The BOM Increase

If I’m understanding correctly, a BOM increase is happening. I’m not sure if this was brought up, but an advantage of the increase is that karts won’t need grand father status. Any kart ever built should fit under the new bom limit. I think this makes things simpler.


We were discussing this at the summit and it turns out that in $500 in 2009 is equal to $655.24 today when adjusted for inflation. I think the big question is whether the increase will stifle or expand people’s creativity/ingenuity in any particular build. We’re going to temper the increase with a “cheapskate moxie bonus” for the cheapest build for the weekend.

Hmm, I’m a bit torn about it honestly.

I mean honestly while inflation has gone up and certain parts of the BOM have gone up accordingly. Other major pieces such as motors, controllers, and batteries are actually cheaper to source these days than in 2009. Overall I’m not really convinced it’s any harder to build to the BOM cost in reality.

I’m guessing this will stiffle the engineering creativity for the sake of making it easier for people to build (and hopefully attract more people).

I also agree with Andrew. If this does go through we need to force everyone to re-evaluate their BOM cost under current day FMV. We can’t have someone using 2009 costs for materials while claiming the 2022 BOM allowance.

1 Like

We could remove the wording for “grandfathered in” costing on the ruleset, I would bet that no one would be affected.

1 Like

Yea I just looked and the only place grandfathering is mentioned is with respect to battery FMV.

And that is definitely an area which I think we should eliminate. It’s so much easier to enforce the cost per watt-hour and with the BOM increase there is zero excuse for having to be grandfathered. In particular those running Nissan Leaf modules should properly calculate their true BOM cost based on 7 cents per watt-hour. Leaf cells already had an unfair advantage on the BOM. We can now correct this and with the overall BOM increase Leaf people still are getting a huge bump and will end up with more margin on the BOM than before anyways

Another thought I had in general besides just arbitrarily changing the BOM limit was to flat rate batteries at a lower level per watt hour.

Truth be told it’s actually pretty easy these days to find battery setups for under $0.10 per watt hour. Therefore half FMV these is actually lower than 7 cents. When I did the math last it seemed like 4.5 cents per watt-hour was a more appropriate 50% FMV value. I would think going to something like that with either a small (or even no) bump in BOM limit is fine.

TBH karts these days can be made under the $500 limit pretty easily, especially at 4.5 cents per watt hour. A $200 overall bump in the limit is absolutely huge. Maybe something like 4.5 cents per watt hour and $600 limit?

The only thing budget related that I think didn’t get covered on the Summit (or previous Summits, at least that I can recall) is: how do you assess FMV on a portion of a thing? This is very common in the rulesets for other budget racing, like LeMons or Chump car, which also have a kinda-sorta-$500 budget limit.

In their case, assume you buy a Corolla for $500 but you add a $200 widget. New budget $700! However, you can sell the radio, you can sell the rear seats, you can sell the gas tank, etc, to earn back budget.

In PRS way back in 2014/2015, I recall a couple teams doing this and having Jim’s blessing, ie, buying an ebike or an electric scooter on craigslist and then selling the wheels and other parts they dont need. I think it’s fair that if you bought an entire ride-on lawn mower to harvest the rear differential and you sell the engine etc that you should only assess the REMAINING VALUE as the FMV on the components you actually use.

What are our thoughts on this? Could be very important for some builds, and if anything encourages the cheapskate builds.

1 Like

I’ve thought that you only count the value of the part you’re using, not counting any sell-off math. However, on things like steel - If you buy a 10ft piece of steel tube for $10, and only use half, then you only count half. But if you buy a whole ebike, and only use the motor, then you only count the motor value, without any further reduction.

1 Like

Hi everyone new the forum here, love it by the way begone with facebook. I think the budget increase makes sense, its going to eliminate the “grandfather BS”, which was something I never liked. The biggest killer for most peoples budget seemed to be battery, especially those with bigger leaf of volt packs. This should most def allow for everyone to follow the 7c/KW. And use any existing batteries they have. One of the topics in the first place with the cents per Watt hour was, what’s the number 4.5c , 6c, 7c? Either a lower number like 4.5 cents and keep the $500 because that’s the spirit of the league, or a higher number like 7c and do the higher 700 budget. FMV seems to always be clear cut to me, but somehow battery cost got mixed into this a few years back, I feel like that was mostly because people were getting their leaf cells at various different Prices depending on whatever variables or deals were around, and to be fair to everyone a value got picked that made sense to all. The only question I have is how do you fairly calculate the actual watt hours on a given pack, considering battery degradation. My leaf pack, I know what it should hold, but what does it actually hold after all these years and charge cycles? The one thing I personally like about the budget increase is that I think it will allow for people to be able to try other things, that trying to make the budget may have cut out or left out. I for one know I could use another $40-50 bucks to upgrade my cooling system or add beefier steering… The bottom line is The Actual out of pocket cost is the same regardless of how the BOM is fudged. So if the $500 BUDGET was truly that important to the spirit of the league and people still wanted to do wild stuff you could make 3 cents per hour. That’s what I honestly think it comes down to, and if so Id vote for a lower watts per hour number and keep the 500 budget.


