gear , and 68 tooth drive gear for an overall reduction of 6.8:1. The gears are packed with grease as shown in the picture below:

Several other Stealth 1000 owners posted  that they replaced the grease with oil to get a quieter geartrain, although I didn’t think it made much noise on my first test drives. The next picture shows the gearbox with the guard/mount removed, this assy weighs about 9 lbs.

After measuring the gearbox I created a SolidWorks model of it and started trying to fit it into the rear frame:

After evaluating various methods for getting the gearbox power to the rear wheel I settled on driving a 5 speed cassette mounted from the swingarm with a 14 tooth freewheel on the gearbox output shaft. With this driving the 38 tooth cog on the freewheel I will be able to gear down the motor enough to drive the 7 speed rear cassette at the same speed as the rider’s cadence.

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S1000 Motor pics

Posted by Bob Dold on Tuesday, September 19, 2006 1:07 PM

Here are some pictures I found on the web of the Currie 1000 Watt motor that will be used on the trike, I should have the real thing on Friday 9/22:

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Odyssey PC925 Battery

Posted by Bob Dold on Saturday, September 16, 2006 8:34 PM

Because the Optima D51 batteries are no longer made, the Odyssey looks to be the next best choice to fit in the frame – with the 1000 watt currie motor three will be required. Available from http://www.batteryweb.com/odyssey-detail.cfm?Model…

Odyssey Batteries PC925

PC925

Voltage: 12 V  
CA: 925 AH
CCA: 470 AH
AH: 27  
Warranty (years): 3
Hardware: M6 – Female Brass
Replaces: Unique
Weight: 26 Lbs
Length: 6.5
Width: 7.0
Height: 5.0

Price: $98.88

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