@techguyking Charging for the portion you consume of a thing like steel is pretty clear cut on the BOM. FMV of 1 foot of tube that you bought a 10 foot piece for $100 is easy enough. But what % of the value of a used ebike is the controller? If there’s no established FMV calculation, then how does someone assess the value? The sell-off technique has pros and cons:

-allows creativity in sourcing parts. Some parts may not be available, or may not be available at reasonable BOM cost, if you have to buy them separately. Just think if Leaf packs weren’t available unless you bought a crashed Leaf! You would want people to be able to use them, but if they had to charge the entire cost of a salvaged Leaf, that wouldn’t be possible.
-allows people to recoup actual IRL $$$, not budget cost. If we want this to be a “cheap” league and open to as many people as possible with various financial means, then allowing someone to buy and then sell parts makes some sense

-Just like anything in Finance (haha), this could be abused. What if someone buys a thing for $500, and then sells everything but what they need for $700? Did that thing cost them negative $200?

If a sell-off technique is desired, you’d certainly want a lower floor to it, ie, if you buy a $500 thing, no matter what you do at least 5% of its cost is retained OR the thing you use cannot be assessed at less than 50% of FMV comps (ie, find sold items on EBAY and assess at no less than 50% of that). I’m not sure how to handle this concept.

As an aside for @techguyking 's comment: What is the FMV of a 1 foot of square tube? Say you can buy it in 12 foot lengths at metal depot, but you ACTUALLY bought it in 1 foot length through mcmaster because it was convenient to do so. Per foot value from metal depot might be $1/ft, but $5/ft through McMaster. Do we care where someone gets it? Can they legally assess it on their BOM for $1/ft? Would it be reasonable to let someone assess it at the cheaper value as long as it is an apples-apples comparison, ie, the cheapest you can find it from an online store that would ship it, just not necessarily mcmaster?

1 Like

Re: metal pricing.

When I buy steel from my local shop, its sold by the pound anyway. So one could use the per-pound price? I’m also a big proponent of if I bought it once (retail, not shady side deal) at $50, that part is always $50 on my BOM if I replace it.

If you’re trying that hard though, you’re trying too hard.

With the sale of cost of parts… again. are you just trying too hard. We’re all limited to ~1500w anyway. That’s what hopefully levels the playing field.

Radical idea. Do away with the Budget/BOM entirely. No limits. but, be very strict on the fuse requirements, and mandate a set of off-the shelf holders to go with the fuses. Maybe give some bonus for cars that make it under the “budget”. Also would have to be more strict on the “must look like a power wheels” requirement, to prohibit all out gokarts.

EDIT: Instead of doing away with the BOM entirely, just limit what does count on the BOM
Leave it at some $$ Value, but make it something like, Motor + Controller + Batteries + Frame or something like that. Pricing for individual components is what they could be purchased for (reasonably) from ebay or the like, or whatever you paid for them. In the case of the "motor controller from an ebike that you sold the rest of, find a similar controller on ebay and use that as the price.

Changing the announcement to “Limited to 1500 watts of power” instead of “built for just $500” is more truthful, and also is easy enough to say. Plus, you can relate 1500w to common household appliances, like a hair dryer or vacuum cleaner. “These cars achieve speeds of up to 30mph, all while limited to less power than your vacuum cleaner!”

I am torn about doing away with BOMs totally. I know when I was starting they were invaluable for seeing how to make a kart.

I think this discussion gets into what is the purpose of the BOM? I assumed it is to help new teams learn, keep prices low so the series is accessible, keep try hards out, force creative solutions, and make the karts unreliable so the show is better.

In my opinion, we need a way of trying to steer people towards the spirit of a low priced kart. Stressing over how FMV is calculated is the opposite of that.

This is definitely a tough, problem. I think one way of steering people is through moxie points. There could be tiers of moxie points you get for submitting your bom: 0 pts for no bom or way over, 50 points for believably around $500, and 100 points for believably under $500. Not exact values, but basically make it crippling if you don’t follow the spirit of the rules and a reward if you are super cheap.

Idea. Submitting a BOM lets your points count (as is written now, both moxie and Race Points) and “budget” as $500

Every Kart starts with a ~200? point (moxie) budget bonus. For every dollar over $500 on the budget, as calculated using the current values, the points are reduced by the same amount.
(I.e. you spend $650 on your kart, you only get 50 extra points)

We could implement this as-is, or we could reduce the per-race event moxie points from 400 to some lower value. So that this value counts more.

Is this too complicated? thoughts?

This topic came up in a summit a few years ago. You explicitly cannot subtract the cost of sold bits from the purchase price of the whole item. You have to FMV the component you used. I believe this was discussed specifically with respect to Waffle Kart, which was admitted to be way over budget without this subtraction technique. So, I want to see cool karts like Waffle Kart.

1 Like

That sounds haaaaaard

not really as for as points/scoring would go. it only has to be calculated once per kart/season. And, it still rewards cheaper builds directly, while “allowing” more expensive builds. I do think it would require a rebalance of moxie points overall though.

My $0.02

Doing away with the BOM and calling it 1500w series is two bad decisions. Throw away the BOM and stuff would get crazy. Stupid expensive controllers, exotic materials, etc. just to have a little leg up. Then in terms of marketing "we race 1500w karts power wheels " isn’t half as catchy and intriguing as “we race $500 diy power wheels”.

As for the negative deduction thing. Like other have said it’s just an abuse. If you have trouble determining the FMV of a controller from a used electric lawnmower or something just be reasonable. Look at the approximate value of that item relative to the whole thing then scale it for what you paid. Or just use the price of a similar off the shelf piece. Or simply post up a proposal asking what people think a reasonable value is. In the end it’s not negative $50, you know that and the rest of the community knows that.

Moxie points for BOM submissions is a great idea IMO. It makes everyone want to submit ideas, encourages diy (and associated creative and shitty ideas), and makes people’s builds transparent.

All-in-all I think the latest changes were all very good so kudos to what came out of the summit. I don’t think we need to overthink too much here. All in all I tend to agree with Caveman the most my favorite proposition is to reduce the battery cost in watt-hours and keep it as close as possible to a $500 BOM limit. That is the most accurate representation of value as well as the best optics for the series.

In short I feel these are the best options:

  1. Remove grandfather clause, set to 4.5 cents per watt hour and make it a “$599 BOM”
  2. Remove grandfather clause, reduce battery cost even further and keep it at $500 BOM. In fact, far as I care simplify and say batteries are free on the BOM. I.e. It’s a “$500 BOM excluding safety items and batteries.”
  3. Remove grandfather clause, keeping the ruleset otherwise exactly how the summit set it. Honestly $200 is a pretty obscene increase in my book, but still I like the simplicity of watt hours.
1 Like

What murry said !!!

So i’ve been thinking about this still, as I want to close up the rules and publish them as the 2022 “official” set.

I really want to keep the battery price on the BOM, at least in some way. I believe balancing the creativity of battery capacity and price makes for an interesting endurance race. Some teams switch batteries, some teams run big one, etc… and it makes thigs more interesting. The reason for moving the battery price to $ per wh instead of “1/2 FMV” was to alleviate confusion and level the playing field a bit, and allow the use of “safer” battery technologies for teams less willing to play with taking apart a Volt/Leaf cell or homebrewing some LiIon solution.

I also agree that a $500 limit even with budgets as-is is difficult with inflation and with this whole parts-shortage world we live in. That’s why I was okay with the increase initially, but after thinking about it, and agreeing with others, $200 extra is a big deal.

I think a modification of @WhatsADSM 's first proposal is maybe the best option.

  1. Remove grandfather clause, set to 4.5 cents per watt hour and make it a “$599 BOM”

Change to

  1. Remove grandfather clause, reduce slightly to $0.06 per watt hour, and make it $600 BOM.

This balances the cost of things going up, without blowing budgets to the sky-high range of $700. It also still forces innovation and thought when it comes to battery capacities. For some teams, just moving the battery cost to $$/watt-hour will give them many extra dollars as-is.